National Instruments Labwindows Cvi Standard Livraries 320682C Users Manual LabWindows/CVI Libraries Reference

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LabWindows /CVI
Standard Libraries
Reference Manual

July 1996 Edition

Part Number 320682C-01

© Copyright 1994, 1996 National Instruments Corporation.
All rights reserved.

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Contents
_____________________________________________________________________________

About This Manual...........................................................................................................xvii
Organization of This Manual .......................................................................................xvii
Conventions Used in This Manual ...............................................................................xix
The LabWindows/CVI Documentation Set .................................................................xx
Related Documentation ................................................................................................xx
Customer Communication ...........................................................................................xx

Chapter 1
ANSI C Library ................................................................................................................1-1
Low-Level I/O Functions .............................................................................................1-2
Standard Language Additions ......................................................................................1-2
Character Processing ....................................................................................................1-5
String Processing..........................................................................................................1-5
Input/Output Facilities .................................................................................................1-6
errno Set by File I/O Functions ....................................................................................1-6
Mathematical Functions ...............................................................................................1-6
Time and Date Functions .............................................................................................1-6
Control Functions.........................................................................................................1-7
ANSI C Library Function Reference............................................................................1-9
fdopen...............................................................................................................1-9

Chapter 2
Formatting and I/O Library ........................................................................................2-1
Formatting and I/O Library Function Overview ..........................................................2-1
The Formatting and I/O Library Function Panels ............................................2-1
The String Manipulation Functions .................................................................2-3
The Special Nature of the Formatting and Scanning Functions.......................2-3
Formatting and I/O Library Function Reference..........................................................2-4
ArrayToFile......................................................................................................2-4
CloseFile ..........................................................................................................2-7
CompareBytes ..................................................................................................2-7
CompareStrings................................................................................................2-8
CopyBytes ........................................................................................................2-9
CopyString .......................................................................................................2-10
FileToArray......................................................................................................2-11
FillBytes ...........................................................................................................2-13
FindPattern .......................................................................................................2-13
Fmt ...................................................................................................................2-14
FmtFile .............................................................................................................2-15
FmtOut .............................................................................................................2-16
GetFileInfo .......................................................................................................2-17

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GetFmtErrNdx..................................................................................................2-18
GetFmtIOError .................................................................................................2-18
GetFmtIOErrorString .......................................................................................2-19
NumFmtdBytes ................................................................................................2-20
OpenFile ...........................................................................................................2-20
ReadFile ...........................................................................................................2-22
ReadLine ..........................................................................................................2-23
Scan ..................................................................................................................2-24
ScanFile............................................................................................................2-25
ScanIn...............................................................................................................2-25
SetFilePtr..........................................................................................................2-26
StringLength.....................................................................................................2-28
StringLowerCase..............................................................................................2-28
StringUpperCase ..............................................................................................2-29
WriteFile...........................................................................................................2-29
WriteLine .........................................................................................................2-30
Using the Formatting and Scanning Functions ............................................................2-31
Introductory Formatting and Scanning Examples............................................2-31
Formatting Functions .......................................................................................2-32
Formatting Functions—Format String.................................................2-33
Formatting Modifiers ...........................................................................2-35
Formatting Integer Modifiers (%i, %d, %x, %o, %c)..............2-35
Formatting Floating-Point Modifiers (%f)...............................2-37
Formatting String Modifiers (%s) ............................................2-38
Fmt, FmtFile, FmtOut—Asterisks (*) Instead of Constants
in Format Specifiers .............................................................................2-39
Fmt, FmtFile, FmtOut—Literals in the Format String.........................2-40
Scanning Functions ..........................................................................................2-40
Scanning Functions—Format String....................................................2-41
Scanning Modifiers ..............................................................................2-43
Scanning Integer Modifiers (%i, %d, %x, %o, %c).................2-43
Scanning Floating-Point Modifiers (%f)..................................2-45
Scanning String Modifiers (%s)...............................................2-46
Scan, ScanFile, ScanIn—Asterisks (*) Instead of Constants
in Format Specifiers .............................................................................2-48
Scan, ScanFile, ScanIn—Literals in the Format String .......................2-48
Formatting and I/O Library Programming Examples ..................................................2-49
Fmt/FmtFile/FmtOut Examples in C ...............................................................2-50
Integer to String....................................................................................2-50
Long Integer to String ..........................................................................2-51
Real to String in Floating-Point Notation ............................................2-51
Real to String in Scientific Notation ....................................................2-52
Integer and Real to String with Literals ...............................................2-53
Two Integers to ASCII File with Error Checking ................................2-53
Real Array to ASCII File in Columns and with Comma Separators ...2-53

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Integer Array to Binary File, Assuming a Fixed
Number of Elements.............................................................................2-54
Real Array to Binary File, Assuming a Fixed
Number of Elements.............................................................................2-54
Real Array to Binary File, Assuming a Variable
Number of Elements.............................................................................2-55
A Variable Portion of a Real Array to a Binary File............................2-55
Concatenating Two Strings ..................................................................2-56
Appending to a String ..........................................................................2-56
Creating an Array of File Names .........................................................2-57
Writing a Line Containing an Integer with Literals to
the Standard Output..............................................................................2-58
Writing to the Standard Output without
a Linefeed/Carriage Return ..................................................................2-58
Scan/ScanFile/ScanIn Examples in C ..............................................................2-59
String to Integer....................................................................................2-59
String to Long Integer ..........................................................................2-60
String to Real........................................................................................2-60
String to Integer and Real.....................................................................2-61
String to String .....................................................................................2-62
String to Integer and String ..................................................................2-63
String to Real, Skipping over Non-Numeric Characters
in the String ..........................................................................................2-63
String to Real, After Finding a Semicolon in the String ......................2-64
String to Real, After Finding a Substring in the String........................2-64
String with Comma-Separated ASCII Numbers to Real Array ...........2-65
Scanning Strings That Are Not NUL-Terminated ...............................2-65
Integer Array to Real Array..................................................................2-66
Integer Array to Real Array with Byte Swapping................................2-66
Integer Array Containing 1-Byte Integers to Real Array .....................2-66
String Containing Binary Integers to Integer Array.............................2-67
String Containing an IEEE-Format Real Number
to a Real Variable.................................................................................2-67
ASCII File to Two Integers with Error Checking ................................2-68
ASCII File with Comma Separated Numbers to Real Array,
with Number of Elements at Beginning of File ...................................2-68
Binary File to Integer Array, Assuming a Fixed
Number of Elements.............................................................................2-69
Binary File to Real Array, Assuming a Fixed Number of Elements....2-69
Binary File to Real Array, Assuming a Variable
Number of Elements.............................................................................2-69
Reading an Integer from the Standard Input ........................................2-70
Reading a String from the Standard Input............................................2-70
Reading a Line from the Standard Input ..............................................2-71

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Chapter 3
Analysis Library ...............................................................................................................3-1
Analysis Library Function Overview...........................................................................3-1
The Analysis Library Function Panels .............................................................3-1
Hints for Using Analysis Function Panels ...........................................3-3
Reporting Analysis Errors................................................................................3-4
Analysis Library Function Reference...........................................................................3-4
Abs1D...............................................................................................................3-4
Add1D ..............................................................................................................3-5
Add2D ..............................................................................................................3-5
Clear1D ............................................................................................................3-6
Copy1D ............................................................................................................3-7
CxAdd ..............................................................................................................3-7
CxAdd1D .........................................................................................................3-8
CxDiv ...............................................................................................................3-9
CxDiv1D ..........................................................................................................3-10
CxLinEv1D ......................................................................................................3-11
CxMul ..............................................................................................................3-12
CxMul1D..........................................................................................................3-12
CxRecip............................................................................................................3-13
CxSub ...............................................................................................................3-14
CxSub1D ..........................................................................................................3-15
Determinant......................................................................................................3-16
Div1D ...............................................................................................................3-16
Div2D ...............................................................................................................3-17
DotProduct .......................................................................................................3-18
GetAnalysisErrorString....................................................................................3-19
Histogram .........................................................................................................3-19
InvMatrix..........................................................................................................3-20
LinEv1D ...........................................................................................................3-21
LinEv2D ...........................................................................................................3-22
MatrixMul ........................................................................................................3-23
MaxMin1D .......................................................................................................3-24
MaxMin2D .......................................................................................................3-24
Mean.................................................................................................................3-25
Mul1D ..............................................................................................................3-26
Mul2D ..............................................................................................................3-27
Neg1D ..............................................................................................................3-28
Set1D................................................................................................................3-28
Sort ...................................................................................................................3-29
StdDev..............................................................................................................3-29
Sub1D...............................................................................................................3-30
Sub2D...............................................................................................................3-31
Subset1D ..........................................................................................................3-32
ToPolar .............................................................................................................3-32

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ToPolar1D ........................................................................................................3-33
ToRect ..............................................................................................................3-34
ToRect1D .........................................................................................................3-35
Transpose .........................................................................................................3-36
Error Conditions...........................................................................................................3-37

Chapter 4
GPIB/GPIB-488.2 Library ...........................................................................................4-1
GPIB Library Function Overview................................................................................4-1
GPIB Functions Library Function Panels ........................................................4-1
GPIB Library Concepts................................................................................................4-5
GPIB Libraries and the GPIB Dynamic Link Library/Device Driver..............4-5
Guidelines and Restrictions for Using the GPIB Libraries ..............................4-6
Device and Board Functions ............................................................................4-7
Automatic Serial Polling ..................................................................................4-7
Autopolling Compatibility ...................................................................4-8
Hardware Interrupts and Autopolling...............................................................4-8
Read and Write Termination ............................................................................4-9
Timeouts...........................................................................................................4-9
Global Variables for the GPIB Library ............................................................4-10
Different Levels of Functionality Depending on Platform and GPIB Board...4-10
Windows 95..........................................................................................4-10
Native 32-Bit Driver.................................................................4-10
Compatibility Driver ................................................................4-11
Windows NT ........................................................................................4-11
Limitations on Transfer Size ............................................................................4-11
Multithreading..................................................................................................4-11
Notification of SRQ and Other GPIB Events...................................................4-12
Synchronous Callbacks ........................................................................4-12
Asynchronous Callbacks ......................................................................4-12
Driver Version Requirements...............................................................4-12
GPIB Function Reference ............................................................................................4-13
CloseDev ..........................................................................................................4-13
CloseInstrDevs .................................................................................................4-14
ibInstallCallback...............................................................................................4-14
SRQI, RQS, and Auto Serial Polling ...................................................4-16
CallbackFunction .................................................................................4-17
ibNotify ............................................................................................................4-17
eventMask ............................................................................................4-18
SRQI, RQS, and Auto Serial Polling ...................................................4-19
CallbackFunction .................................................................................4-19
Restrictions on Operations in Asynchronous Callbacks ......................4-20
OpenDev...........................................................................................................4-21
ThreadIbcnt ......................................................................................................4-22
ThreadIbcntl .....................................................................................................4-22

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ThreadIberr.......................................................................................................4-23
ThreadIbsta.......................................................................................................4-25

Chapter 5
RS-232 Library .................................................................................................................5-1
RS-232 Library Function Overview.............................................................................5-1
The RS-232 Library Function Panels...............................................................5-1
Using RS-485 ...................................................................................................5-3
Reporting RS-232 Errors..................................................................................5-3
XModem File Transfer Functions ....................................................................5-3
Troubleshooting ...............................................................................................5-3
RS-232 Cable Information ...............................................................................5-4
Handshaking.....................................................................................................5-6
Software Handshaking .........................................................................5-6
Hardware Handshaking ........................................................................5-7
RS-232 Library Function Reference ............................................................................5-8
CloseCom .........................................................................................................5-8
ComBreak.........................................................................................................5-9
ComFromFile ...................................................................................................5-9
ComRd .............................................................................................................5-11
ComRdByte......................................................................................................5-12
ComRdTerm.....................................................................................................5-12
ComSetEscape..................................................................................................5-14
ComToFile .......................................................................................................5-15
ComWrt............................................................................................................5-16
ComWrtByte ....................................................................................................5-17
FlushInQ...........................................................................................................5-18
FlushOutQ ........................................................................................................5-19
GetComStat ......................................................................................................5-19
GetInQLen........................................................................................................5-20
GetOutQLen .....................................................................................................5-21
GetRS232ErrorString .......................................................................................5-22
InstallComCallback..........................................................................................5-22
OpenCom .........................................................................................................5-25
OpenComConfig ..............................................................................................5-26
ReturnRS232Err ...............................................................................................5-28
SetComTime ....................................................................................................5-29
SetCTSMode ....................................................................................................5-30
SetXMode.........................................................................................................5-31
XModemConfig ...............................................................................................5-31
XModemReceive..............................................................................................5-33
XModemSend...................................................................................................5-34
Error Conditions...........................................................................................................5-36

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Chapter 6
DDE Library ......................................................................................................................6-1
DDE Library Function Overview.................................................................................6-1
The DDE Library Function Panels...................................................................6-1
DDE Clients and Servers..................................................................................6-2
The DDE Callback Function ............................................................................6-2
DDE Links........................................................................................................6-4
A DDE Library Example Using Microsoft Excel and LabWindows/CVI.......6-5
DDE Library Function Reference ................................................................................6-6
AdviseDDEDataReady.....................................................................................6-6
BroadcastDDEDataReady ................................................................................6-8
ClientDDEExecute ...........................................................................................6-10
ClientDDERead................................................................................................6-10
ClientDDEWrite...............................................................................................6-12
ConnectToDDEServer .....................................................................................6-13
DisconnectFromDDEServer.............................................................................6-15
GetDDEErrorString..........................................................................................6-15
RegisterDDEServer..........................................................................................6-16
ServerDDEWrite ..............................................................................................6-19
SetUpDDEHotLink ..........................................................................................6-20
SetUpDDEWarmLink ......................................................................................6-21
TerminateDDELink..........................................................................................6-22
UnregisterDDEServer ......................................................................................6-23
Error Conditions...........................................................................................................6-23

Chapter 7
TCP Library .......................................................................................................................7-1
TCP Library Function Overview..................................................................................7-1
The TCP Library Function Panels....................................................................7-1
TCP Clients and Servers ..................................................................................7-2
The TCP Callback Function.............................................................................7-2
TCP Library Function Reference .................................................................................7-3
ClientTCPRead ................................................................................................7-3
ClientTCPWrite................................................................................................7-4
ConnectToTCPServer ......................................................................................7-5
DisconnectFromTCPServer .............................................................................7-7
DisconnectTCPClient.......................................................................................7-7
GetTCPErrorString...........................................................................................7-8
RegisterTCPServer...........................................................................................7-8
ServerTCPRead................................................................................................7-10
ServerTCPWrite ...............................................................................................7-11
UnregisterTCPServer .......................................................................................7-11
Error Conditions...........................................................................................................7-12

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Chapter 8
Utility Library ...................................................................................................................8-1
The Utility Library Function Panels.............................................................................8-1
Utility Library Function Reference ..............................................................................8-5
Beep..................................................................................................................8-5
Breakpoint ........................................................................................................8-6
CloseCVIRTE ..................................................................................................8-6
Cls ....................................................................................................................8-7
CopyFile ...........................................................................................................8-7
CVILowLevelSupportDriverLoaded................................................................8-8
DateStr..............................................................................................................8-9
Delay ................................................................................................................8-9
DeleteDir ..........................................................................................................8-10
DeleteFile .........................................................................................................8-10
DisableBreakOnLibraryErrors .........................................................................8-11
DisableInterrupts ..............................................................................................8-12
DisableTaskSwitching......................................................................................8-12
EnableBreakOnLibraryErrors ..........................................................................8-15
EnableInterrupts ...............................................................................................8-15
EnableTaskSwitching.......................................................................................8-16
ExecutableHasTerminated................................................................................8-16
GetBreakOnLibraryErrors................................................................................8-17
GetBreakOnProtectionErrors ...........................................................................8-18
GetCVIVersion.................................................................................................8-18
GetCurrentPlatform..........................................................................................8-19
GetDir...............................................................................................................8-20
GetDrive ...........................................................................................................8-20
GetExternalModuleAddr..................................................................................8-21
GetFileAttrs......................................................................................................8-23
GetFileDate ......................................................................................................8-24
GetFileSize .......................................................................................................8-25
GetFileTime .....................................................................................................8-26
GetFirstFile ......................................................................................................8-27
GetFullPathFromProject ..................................................................................8-29
GetInterruptState ..............................................................................................8-30
GetKey .............................................................................................................8-30
GetModuleDir ..................................................................................................8-31
GetNextFile ......................................................................................................8-33
GetPersistentVariable.......................................................................................8-33
GetProjectDir ...................................................................................................8-34
GetStdioPort .....................................................................................................8-35
GetStdioWindowOptions .................................................................................8-35
GetStdioWindowPosition.................................................................................8-36
GetStdioWindowSize .......................................................................................8-37
GetStdioWindowVisibility...............................................................................8-37

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GetSystemDate.................................................................................................8-38
GetSystemTime................................................................................................8-39
GetWindowDisplaySetting...............................................................................8-39
InitCVIRTE......................................................................................................8-40
inp.....................................................................................................................8-42
inpw..................................................................................................................8-42
InStandaloneExecutable ...................................................................................8-43
KeyHit ..............................................................................................................8-43
LaunchExecutable ............................................................................................8-44
LaunchExecutableEx........................................................................................8-47
LoadExternalModule........................................................................................8-49
LoadExternalModuleEx ...................................................................................8-52
MakeDir ...........................................................................................................8-54
MakePathname .................................................................................................8-55
outp...................................................................................................................8-56
outpw................................................................................................................8-56
ReadFromPhysicalMemory..............................................................................8-57
ReadFromPhysicalMemoryEx .........................................................................8-58
ReleaseExternalModule ...................................................................................8-59
RenameFile.......................................................................................................8-60
RetireExecutableHandle...................................................................................8-61
RoundRealToNearestInteger ............................................................................8-61
RunExternalModule .........................................................................................8-62
SetBreakOnLibraryErrors ................................................................................8-63
SetBreakOnProtectionErrors............................................................................8-64
SetDir ...............................................................................................................8-66
SetDrive............................................................................................................8-66
SetFileAttrs ......................................................................................................8-67
SetFileDate .......................................................................................................8-68
SetFileTime ......................................................................................................8-70
SetPersistentVariable .......................................................................................8-71
SetStdioPort......................................................................................................8-71
SetStdioWindowOptions..................................................................................8-72
SetStdioWindowPosition .................................................................................8-74
SetStdioWindowSize........................................................................................8-75
SetStdioWindowVisibility ...............................................................................8-76
SetSystemDate .................................................................................................8-76
SetSystemTime ................................................................................................8-77
SplitPath ...........................................................................................................8-77
SyncWait ..........................................................................................................8-79
SystemHelp ......................................................................................................8-79
TerminateExecutable........................................................................................8-82
Timer ................................................................................................................8-83
TimeStr.............................................................................................................8-83
TruncateRealNumber .......................................................................................8-84

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UnloadExternalModule ....................................................................................8-84
WriteToPhysicalMemory .................................................................................8-85
WriteToPhysicalMemoryEx.............................................................................8-86

Chapter 9
X Property Library .........................................................................................................9-1
X Property Library Overview.......................................................................................9-1
The X Property Library Function Panels .........................................................9-1
X Interclient Communication...........................................................................9-2
Property Handles and Types ............................................................................9-3
Communicating with Local Applications ........................................................9-3
The Hidden Window ........................................................................................9-3
Property Callback Functions ............................................................................9-4
Error Codes ......................................................................................................9-4
Using the Library Outside of LabWindows/CVI .............................................9-7
X Property Library Function Reference.......................................................................9-7
ConnectToXDisplay.........................................................................................9-7
CreateXProperty...............................................................................................9-9
CreateXPropType.............................................................................................9-10
DestroyXProperty.............................................................................................9-12
DestroyXPropType...........................................................................................9-13
DisconnectFromXDisplay................................................................................9-14
GetXPropErrorString .......................................................................................9-15
GetXPropertyName..........................................................................................9-15
GetXPropertyType ...........................................................................................9-16
GetXPropTypeName........................................................................................9-17
GetXPropTypeSize...........................................................................................9-18
GetXPropTypeUnit ..........................................................................................9-19
GetXWindowPropertyItem ..............................................................................9-20
GetXWindowPropertyValue ............................................................................9-22
InstallXPropertyCallback .................................................................................9-25
PutXWindowPropertyItem...............................................................................9-27
PutXWindowPropertyValue.............................................................................9-29
RemoveXWindowProperty ..............................................................................9-31
UninstallXPropertyCallback ............................................................................9-33

Chapter 10
Easy I/O for DAQ Library ...........................................................................................10-1
Easy I/O for DAQ Library Function Overview............................................................10-1
Advantages of Using the Easy I/O for DAQ Library.......................................10-1
Limitations of Using the Easy I/O for DAQ Library .......................................10-2
Easy I/O for DAQ Library Function Panels.....................................................10-2
Device Numbers...............................................................................................10-4
Channel String for Analog Input Functions .....................................................10-4
Command Strings.............................................................................................10-6

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Channel String for Analog Output Functions ..................................................10-7
Valid Counters for the Counter/Timer Functions ............................................10-7
Easy I/O for DAQ Function Reference ........................................................................10-8
AIAcquireTriggeredWaveforms ......................................................................10-8
AIAcquireWaveforms ......................................................................................10-13
AICheckAcquisition.........................................................................................10-15
AIClearAcquisition ..........................................................................................10-15
AIReadAcquisition...........................................................................................10-16
AISampleChannel ............................................................................................10-17
AISampleChannels...........................................................................................10-18
AIStartAcquisition ...........................................................................................10-19
AOClearWaveforms.........................................................................................10-20
AOGenerateWaveforms ...................................................................................10-21
AOUpdateChannel ...........................................................................................10-22
AOUpdateChannels..........................................................................................10-23
ContinuousPulseGenConfig.............................................................................10-24
CounterEventOrTimeConfig............................................................................10-26
CounterMeasureFrequency ..............................................................................10-29
CounterRead.....................................................................................................10-32
CounterStart .....................................................................................................10-33
CounterStop......................................................................................................10-34
DelayedPulseGenConfig ..................................................................................10-34
FrequencyDividerConfig..................................................................................10-37
GetAILimitsOfChannel....................................................................................10-40
GetChannelIndices ...........................................................................................10-41
GetChannelNameFromIndex ...........................................................................10-42
GetDAQErrorString .........................................................................................10-43
GetNumChannels .............................................................................................10-44
GroupByChannel..............................................................................................10-44
ICounterControl ...............................................................................................10-45
PlotLastAIWaveformsPopup ...........................................................................10-47
PulseWidthOrPeriodMeasConfig.....................................................................10-48
ReadFromDigitalLine.......................................................................................10-49
ReadFromDigitalPort .......................................................................................10-51
SetEasyIOMultitaskingMode ...........................................................................10-53
WriteToDigitalLine..........................................................................................10-53
WriteToDigitalPort...........................................................................................10-55
Error Conditions...........................................................................................................10-57

Appendix A
Customer Communication .............................................................................................A-1
Glossary ................................................................................................................................G-1
Index ......................................................................................................................................I-1

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Tables
Table 1-1. ANSI C Standard Library Classes .........................................................................1-1
Table 1-2. C Locale Information Values.................................................................................1-3
Table 2-1. The Formatting and I/O Library Function Tree.....................................................2-2
Table 3-1. The Analysis Library Function Tree......................................................................3-1
Table 3-2. Analysis Library Error Codes ................................................................................3-37
Table 4-1. The GPIB Functions Library Function Tree..........................................................4-2
Table 5-1.
Table 5-2.
Table 5-3.
Table 5-4.
Table 5-5.
Table 5-6.

The RS-232 Library Function Tree........................................................................5-1
PC Cable Configuration.........................................................................................5-4
DTE to DCE Cable Configuration.........................................................................5-5
PC to DTE Cable Configuration............................................................................5-5
Bit Definitions for the GetComStat Function ........................................................5-20
RS-232 Library Error Codes..................................................................................5-36

Table 6-1. DDE Library Function Tree...................................................................................6-1
Table 6-2. DDE Transaction Types (xType)...........................................................................6-4
Table 6-3. DDE Library Error Codes......................................................................................6-24
Table 7-1. The TCP Library Function Tree ............................................................................7-1
Table 7-2. TCP Transaction Types (xType)............................................................................7-3
Table 7-3. TCP Library Error Codes.......................................................................................7-12
Table 8-1. The Utility Library Function Tree .........................................................................8-1
Table 9-1.
Table 9-2.
Table 9-3.
Table 9-4.

The X Property Library Function Tree ..................................................................9-2
Predefined Property Types.....................................................................................9-3
X Property Library Error Types and Descriptions.................................................9-5
Status Values for InstallXPropertyCallback ..........................................................9-26

Table 10-1.
Table 10-2.
Table 10-3.
Table 10-4.
Table 10-5.

Easy I/O for DAQ Function Tree.........................................................................10-2
Valid Counters .....................................................................................................10-7
Definition of Am 9513: Counter +1 ....................................................................10-28
Adjacent Counters................................................................................................10-30
Easy I/O for DAQ Error Codes............................................................................10-57

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About This Manual
The LabWindows/CVI Standard Libraries Reference Manual contains information about the
LabWindows/CVI standard libraries—the Graphics Library, the Analysis Library, the Formatting
and I/O Library, the GPIB Library, the GPIB-488.2 Library, the RS-232 Library, the Utility
Library, and the system libraries. The LabWindows/CVI Standard Libraries Reference Manual
is intended for use by LabWindows/CVI users who have already completed the Getting Started
with LabWindows/CVI tutorial and are familiar with the LabWindows/CVI User Manual. To use
this manual effectively, you should be familiar with LabWindows/CVI and DOS fundamentals.

Organization of This Manual
The LabWindows/CVI Standard Libraries Reference Manual is organized as follows.
•

Chapter 1, ANSI C Library, describes the ANSI C Standard Library as implemented in
LabWindows/CVI.

•

Chapter 2, Formatting and I/O Library, describes the functions in the LabWindows/CVI
Formatting and I/O Library, and contains many examples of how to use them. The
Formatting and I/O Library contains functions that input and output data to files and
manipulate the format of data in a program.

•

Chapter 3, Analysis Library, describes the functions in the LabWindows/CVI Analysis
Library. The Analysis Library Function Overview section contains general information about
the Analysis Library functions and panels. The Analysis Library Function Reference section
contains an alphabetical list of the function descriptions.

•

Chapter 4, GPIB/GPIB-488.2 Library, describes the NI-488 and NI-488.2 functions in the
LabWindows/CVI GPIB Library, as well as the Device Manager functions in
LabWindows/CVI. The GPIB Library Function Overview section contains general
information about the GPIB Library functions and panels, the GPIB DLL, and guidelines
and restrictions you should know when using the GPIB Library. Detailed descriptions of the
NI-488 and NI-488.2 functions can be found in your NI-488.2 function reference manual.
The GPIB Function Reference section contains an alphabetical list of descriptions for the
Device Manager functions, the callback installation functions, and the functions for returning
the thread-specific status variables.

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About This Manual

•

Chapter 5, RS-232 Library, describes the functions in the LabWindows/CVI RS-232 Library.
The RS-232 Library Function Overview section contains general information about the RS-232
Library functions and panels. The RS-232 Library Function Reference section contains an
alphabetical list of function descriptions.

•

Chapter 6, DDE Library, describes the functions in the LabWindows/CVI DDE (Dynamic
Data Exchange) Library. The DDE Library Function Overview section contains general
information about the DDE Library functions and panels. The DDE Library Function
Reference section contains an alphabetical list of function descriptions. This library is
available for LabWindows/CVI for Microsoft Windows only.

•

Chapter 7, TCP Library, describes the functions in the LabWindows/CVI TCP (Transmission
Control Protocol) Library. The TCP Library Function Overview section contains general
information about the TCP Library functions and panels. The TCP Library Function
Reference section contains an alphabetical list of function descriptions.

•

Chapter 8, Utility Library, describes the functions in the LabWindows/CVI Utility Library.
The Utility Library contains functions that do not fit into any of the other LabWindows/CVI
libraries. The Utility Library Function Panels section contains general information about the
Utility Library functions and panels. The Utility Library Function Reference section contains
an alphabetical list of function descriptions.

•

Chapter 9, X Property Library, describes the functions in the Lab/Windows CVI X Property
Library. The X Property Library contains functions that read and write properties to and from
X Windows. The X Property Library Overview section contains general information about
the X Property Library functions and panels. The X Property Library Function Reference
section contains an alphabetical list of function descriptions.

•

Chapter 10, Easy I/O for DAQ Library describes the functions in the Easy I/O for DAQ
Library. The Easy I/O for DAQ Library Function Overview section contains general
information about the functions, and guidelines and restrictions you should know when using
the Easy I/O for DAQ Library. The Easy I/O for DAQ Library Function Reference section
contains an alphabetical list of function descriptions.

•

Appendix A, Customer Communication, contains forms you can use to request help from
National Instruments or to comment on our products and manuals.

•

The Glossary contains an alphabetical list and description of terms used in this manual,
including abbreviations, acronyms, metric prefixes, mnemonics, and symbols.

•

The Index contains an alphabetical list of key terms and topics in this manual, including the
page where you can find each one.

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Conventions Used in This Manual
The following conventions are used in this manual:
bold

Bold text denotes a parameter, menu item, return value, function
panel item, or dialog box button or option.

italic

Italic text denotes emphasis, a cross reference, or an introduction to
a key concept.

bold italic

Bold italic text denotes a note, caution, or warning.

monospace

Text in this font denotes text or characters that you should literally
enter from the keyboard. Sections of code, programming
examples, and syntax examples also appear in this font. This font
also is used for the proper names of disk drives, paths, directories,
programs, subprograms, subroutines, device names, variables,
filenames, and extensions, and for statements and comments taken
from program code.

italic monospace

Italic text in this font denotes that you must supply the appropriate
words or values in the place of these items.

<>

Angle brackets enclose the name of a key. A hyphen between two
or more key names enclosed in angle brackets denotes that you
should simultaneously press the named keys–for example,
.

»

The » symbol leads you through nested menu items and dialog
box options to a final action. The sequence
File » Page Setup » Options » Substitute Fonts
directs you to pull down the File menu, select the Page Setup
item, select Options, and finally select the Substitute Fonts
option from the last dialog box.

paths

Paths in this manual are denoted using backslashes (\) to
separate drive names, directories, and files, as in
drivename\dir1name\dir2name\myfile

IEEE 488, IEEE 488 and IEEE 488.2 refer to the ANSI/IEEE Standard 488.1-1987, IEEE 488.2
and the ANSI/IEEE Standard 488.2-1992, respectively, which define the GPIB.
Abbreviations, acronyms, metric prefixes, mnemonics, symbols, and terms are listed in the
Glossary.

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The LabWindows/CVI Documentation Set
For a detailed discussion of the best way to use the LabWindows/CVI documentation set, see the
section Using the LabWindows/CVI Documentation Set in Chapter 1, Introduction to
LabWindows/CVI of Getting Started with LabWindows/CVI.

Related Documentation
The following documents contain information that you may find helpful as you read this manual:
•

ANSI/IEEE Standard 488.1-1987, IEEE Standard Digital Interface for Programmable
Instrumentation

•

ANSI/IEEE Standard 488.2-1992, IEEE Standard Codes, Formats, Protocols, and Common
Commands

•

Harbison, Samuel P. and Guy L. Steele, Jr., C: A Reference Manual, Englewood Cliffs, NJ:
Prentice-Hall, Inc., 1995.

•

Nye, Adrian. Xlib Programming Manual. Sebastopol, California: O'Reilly & Associates,
1994. ISBN 0-937175-27-7

•

Gettys, James and Robert W. Scheifler. Xlib—C Language X Interface, MIT X Consortium
Standard. Cambridge, Massachussetts: X Consortium, 1994. ISBN (none)

Customer Communication
National Instruments wants to receive your comments on our products and manuals. We are
interested in the applications you develop with our products, and we want to help if you have
problems with them. To make it easy for you to contact us, this manual contains comment and
technical support forms for you to complete. These forms are in the appendix, Customer
Communication, at the end of this manual.

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Chapter 1
ANSI C Library
This chapter describes the ANSI C Standard Library as implemented in LabWindows/CVI.
Note: When you link your executable or DLL with an external compiler, you are using the
ANSI C library of the external compiler.
Table 1-1. ANSI C Standard Library Classes
Class
Character Handling
Character Testing
Character Case Mapping
Date and Time
Time Operations
Time Conversion
Time Formatting
Localization
Mathematics
Trigonometric Functions
Hyperbolic Functions
Exp and Log Functions
Power Functions
Nonlocal Jumping
Signal Handling
Input/Output
Open/Close
Read/Write/Flush
Line Input/Output
Character Input/Output
Formatted Input/Output
Buffer Control
File Positioning
File System Operations
Error Handling

Header File











(continues)

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Chapter 1

Table 1-1. ANSI C Standard Library Classes (Continued)
General Utilities
String to Arithmetic Expression
Random Number Generation
Memory Management
Searching and Sorting
Integer Arithmetic
Multibyte Character Sets
Program Termination
Environment
String Handling
Byte Operations
String Operations
String Searching
Collation Functions
Miscellaneous





Low-Level I/O Functions
Under UNIX you can use the low-level I/O functions (such as open, sopen, read, and
write) from the system library by including system header files in your program. Under
Windows you can use these functions by including cvi\include\ansi\lowlvlio.h in
your program. No function panels are provided for these functions.

Standard Language Additions
LabWindows/CVI does not support extended character sets that require more than 8 bits per
character. As a result, the wide character type wchar_t is identical to the single-byte char
type. LabWindows/CVI accepts wide character constants specified with the L prefix (as in
L‘ab’), but only the first character is significant. Furthermore, library functions that use the
wchar_t type operate only on 8-bit characters.
LabWindows/CVI supports variable argument functions using the ANSI C macros, with one
exception: none of the unspecified arguments can have a struct type. As a result, the macro
va_arg (ap, type) should never be used when type is a structure.
Note: LabWindows/CVI will not warn you about this error.
Under UNIX, LabWindows/CVI implements only the C locale as defined by the ANSI C
standard. The native locale, which is specified by the empty string, "", is also the C locale. The
following table shows the locale information values for the C locale.

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Table 1-2. C Locale Information Values
Name

Type

decimal_point

char *

"."

thousands_sep

char *

""

Non-monetary digit group separator character
or characters.

grouping

char *

""

Non-monetary digit groupings.

int_curr_symbol

char *

""

The three-character international currency
symbol, plus the character used to separate the
international symbol from the monetary
quantity.

currency_symbol

char *

""

The local currency symbol for the current
locale.

mon_decimal_point

char *

""

Decimal point character for monetary values.

mon_thousands_sep

char *

""

Monetary digit group separator character or
characters.

mon_grouping

char *

""

Monetary digit groupings.

positive_sign

char *

""

Sign character or characters for non-negative
monetary quantities.

negative_sign

char *

""

Sign character or characters for negative
monetary quantities.

int_frac_digits

char

CHAR_MAX

Digits appear to the right of the decimal point
for international monetary formats.

frac_digits

char

CHAR_MAX

Digits appear to the right of the decimal point
for other than international monetary formats.

p_cs_precedes

char

CHAR_MAX

1 if currency_symbol precedes nonnegative monetary values; 0 if it follows.

p_sep_by_space

char

CHAR_MAX

1 if currency_symbol is separated from
non-negative monetary values by a space;
else 0.

n_cs_precedes

char

CHAR_MAX

Like p_cs_precedes, for negative values.

n_sep_by_space

char

CHAR_MAX

Like p_sep_by_space, for negative
values.

p_sign_posn

char

CHAR_MAX

The positioning of positive_sign for a
non-negative monetary quantity, then its
currency_symbol.

n_sign_posn

char

CHAR_MAX

The positioning of negative_sign for a
negative monetary quantity, then its
currency_symbol.

© National Instruments Corporation

C locale Value Description
Decimal point character for non-monetary
values.

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Under Windows, LabWindows/CVI implements the default locale by using the appropriate items
from the Intl section of the WIN.INI file and appropriate Microsoft Windows functions.
Anything not mentioned here has the same behavior under the default locale as specified in the C
locale.
For the LC_NUMERIC locale:
• decimal_point maps to the value of sDecimal.
• thousands_sep maps to the value of sThousand.
For the LC_MONETARY locale:
• currency_symbol maps to the value of sCurrency.
• mon_decimal_point maps to the value of sDecimal.
• mon_thousands_sep maps to the value of sThousand.
• frac_digits maps to the value of iCurrDigits.
• int_frac_digits maps to the value of iCurrDigits.
• p_cs_precedes and n_cs_precedes are set to 1 if iCurrency equals 0 or 2,
otherwise they are set to 0.
• p_sep_by_space and n_sep_by_space are set to 0 if iCurrency equals 0 or 1,
otherwise they are set to 0.
• p_sign_posn and n_sign_posn are determined by the value of iNegCurr as follows:

Value of iNegCurr

Value of
p_sign_posn/n_sign_posn

0, 4

0

1, 5, 8, 9

1

3, 7, 10

2

6

3

2

4

For the LC_CTYPE locale:
• isalnum maps to the Windows function isCharAlphaNumeric.
• isalpha maps to the Windows function isCharAlpha.

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• islower maps to the Windows function isCharLower.
• isupper maps to the Windows function isCharUpper.
• tolower maps to the Windows function AnsiLower.
• toupper maps to the Windows function AnsiUpper.
For the LC_TIME locale:
• strftime uses the following items from the WIN.INI file for the appropriate format
specifiers: sTime, iTime, s1159, s2359, iTLZero, sShortDate, and sLongDate.
•

The names of the weekdays and the names of the months match the language version of
LabWindows/CVI. That is, a German version of LabWindows/CVI would use the German
names of months and days.

For the LC_COLLATE locale:
• strcoll maps to the Windows function lstrcmp.
Because LabWindows/CVI does not support extended character sets that require more than a
byte per character, a multibyte character in LabWindows/CVI is actually a single byte character.
Likewise, a multibyte sequence is a sequence of single byte characters. Because a multibyte
character is the same as a wide character, the conversion functions described in these sections do
little more than return their inputs as outputs.

Character Processing
LabWindows/CVI implements all the ANSI C character processing facilities as both macros and
functions. The macros are disabled when the LabWindows/CVI debugging level is set to
Standard or Extended, so that user protection is available for the arguments to the functions.

String Processing
Under UNIX, the strcoll function is equivalent to strcmp and its behavior is not affected by
the LC_COLLATE locale. Under Windows, strcoll is equivalent to the Windows function
lstrcmp. For both platforms, the function strxfrm performs a string copy using strncpy
and returns the length of its second argument.

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Input/Output Facilities
The function rename fails if the target file already exists. Under Microsoft Windows, rename
fails if the source and target files are on different disk drives. Under UNIX, rename fails if the
source and target files are on different file systems.
The functions fgetpos and ftell set errno to EFILPOS on error.

errno Set by File I/O Functions
The errno global variable is set to indicate specific error conditions by the ANSI C file I/O
functions and the low-level I/O functions. The possible values of errno are declared in
cvi\include\ansi\errno.h. There is a base set of values that is common to all
platforms. There are additional values that are specific to particular platforms.
Under Windows 3.1, errno gives very limited information. If the operating system returns an
error, errno is set to EIO.
Under Windows 95 and NT, you can call the Windows SDK GetLastError function to
obtain system specific information when errno is set to one of the following values:
EACCES
EBADF
EIO
ENOENT
ENOSPC

Mathematical Functions
The macro HUGE_VAL defined in the header math.h as well as the macros FLT_EPSILON,
FLT_MAX, FLT_MIN, DBL_EPSILON, DBL_MAX, DBL_MIN, LDBL_EPSILON, LDBL_MAX,
and DBL_MIN defined in the header float.h all refer to variables. Consequently, these
macros cannot be used in places where constant expressions are required, such as in global
initializations.

Time and Date Functions
Function time returns the number of seconds since January 1, 1990.
Functions mktime and localtime require time zone information to produce correct results.
LabWindows/CVI obtains time zone information from the environment variable named TZ, if it
exists. The value of this variable should have the format AAA[S]HH[:MM]BBB, where optional
items are in square brackets.

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The AAA and BBB fields specify the names of the standard and daylight savings time zones,
respectively (such as EST for Eastern Standard Time and EDT for Eastern Daylight Time). The
optional sign field S indicates whether the local time zone is to the west (+) or to the east (-) of
UTC (Greenwich Mean Time). The hour field (HH) and the optional minutes field (:MM) specify
the number of hours and minutes from UTC. As an example, the string EST05EDT specifies the
time zone information for the eastern part of the United States.
The functions gmtime, localtime, and mktime make corrections for daylight savings time
(DST). LabWindows/CVI uses a set of rules for determining when daylight savings time begins
and ends. A string in the messages file cvimsgs.txt in the LabWindows/CVI bin directory
specifies these rules. The following is the default value of this string.
":(1986)040102+0:110102-0:(1967)040102-0:110102-0"
This states that for the years from 1986 to the present, DST begins at 2:00 a.m. on the first
Sunday in April, and ends at 2:00 a.m. on the last Sunday in October. For the years from 1967 to
1985, DST begins at 2:00 a.m. on the last Sunday in March, and ends at 2:00 a.m. on the last
Sunday in October. You can change the way LabWindows/CVI determines DST by changing
this string in the cvimsgs.txt file. The countmsg.exe program must be executed after
changing the text file. You should execute the following line.
countmsg cvimsgs.txt

Control Functions
The assert macro defined by LabWindows/CVI does not print diagnostics to the standard
error stream when the debugging level is anything other than None. Instead, when the value of
its argument evaluates to zero, LabWindows/CVI will display a dialog box with a message
containing the file name, line number, and expression that caused the assert to fail.
Under UNIX, system passes the specified command to the Bourne shell (sh) as input, as if the
current process was performing a wait(2V) system call and was waiting until the shell
terminated. Callbacks are not called while the command is executing.
Under Windows, the executable can be either an MS DOS or Microsoft Windows executable,
including *.exe, *.com, *.bat, and *.pif files. The function does not return until the
command terminates, and user keyboard and mouse events are ignored until the command exits.
Callbacks for asynchronous events, such as idle events, Windows messages, and VXI interrupts,
PostDeferredCall calls, and DAQ events are called while the command is executing. If
you need to execute a command built into command.com such as copy, dir, and others, you
can call system with the command command.com /C DosCommand args, where
DosCommand is the shell command you would like executed. Refer to your DOS
documentation for further help with command.com. DOS executables (.exe, .com, and
.bat files) use the settings in _default.pif (in your Windows directory) when they are
running. You can change their priority, display options, and more by editing _default.pif

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Chapter 1

or by creating another .pif file. Refer to your Microsoft Windows documentation for help on
creating and editing .pif files.
If the function is passed a null pointer, LabWindows/CVI returns a non zero value if a command
processor is available. Under UNIX, if the argument is not a null pointer, the program returns a
zero. Under Microsoft Windows, if the argument is not a null pointer, the program returns zero
if the program was successfully started, otherwise it returns one of the following error codes.
-1
-3
-4
-6
-7
-9
-11
-12
-13
-14
-15
-16
-17
-20
-21
-22
-23
-24

System was out of memory, executable file was corrupt, or relocations were invalid.
File was not found.
Path was not found.
Attempt was made to dynamically link to a task, or there was a sharing or network
protection error.
Library required separate data segments for each task.
There was insufficient memory to start the application.
Windows version was incorrect.
Executable file was invalid. Either it was not a Windows application or there was an error
in the .EXE image.
Application was designed for a different operating system.
Application was designed for MS-DOS 4.0.
Type of executable file was unknown.
Attempt made to load a real-mode application (developed for an earlier Windows version.)
Attempt was made to load a second instance of an executable file containing multiple data
segments that were not marked read-only.
Attempt was made to load a compressed executable file. The file must be decompressed
before it can be loaded.
Dynamic-link library (DLL) file was invalid. One of the DLLs required to run this
application was corrupt.
Application requires Microsoft Windows 32-bit extensions.
Could not find toolhelp.dll or toolhelp.dll is corrupted.
Could not allocate a GetProcUserDefinedHandle.

The exit function does not actually flush and close the open streams. LabWindows/CVI leaves
files open so that they may be used from within the Interactive Window after execution of the
project terminates. The Close Libraries menu option under the Run menu performs this library
cleanup. This library cleanup is also performed when you restart execution of the project by
selecting Run Project from the Run menu. The argument passed to function exit is not used
by the LabWindows/CVI environment. Under UNIX, standalone executables created by
LabWindows/CVI return the value of the argument passed to the exit function.

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ANSI C Library

The UNIX version of LabWindows/CVI works with all the signals supported by UNIX in
addition to the ANSI C signals.

ANSI C Library Function Reference
For ANSI C function descriptions, consult a reference work such as C: A Reference Manual
which is listed in the Related Documentation section of About This Manual. Alternatively, you
can use LabWindows/CVI function panel help. The following function description is provided
because it is an extension of the ANSI C function set.

fdopen
FILE *fp = fdopen (int fileHandle, char *mode);
Note: This function is available only in the Windows version of LabWindows/CVI.
Purpose
You can use this function to obtain a pointer to a buffered I/O stream from a file handle returned
by one of the following functions.
(low-level I/O)
(low-level I/O)

open
sopen

You can use the return value just as if you had obtained it from fopen.
(Although this function is not in the ANSI standard, it is included in this library because it
returns a pointer to a buffered I/O stream.)
Parameters
Input

fileHandle

integer

File handle returned by open or sopen.

mode

string

Specifies the read/write, binary/text, and append modes.

Return Value
fp

FILE * Pointer to a buffered I/O file stream.

Return Codes
NULL (0)

Failure. More specific information is in errno.

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Parameter Discussion
mode is the same as the mode parameter to fopen.
You should use a mode value that is consistent with the mode in which you originally opened the
file. If you use write capabilities that were not enabled when the file handle was originally
opened, the call to fdopen succeeds, but any attempt to write fails. For instance, if you
originally opened the file for reading only, you can pass "rw" to fdopen, but any call to
fwrite fails.

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Chapter 2
Formatting and I/O Library
This chapter describes the functions in the LabWindows/CVI Formatting and I/O Library, and
contains many examples of how to use them. The Formatting and I/O Library contains functions
that input and output data to files and manipulate the format of data in a program.
The Formatting and I/O Library Function Overview section contains general information about
the Formatting and I/O Library functions and panels. Because the Formatting and I/O Library
differs in many respects from the other LabWindows/CVI libraries, it is very important to read
the overview before reading the other sections of this chapter.
The Formatting and I/O Library Function Reference section contains an alphabetical list of
function descriptions. This section is helpful for determining the syntax of the file I/O and string
manipulation functions.
The Using the Formatting and Scanning Functions section describes in detail this special class of
functions. Although these functions are listed in the function reference, their versatility and
complex nature require a more complete discussion.
The final section, Formatting and I/O Library Programming Examples, contains many examples
of program code that call Formatting and I/O Library functions. Most of the examples use the
formatting and scanning functions.

Formatting and I/O Library Function Overview
This section contains general information necessary for understanding the Formatting and I/O
Library functions and panels.

The Formatting and I/O Library Function Panels
The Formatting and I/O Library function panels are grouped in a tree structure according to the
types of operations performed. The Formatting and I/O Library function tree is shown in
Table 2-1.
The first- and second-level bold headings in the tree are the names of function classes and
subclasses. Function classes and subclasses are groups of related function panels. The
third-level headings in plain text are the names of individual function panels. The names of the
functions are in bold italics to the right of the function panels. Refer to the Sample Function
Panels for the Formatting and Scanning Functions section later in this chapter for more
information.

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Table 2-1. The Formatting and I/O Library Function Tree
Formatting and I/O
File I/O
Open File
Close File
Read from File
Write to File
Array to File
File to Array
Get File Information
Set File Pointer
String Manipulation
Get String Length
String to Lowercase
String to Uppercase
Fill Bytes
Copy Bytes
Copy String
Compare Bytes
Compare Strings
Find Pattern
Read Line
Write Line
Data Formatting
Formatting Functions
Fmt to Memory (Sample Panel)
Fmt to File
(Sample Panel)
Fmt to Stdout (Sample Panel)
Scanning Functions
Scan from Mem (Sample Panel)
Scan from File (Sample Panel)
Scan from Stdin (Sample Panel)
Status Functions
Get # Formatted Bytes
Get Format Index Error
Get I/O Error
Get I/O Error String

OpenFile
CloseFile
ReadFile
WriteFile
ArrayToFile
FileToArray
GetFileInfo
SetFilePtr
StringLength
StringLowerCase
StringUpperCase
FillBytes
CopyBytes
CopyString
CompareBytes
CompareStrings
FindPattern
ReadLine
WriteLine

Fmt
FmtFile
FmtOut
Scan
ScanFile
ScanIn
NumFmtdBytes
GetFmtErrNdx
GetFmtIOError
GetFmtIOErrorString

The classes and subclasses in the tree are described below:
•

The File I/O function panels open, close, read, write, and obtain information about files.

•

The String Manipulation function panels manipulate strings and character buffers.

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The Data Formatting function panels perform intricate formatting operations with a single
function call.
–

Formatting Functions, a subclass of Data Formatting, contains function panels that
combine and format one or more source items into a single target item.

–

Scanning Functions, a subclass of Data Formatting, contains function panels that
transform a single source item into several target items.

–

Status Functions, a subclass of Data formatting, contains function panels that return
information about the success or failure of a formatting or scanning call.

The online help with each panel contains specific information about operating each function
panel.

The String Manipulation Functions
The functions in the String Manipulation class perform common operations such as copying one
string to another, comparing two strings, or finding the occurrence of a string in a character
buffer. These functions are similar in purpose to the standard C string functions.

The Special Nature of the Formatting and Scanning Functions
The formatting and scanning functions are different in nature from the other functions in the
LabWindows/CVI libraries. With few exceptions, each LabWindows/CVI library function has a
fixed number of parameters, and each parameter has a definite data type. Each formatting and
scanning function, however, takes a variable number of parameters, and the parameters can be of
various data types. This difference is necessary to give the formatting and scanning functions
versatility.
For instance, a single Scan function call performs disparate operations, such as the following.
•

Find the two numeric values in the string:
"header: 45, -1.03e-2"

and place the first value in an integer variable and the second in a real variable.
•

Take the elements from an integer array, swap the high and low bytes in each element, and
place the resulting values in a real array.

To perform these operations, each formatting and scanning function takes a format string as one
of its parameters. In effect, a format string is a mini-program that instructs the formatting and
scanning functions on how to transform the input arguments to the output arguments. For
conciseness, format strings are constructed using single-character codes. These codes are

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described in detail in the Using the Formatting and Scanning Functions section later in this
chapter.
You may find the formatting and scanning functions more difficult to learn than other
LabWindows/CVI functions. To help you in this learning process, read the discussions in the
Formatting and I/O Library Programming Examples section at the end of this chapter.

Formatting and I/O Library Function Reference
This section gives a brief description of each of the functions available in the LabWindows/CVI
Formatting and I/O Library. The LabWindows/CVI Formatting and I/O Library functions are
arranged alphabetically.

ArrayToFile
int status = ArrayToFile (char *fileName, void *array, int dataType,
int numberOfElements, int numberOfGroups,
int arrayDataOrder, int fileLayout, int colSepStyle,
int fieldWidth, int fileType, int fileAction);
Purpose
Saves an array to a file using various formatting options. The function handles creating, opening,
writing, and closing the file. The file can later be read back into an array using the
FileToArray function.
Parameters
Input

fileName

string

File pathname.

array

void *

Numeric array.

dataType

integer

Array element data type.

numberOfElements

integer

Number of elements in array.

numberOfGroups

integer

Number of groups in array.

arrayDataOrder

integer

How groups are ordered in file.

fileLayout

integer

Direction to write groups in file.

colSepStyle

integer

How data on one line are separated.

fieldWidth

integer

Constant width between columns.

fileType

integer

ASCII/binary mode.

fileAction

integer

File pointer reposition location.

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Return Value
status

integer

Indicates success/failure.

Return Codes
0

Success.

-1

Error attempting to open file.

-2

Error attempting to close file.

-3

An I/O error occurred.

-4

Invalid dataType parameter.

-5

Invalid numberOfElements parameter.

-6

Invalid numberOfGroups parameter.

-7

Invalid arrayDataOrder parameter.

-8

Invalid fileLayout parameter.

-9

Invalid fileType parameter.

-10

Invalid separationStyle parameter.

-11

Invalid fieldWidth parameter.

-12

Invalid fileAction parameter.

Parameter Discussion
FileName may be an absolute pathname or a relative file name. If you use a relative file name,
the file is created relative to the current working directory.
DataType must be one of the following.
VAL_CHAR
VAL_SHORT_INTEGER
VAL_INTEGER
VAL_FLOAT
VAL_DOUBLE
VAL_UNSIGNED_SHORT_INTEGER
VAL_UNSIGNED_INTEGER
VAL_UNSIGNED_CHAR

If you save the array data in ASCII format, you may divide the array data into groups. Groups
can be written as either columns or rows. NumberOfGroups specifies the number of groups into
which to divide the array data. If you do not want to divide your data into groups, use 1.
If you divide your array data into groups, arrayDataOrder specifies how the data is ordered in
the array. The two choices are as follows.

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VAL_GROUPS_TOGETHER—all points of each data group are assumed to be stored consecutively

in the data array.
•

is assumed that the first point from each data group is stored
together, followed by the second point from each group and so on.
VAL_DATA_MULTIPLEXED—it

If you save the array data in ASCII format, fileLayout specifies how the data appears in the file.
The two choices are as follows.
•

VAL_GROUPS_AS_COLUMNS

•

VAL_GROUPS_AS_ROWS

If you have only one group, use VAL_GROUPS_AS_COLUMNS to write each array element on a
separate line.
If you specify that multiple values be written on each line, colSepStyle specifies how the values
are separated. The choices are as follows.
•

VAL_CONST_WIDTH—constant field width for each column

•

VAL_SEP_BY_COMMA—values followed by commas, except last value on line

•

VAL_SEP_BY_TAB—values separated by tabs

If you have specified a colSepStyle of VAL_CONST_WIDTH, fieldWidth specifies the width of
the columns.
FileType specifies whether to create the file in ASCII or binary format.
The choices are as follows.
•

VAL_ASCII

•

VAL_BINARY

FileAction specifies the location in the file to begin writing data if the named file already exists.
The choices are as follows.
•

VAL_TRUNCATE—Positions the file pointer to the beginning of the file and deletes its prior
contents.

•

VAL_APPEND—All write operations append data to file.

•

VAL_OPEN_AS_IS—Positions the file pointer at the beginning of the file but does not
affect the prior file contents.

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CloseFile
int status = CloseFile (int fileHandle);
Purpose
Closes the file associated with fileHandle. fileHandle is the file handle that was returned from
the OpenFile function and specifies the file to close.
Parameter
Input

fileHandle

integer

File handle.

integer

Result of the close file
operation.

Return Value
status

Return Codes
-1

Bad file handle.

0

Success.

CompareBytes
int result = CompareBytes (char *buffer#1, int buffer#1Index, char *buffer#2,
int buffer#2Index, int numberofBytes, int caseSensitive);
Purpose
Compares the numberofBytes starting at position buffer#1Index of buffer#1 to the
numberofBytes starting at position buffer#2Index of buffer#2.
Parameters
Input

buffer#1

string

String 1.

buffer#1Index

integer

Starting position in buffer#1.

buffer#2

string

String 2.

buffer#2Index

integer

Starting position in buffer#2.

numberofBytes

integer

Number of bytes to compare.

caseSensitive

integer

Case sensitivity mode.

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Return Value
integer

result

Result of the compare
operation.

Return Codes
-1

Bytes from buffer#1 less than bytes from buffer#2.

0

Bytes from buffer#1 identical to bytes from buffer#2.

1

Bytes from buffer#1 greater than bytes from
buffer#2.

Parameter Discussion
Both buffer#1Index and buffer#2Index are zero-based.
If caseSensitive is zero, alphabetic characters are compared without regard to case. If
caseSensitive is non-zero, alphabetic characters are considered equal only if they have the same
case.
The function returns an integer value indicating the lexicographic relationship between the two
sets of bytes.

CompareStrings
int result = CompareStrings (char *string#1, int string#1Index, char *string#2,
int string#2Index, int caseSensitive);
Purpose
Compares the NUL-terminated string starting at position string#1Index of string#1 to the
NUL-terminated string starting at position string#2Index of string#2. Both string#1Index and
string#2Index are zero-based.
Parameters
Input

string#1

string

String 1.

string#1Index

integer

Starting position in string#1.

string#2

string

String 2.

string#2Index

integer

Starting position in string#2.

caseSensitive

integer

Case sensitivity mode.

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Return Value
integer

result

Result of the compare
operation.

Return Codes
-1

Bytes from string#1 less than bytes from string#2.

0

Bytes from string#1 identical to bytes from string#2.

1

Bytes from string#1 greater than bytes from string#2.

Parameter Discussion
If caseSensitive is zero, alphabetic characters are compared without regard to case. If
caseSensitive is non-zero, alphabetic characters are equal only if they have the same case.
The function returns an integer value indicating the lexicographic relationship between the two
strings.

CopyBytes
void CopyBytes (char targetBuffer[], int targetIndex, char *sourceBuffer,
int sourceIndex, int numberofBytes);
Purpose
Copies the numberofBytes bytes starting at position sourceIndex of sourceBuffer to position
targetIndex of targetBuffer.
Parameters
Input

Output

targetIndex

integer

Starting position in
targetBuffer.

sourceBuffer

string

Source buffer.

sourceIndex

integer

Starting position in
sourceBuffer.

numberofBytes

integer

Number of bytes to copy.

targetBuffer

string

Destination buffer.

Return Value
None
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Parameter Discussion
Both sourceIndex and targetIndex are zero-based.
You can use this function even when sourceBuffer and targetBuffer overlap.

CopyString
void CopyString (char targetString[], int targetIndex, char *sourceString,
int sourceIndex, int maximum#Bytes);
Purpose
Copies the string starting at position sourceIndex of sourceString to position targetIndex of
targetString until an ASCII NUL is copied or maximum#Bytes bytes have been copied.
Appends an ASCII NUL if no ASCII NUL was copied.
Parameters
Input

targetIndex

integer

Starting position in targetString.

sourceString

string

Source buffer.

sourceIndex

integer

Starting position in sourceString.

maximum#Bytes integer
Output

targetString

string

Number of bytes to copy, excluding the ASCII
NUL.
Destination buffer.

Return Value
None
Parameter Discussion
Both sourceIndex and targetIndex are zero-based. If you want to use maximum#Bytes to
prevent from writing beyond the end of targetString, make sure that you allow room for the
ASCII NUL. For example, if maximum#Bytes is 40, the destination buffer should contain at
least 41 bytes.
If you do not want to specify a maximum number of bytes to copy, use -1 for maximum#Bytes.
You can use this function even when sourceString and targetString overlap.
Note: The value of maximum#Bytes must not exceed one less than the number of bytes in
the target variable.

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FileToArray
int status = FileToArray (char *fileName, void *array, int dataType,
int numberOfElements, int numberOfGroups,
int arrayDataOrder, int fileLayout, int fileType);
Purpose
Reads data from a file into an array. Can be used with files created using the ArrayToFile
function. The function handles creating, opening, reading, and closing the file.
Parameters
Input

Output

fileName

string

File pathname.

dataType

integer

Array element data type.

numberOfElements

integer

Number of elements in array.

numberOfGroups

integer

Number of Groups in array.

arrayDataOrder

integer

How groups are ordered in file.

fileLayout

integer

Direction to write groups in file.

fileType

integer

ASCII/binary mode.

array

void*

Numeric array.

integer

Indicates success or failure.

Return Value
status
Return Code
0

Success.

-1

Error attempting to open file.

-2

Error attempting to close file.

-3

An I/O error occurred.

-4

Invalid arrayDataType parameter.

-5

Invalid numberOfElements parameter.

-6

Invalid numberOfGroups parameter.

-7

Invalid arrayDataOrder parameter.

-8

Invalid fileLayout parameter.

-9

Invalid fileType parameter.

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Parameter Discussion
FileName may be an absolute pathname or a relative file name. If you use a relative file name,
the file is located relative to the current working directory.
DataType must be one of the following.
• VAL_CHAR
• VAL_SHORT_INTEGER
• VAL_INTEGER
• VAL_FLOAT
• VAL_DOUBLE
• VAL_UNSIGNED_SHORT_INTEGER
• VAL_UNSIGNED_INTEGER
• VAL_UNSIGNED_CHAR
NumberOfGroups specifies the number of groups into which the data in the file is divided.
Groups can be in the form of either columns or rows. If there are no groups, use 1. This
parameter only applies if the file type is ASCII.
If the data is divided into groups, arrayDataOrder specifies the order in which the data is to be
stored in the array. The two choices are as follows.
•

VAL_GROUPS_TOGETHER— all points from one data group are stored together followed by
all points from the next data group.

•

VAL_DATA_MULTIPLEXED—the first points from each data group are stored
consecutively, followed by the second points from each group, etc.

If the file is in ASCII format, fileLayout specifies how the data appears in the file. The two
choices are as follows.
• VAL_GROUPS_AS_COLUMNS
• VAL_GROUPS_AS_ROWS
If there is only one group, VAL_GROUPS_AS_COLUMNS specifies that each value in the file is
on a separate line.
FileType specifies whether the file is in ASCII or binary format. The choices are as follows.
• VAL_ASCII
• VAL_BINARY

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FillBytes
void FillBytes (char buffer[], int startingIndex, int numberofBytes, int value);
Purpose
Sets the numberofBytes bytes starting at position startingIndex of buffer to the value in the
lower byte of value. startingIndex is zero-based.
Parameters
Input

buffer

string

Destination buffer.

startingIndex

integer

Starting position in buffer.

numberofBytes

integer

Number of bytes to fill.

value

integer

Value to place in bytes.

Return Value
None

FindPattern
int ndx = FindPattern (char *buffer, int startingIndex, int numberofBytes,
char *pattern, int caseSensitive, int startFromRight);
Purpose
Searches a character buffer for a pattern of bytes. The pattern of bytes is specified by the string
pattern.
Parameters
Input

buffer

string

Buffer to be searched.

startingIndex

integer

Starting position in buffer.

numberofBytes

integer

Number of bytes to search.

pattern

string

Pattern to search for.

caseSensitive

integer

Case-sensitivity mode.

startFromRight

integer

Direction of search.

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Return Value
ndx

integer

Index in buffer where pattern
was found.

Return Code
-1

Pattern not found.

Parameter Discussion
The buffer searched is the set of numberofBytes bytes starting at position startingIndex of
buffer. Exception: If numberofBytes is -1, the buffer searched is the set of bytes starting at
position startingIndex of buffer up to the first ASCII NUL. startingIndex is zero-based.
If caseSensitive is zero, alphabetic characters are compared without regard to case. If
caseSensitive is non-zero, alphabetic characters are considered equal only if they have the same
case. If startFromRight is zero, the leftmost occurrence of the pattern in the buffer will be
found. If startFromRight is non-zero, the rightmost occurrence of the pattern in the buffer will
be found.
If the pattern is found, pattern returns the index relative to the beginning of buffer where it
found the first byte of the pattern. If the pattern is not found, pattern returns -1.
The following example returns 4, which is the index of the second of the three occurrences of ab
in the string 1ab2ab3ab4. The first occurrence is skipped because startingIndex is 3. Of the
two remaining occurrences, the leftmost is found because startFromRight is zero:
ndx = FindPattern ("1ab2ab3ab4", 3, -1, "AB", 0, 0);

On the other hand, the following line returns 7, which is the index of the last occurrence of ab,
because startFromRight is non-zero:
ndx = FindPattern ("1ab2ab3ab4", 3, -1, "AB", 0, 1);

Fmt
int n = Fmt (void *target, char *formatString, source1,...,sourcen);
Purpose
Formats the source1 ... sourcen arguments according to descriptions in the formatString
argument.

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Parameters
Input

formatString

String.

source1,…,sourcen Types must match formatString contents.
Output

target

Type must match formatString contents.

Return Value
integer

n

Number of source format
specifiers satisfied.

Return Code
-1

Format string error.

Using This Function
This function places the result of the formatting into the target argument, which you must pass by
reference. The return value indicates how many source format specifiers were satisfied, or
-1 if the format string is in error. A complete discussion of this function is in the Using the
Formatting and Scanning Functions section later in this chapter.

FmtFile
int n = FmtFile (int fileHandle, char *formatString, source1,…,sourcen);
Purpose
Formats the source1 ... sourcen arguments according to descriptions in the formatString
argument. The result of the formatting is written into the file corresponding to the fileHandle
argument, which was obtained by a call to the LabWindows/CVI function OpenFile.
Parameters
Input

fileHandle

integer

formatString

string

source1,…,sourcen

types must match formatString
contents

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Return Value
integer

n

Number of source format
specifiers satisfied.

Return Codes
-1

Format string error

-2

I/O error.

Using This Function
The return value indicates how many source format specifiers were satisfied, -1 if the format
string is in error, or -2 if there was an I/O error. A complete discussion of this function is in the
Using the Formatting and Scanning Functions section later in this chapter.

FmtOut
int n = FmtOut (char *formatString, source1,…,sourcen);
Purpose
Formats the source1 ... sourcen arguments according to descriptions in the formatString
argument. The result of the formatting is written to the Standard I/O window.
Parameters
Input

formatString

String.

source1,…,sourcen Types must match formatString contents.
Return Value
n

integer

Number of source format
specifiers satisfied.

Return Codes
-1

Format string error.

-2

I/O error.

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Using This Function
The return value indicates how many source format specifiers were satisfied, -1 if the format
string is in error, or -2 if there was an I/O error. A complete discussion of this function is in the
Using the Formatting and Scanning Functions section later in this chapter.

GetFileInfo
int status = GetFileInfo (char *fileName, long *fileSize);
Purpose
Verifies if a file exists. Returns an integer value of zero if no file is present and 1 if file is
present. fileSize is a long variable that contains the file size in bytes or zero if no file exists.
Parameters
Input

fileName

string

Pathname of the file to be
checked.

Output

fileSize

long

File size or zero.

integer

Indicates if the file exists.

Return Value
status
Return Codes
1

File exists.

0

File does not exist.

-1

Maximum number of files already open.

Example
/*
Check for presence of file A:\DATA\TEST1.DAT. */
/*
Print its size */
/*
if file exists or message stating file does not exist. */
int n;
long size;
n = GetFileInfo("a:\\data\\test1.dat",&size);
if (n == 0)
FmtOut("File does not exist.");
else
FmtOut("File size = %i[b4]",size);

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GetFmtErrNdx
int n = GetFmtErrNdx (void);
Purpose
Returns the zero-based index into the format string where an error occurred in the last formatting
or scanning call.
Parameters
None
Return Value
integer

n

Position of error in format
string.

Return Code
-1

No error.

Using This Function
If the format string of the preceding call contains an error, such as an invalid format, or
inappropriate modifier, the return value indicates the position within the format string, beginning
with position zero, where the error was found. The function can report only one error per call,
even if several errors existed within the string.
Example
int i, n;
Scan ("1234", "%s>%d", &i);
n = GetFmtErrNdx ();
/* n will have the value -1, indicating that */
/* there was no error found in the format string. */

GetFmtIOError
int status = GetFmtIOError (void);
Purpose
This function returns specific I/O information for the last call to a Formatting and I/O function
that performs file I/O. If the last function was successful, GetLastFmtIOError returns zero (no

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error). If the last function that performs I/O encountered an I/O error, GetLastFmtIOError
returns a nonzero value.
Return Value
status

integer

Indicates success or failure of last function that
performed file I/O.

Return Codes
FmtIONoErr

0

No error.

FmtIONoFileErr

1

File not found.

FmtIOGenErr

2

General I/O error.

FmtIOBadHandleErr

3

Invalid file handle.

FmtIOInsuffMemErr

4

Not enough memory.

FmtIOFileExistsErr

5

File already exists.

FmtIOAccessErr

6

Permission denied.

FmtIOInvalArgErr

7

Invalid argument.

FmtIOMaxFilesErr

8

Maximum number of files open.

FmtIODiskFullErr

9

Disk is full.

FmtIONameTooLongErr 10

File name is too long.

GetFmtIOErrorString
char *message = GetFmtIOErrorString (int errorNum);
Purpose
Converts the error number returned by GetLastFmtIOError into a meaningful error message.
Parameters
Input errorNum

integer

Error Code returned by GetLastFmtIOErr.

string

Explanation of error.

Return Value
message

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NumFmtdBytes
int n = NumFmtdBytes (void);
Purpose
Returns the number of bytes formatted or scanned by the previous formatting or scanning call.
Parameters
None
Return Value
integer

n

Number of bytes formatted or
scanned.

Using This Function
If the previous call was a formatting call, NumFmtdBytes returns the number of bytes placed into
the target. If the previous call was a scanning call, NumFmtdBytes returns the number of bytes
scanned from the source. The return value is undefined if there have been no preceding formatting
or scanning calls.
Certain operations using the FmtFile and ScanFile routines can result in more than 64 KB
being formatted or scanned. Because NumFmtdBytes returns an integer, its value will not be
accurate in these cases. The value returned rolls over when formatting or scanning more than
65,535 bytes.
Example
double f;
int n;
Scan ("3.1416", "%s>%f", &f);
n = NumFmtdBytes ();
/* n will have the value 6, indicating that six bytes */
/* were scanned from the source string. */

OpenFile
int handle = OpenFile (char *fileName, int read/writeMode, int action, int fileType);
Purpose
Opens a file for input and/or output.

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Parameters
Input

fileName

string

Pathname.

read/writeMode

integer

Read/write mode.

action

integer

File pointer reposition location.

fileType

integer

ASCII/binary mode.

integer

File handle to be used in
subsequent ReadFile/WriteFile
calls.

Return Value
handle

Return Code
-1

Function failed, unable to open file, or bad argument
to function.

Parameter Discussion
fileName is a pathname specifying the file to be opened. If the read/writeMode argument is
write or read/write, this function creates the file if it does not already exist. If a file is created, it
is created with no protection; that is, both reading and writing can be performed on it. Use the
function GetFileInfo if it is necessary to determine whether a file already exists.
read/writeMode specifies how the file is opened:
•

VAL_READ_WRITE = open file for reading and writing

•

VAL_READ_ONLY = open file for reading only

•

VAL_WRITE_ONLY = open file for writing only

action specifies whether to delete the old contents of the file, and whether to force the file
pointer to the end of the file before each write operation. action is meaningful only if
read/writeMode = write or read/write. After read operations are performed, the file pointer
points to the byte following the last byte read. action values are as follows:
•

VAL_TRUNCATE = truncate file (deletes its old contents and positions the file pointer at the
beginning of the file.

•

VAL_APPEND = do not truncate file (all write operations append to end of file).

•

VAL_OPEN_AS_IS = do not truncate file (positions the file pointer at the beginning of the
file. )

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fileType specifies whether to treat file as ASCII or binary. When performing I/O on a file in
binary mode, no special treatment is given to carriage returns (CR) and line feeds (LF). When
you open the file in ASCII mode, CR LF combination translates to LF when reading, and LF
translates to CR LF when writing. fileType values are as follows:
•

VAL_BINARY = binary

•

VAL_ASCII = ASCII

ReadFile
int n = ReadFile (int fileHandle, char buffer[], int count);
Purpose
Reads up to count bytes of data from a file or STDIN into buffer. Reading starts at the current
position of the file pointer. When the function completes, the file pointer points to the next
unread character in the file.
Parameters
Input
Output

fileHandle

integer

File handle.

count

integer

Number of bytes to read.

buffer

string

Input buffer.

integer

Number of bytes read.

Return Value
n
Return Codes
-1
0

Error, possibly bad handle.
Tried to read past end-of-file.

Parameter Discussion
fileHandle is the file handle returned by the OpenFile function. fileHandle points to the file
from which you want to read. If fileHandle =0, input is read from STDIN, and no prior
OpenFile call is needed. buffer is the buffer into which you read data. You must allocate
space for this buffer before you call this function. count specifies the number of bytes to read.
count must not be greater than buffer size.

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Using This Function
The return value can be less than number of bytes requested if end of file was reached before
byte count was satisfied. Notice that if you open the file in ASCII mode, each CR LF
combination read is counted as 1 character, because the pair is translated into LF when stored in
the buffer.
Note: This function does not terminate the buffer with an ASCII NUL.

ReadLine
int n = ReadLine (int fileHandle, char lineBuffer[], int maximum#Bytes);
Purpose
Reads bytes from a file until a linefeed is encountered.
Parameters
Input

Output

fileHandle

integer

File handle.

maximum#Bytes

integer

Maximum number of bytes to
read into line, excluding the
ASCII NUL.

lineBuffer

string

Input buffer.

integer

Number of bytes read,
excluding linefeed.

Return Value
n

Return Codes
-2

End of file.

-1

I/O error.

Parameter Discussion
This function places up to maximum#Bytes bytes, excluding the linefeed, into lineBuffer.
Appends an ASCII NUL to lineBuffer. If there are more than maximum#Bytes bytes before the
linefeed, the extra bytes are discarded.
fileHandle is the file handle that was returned from the OpenFile function and specifies the
file from which to read the line. The file should be opened in ASCII mode so that a

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carriage-return/linefeed combination will be treated as a linefeed. If fileHandle is zero, the line
will be read from the standard input.
lineBuffer is a character buffer. It should be large enough to contain maximum#Bytes bytes
plus an ASCII NUL.
ReadLine returns the number of bytes read from the file, including discarded bytes, but
excluding the linefeed. Hence, the return value will exceed maximum#Bytes if and only if bytes
are discarded.
If no bytes are read because the end of the file has been reached, ReadLine returns -2. If an
I/O error occurs, ReadLine returns -1.

Scan
int n = Scan (void *source, char *formatString, targetptr1,…,targetptrn);
Purpose
Scans a single source item in memory and breaks it into component parts according to format
specifiers found in a formatString. The components are then placed into the target parameters.
Parameters
Input
Output

source

Type must match formatString contents

formatString

string.

targetptr1,…,targetptrn

Types must match formatString contents.

Return Value
n

integer

Number of target format
specifiers satisfied.

Return Code
-1

Format string error.

Using This Function
The return value indicates how many target format specifiers were satisfied, or -1 if the format
string is in error. A complete discussion of this function is in the Using the Formatting and
Scanning Functions section later in this chapter.

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ScanFile
int n = ScanFile (int fileHandle, char *formatString, targetptr1,…,targetptrn);
Purpose
Performs the same basic operation as the Scan function, except that the source material is
obtained from the file referred to by the fileHandle argument, which is obtained by calling the
LabWindows/CVI function OpenFile.
Parameters
Input
Output

fileHandle

Integer.

formatString

String.

targetptr1,…,targetptrn

Types must match formatString contents.

Return Value
n

integer

Number of target format
specifiers satisfied.

Return Codes
-1

Format string error.

-2

I/O error.

Using This Function
The amount of data read from the file depends on the amount needed to fulfill the formats in the
format string. The return value indicates how many target format specifiers were satisfied, -1 if
the format string is in error, or -2 if there was an I/O error. A complete discussion of this
function is in the Using the Formatting and Scanning Functions section later in this chapter.

ScanIn
int n = ScanIn (char *formatString, targetptr1,…,targetptrn);
Purpose
Performs the same basic operation as the ScanFile function, except that the source material is
obtained from STDIN.

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Parameters
Input

formatString

String.

Output

targetptr1,…,targetptrn

Types must match formatString contents.

Return Value
integer

n

Number of target format
specifiers satisfied.

Return Codes
-1

Format string error.

-2

I/O error.

Using This Function
No argument is required for the source item in the case of the ScanIn function. The return
value indicates how many target format specifiers were satisfied, -1 if the format string is in
error, or -2 if there was an I/O error. A complete discussion of this function is in the Using the
Formatting and Scanning Functions section later in this chapter.

SetFilePtr
long position = SetFilePtr (int fileHandle, long offset, int origin);
Purpose
Moves the file pointer for the file specified by fileHandle to a location that is offset bytes from
origin. Returns the offset of the new file pointer position from the beginning of the file.
Parameters
Input

fileHandle

integer

File handle returned by
OpenFile.

offset

long integer

Number of bytes from origin to
position of file pointer.

origin

integer

Position in file from which to
base offset.

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Return Value
position

long integer

Offset of the new file pointer
position from the beginning of
the file.

Return Code
-1

Error due to an invalid file handle, an invalid origin
value, or an offset value that is before the beginning
of the file.

Parameter Discussion
The valid values of origin are as follows:
•

0 = beginning of file

•

1 = current position of file pointer

•

2 = end of file

Using This Function
This function can also be used to obtain the file size by setting offset to 0 and origin to 2. In this
case, the return value indicates the file size and the pointer will be at the end of the file.
It is possible to position the file pointer beyond the end of the file. Intermediate bytes (bytes
between the old end of file and the new end of file) contain indeterminate values. An attempt to
position the file pointer before the beginning of the file causes the function to return an error.
If the file is a device that does not support random access (such as the standard input), the
function returns an indeterminate value.
Example
/* Open or create the file c:\TEST.DAT, move 10 bytes into the
file, and write a string to the file. */
/* Note: Use \\ in pathname in C instead of \. */
int handle,result;
long position;
handle = OpenFile("c:\\TEST.DAT", 0, 2, 1);
if (handle == -1){
FmtOut("error opening file");
exit(1);
}
position = SetFilePtr(handle, 10L, 0);
if (position == 10){

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result = WriteFile(handle, "Hello, World!", 13);
if (result == -1)
FmtOut("error writing to file");
}
else
FmtOut("error positioning file pointer");
CloseFile(handle);

StringLength
int n = StringLength (char *string);
Purpose
Returns the number of bytes in the string before the first ASCII NUL.
Parameter
Input

string

String.

Return Value
integer

n

Number of bytes in string
before ASCII NUL.

Example
char s[100];
int nbytes;
nbytes = StringLength (s);

StringLowerCase
void StringLowerCase (char string[]);
Purpose
Converts all uppercase alphabetic characters in the NUL-terminated string to lowercase.
Parameter
Input/Output string

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Return Value
None

StringUpperCase
void StringUpperCase (char string[]);
Purpose
Converts all lowercase alphabetic characters in the NUL-terminated string to uppercase.
Parameter
Input/Output string

String.

Return Value
None

WriteFile
int n = WriteFile (int fileHandle, char *buffer, unsigned int count);
Purpose
Writes up to count bytes of data from buffer to a file or to STDOUT. Writing starts at the
current position of the file pointer, and when the function completes, the file pointer is
incremented by the number of bytes written.
Parameters
Input

fileHandle

integer

File handle.

buffer

string

Data buffer.

count

integer

Number of bytes to write.

integer

Number of bytes written to the
file.

Return Value
n

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Return Code
-1

Error.

Parameter Discussion
fileHandle is the file handle that was returned from the OpenFile function. If fileHandle=1,
data is written to STDOUT and no prior OpenFile call is needed.
buffer is the buffer from which to write data.
count specifies number of bytes to write. The count parameter overrides the buffer size in
determining the number of bytes to write. Buffers containing embedded NUL bytes are written in
full. count must not be greater than buffer size.
Using This Function
For files opened in ASCII mode, each LF character is replaced with a CR-LF combination in the
output. In this case, the return value does not include the CR character written to the output.
An error can indicate a bad file handle, an attempt to access a protected file, an attempt to write
to a file opened as ReadOnly, or no more space left on disk.

WriteLine
int n = WriteLine (int fileHandle, char *lineBuffer, int numberofBytes);
Purpose
Writes numberofBytes bytes from lineBuffer to a file and then writes a linefeed to the file.
Parameters
Input

fileHandle

integer

File handle.

lineBuffer

string

Data buffer.

numberofBytes

integer

Number of bytes to write.

integer

Number of bytes written.
including line feed.

Return Value
n

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Return Code
-1

I/O error.

Parameter Discussion
If numberofBytes is -1, only the bytes in lineBuffer before the first ASCII NUL are written,
followed by a linefeed.
fileHandle is the file handle that was returned from the OpenFile function. The file should be
opened in ASCII mode so that a carriage return will be written before the linefeed. If fileHandle
is 1, the line will be written to the STDOUT.
Using This Function
WriteLine returns the number of bytes written to the file, excluding the linefeed. If an I/O
error occurs, WriteLine returns -1.

Using the Formatting and Scanning Functions
You use data formatting functions to translate or reformat data items into other forms. Typical
usages might be to translate between data stored on external files and the internal forms which
the program can manipulate, or to reformat a foreign binary representation into one on which the
program can operate.
There are three subclasses of data formatting functions in the LabWindows/CVI Formatting and
I/O Library:
•

Formatting functions

•

Scanning functions

•

Status functions

You use formatting functions to combine and format one or more source items into a single
target item, and you use scanning functions to break apart a single source item into several target
items. The status functions return information regarding the success or failure of the formatting
or scanning functions.

Introductory Formatting and Scanning Examples
To introduce you to the formatting and scanning functions, consider the following examples.

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Convert the integer value 23 to its ASCII representation and place the contents in a string
variable:
char a[5];
int b,n;
b = 23;
n = Fmt (a, "%s<%i", b);

After the Fmt call, a contains the string 23.
In this example, a is the target argument, b is the source argument, and the string %s<%i is the
format string. The Fmt call uses the format string to determine how to convert the source
argument into the target argument.
With the Scan function, you can convert the string 23 to an integer:
char *a;
a = "23";
n = Scan (a$, "%s>%i", b%);

After the Scan call, b = 23.
In this example, a is the source argument, b is the target argument, and %s>%i is the format
string. In both the formatting and the scanning functions, the format string defines the variable
types of the source and target arguments and the method by which the source arguments are
transformed into the target arguments.

Formatting Functions
The following information is a brief description of the three formatting functions:
•

n = Fmt (target, formatstring, source1, ..., sourcen);

The Fmt function formats the source1, ..., sourcen arguments according to
descriptions in the formatstring argument. The function places the result of the
formatting into the target argument.
•

n = FmtFile (handle, formatstring, source1, ..., sourcen);

The FmtFile function formats the source1, ..., sourcen arguments according to
descriptions in the formatstring argument. The function writes the result of the
formatting into the file corresponding to the handle argument.
•

n = FmtOut (formatstring, source1, ..., sourcen);

The FmtOut function formats the source1, ..., sourcen arguments according to
descriptions in the formatstring argument. The function writes the result of the
formatting to Standard Out.

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Each of these formatting functions return the number of source format specifiers satisfied. If
there is an error in the format string, -1 is returned.
The formatting functions are used to format and combine multiple source items into a single
target item. The only difference in the workings of the three functions is the location of the
target data. For the function Fmt, the target is a data item in memory which is passed to the
function by reference. For FmtFile, the target is a file whose handle is passed as the first
argument. The LabWindows/CVI function OpenFile returns this handle. For the function
FmtOut, the target is Standard Out (typically the display), and in this case the target argument
present in the other two functions is omitted. Except for these differences, the following
descriptions apply to all the formatting functions.
The target parameter for Fmt must be passed by reference (that is, must be a pointer).
Formatting Functions—Format String
Consider the following formatting function:
n = Fmt(target, formatstring, source1, ..., sourcen);

where formatstring contains the information to transform the source arguments to the target
argument.
Format strings for all the formatting functions are of the form:
"target_spec < source_specs_and_literals"

where target_spec is a format specifier that describes the nature of the target data item, and
source_specs_and_literals is a sequence of format specifiers and literal characters that
indicate how the source material is to be combined into the target.
Examples of format strings for the formatting functions are as follows.
"%s < RANGE %i"
"%s < %s; %i"

The character < is a visual reminder of the direction of the data transformation (that is, from the
sources to the target), and also separates the single target format specifier from the (perhaps
multiple) source format specifiers and literals. The target format specifier can be omitted, in
which case a %s string format is assumed. If the target format specifier is omitted, the
< character can be omitted also, or retained for clarity.
Notice that the target format specifier is located to the left of the < symbol, just as the target
parameter is located to the left of the format string. Likewise, the source format specifiers are
located to the right of the < symbol, just as the source parameters are located to the right of the
format string.

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Format specifiers describe the inputs and outputs of data transformations. Each format specifier
has the following form.
%

[ rep ]

formatcode

[[ modifiers ]]

The character % introduces all format specifiers. rep indicates how many times the format
repeats with respect to the arguments. formatcode is a code character which indicates the
nature of the data items being formatted. modifiers is an optional bracket-enclosed sequence
of codes which further describe the data format.
Examples of format specifiers are as follows.
%s

%100f

%i[b2u]

Note: rep is not allowed when formatcode is s (string).
formatcode is specified with one of the following codes:
s string. As a source or target specifier, this indicates that the corresponding parameter is a
character string. As a target specifier (the default if no target specifier is present), this
can mean that numeric source parameters become converted into an ASCII form for
inclusion in the target string. See the individual numeric formats, such as %i and %f, for
details of these conversions. Arrays of strings are not allowed. For example, %10s is not
a valid format string.
Note: When a target string is filled in, an ASCII NUL is always placed in the string
after the last byte.
i integer. This source or target specifier indicates that the corresponding parameter is an
integer or, if rep is present, an integer array. The function performs conversions to
ASCII digits when converting to or from the string format %s. A modifier is available to
specify the radix to be used in such a conversion (default is decimal).
x integer (hexadecimal). This source or target specifier indicates that the corresponding
parameter is an integer or, if rep is present, an integer array. The function performs
conversions to ASCII hexadecimal digits (0123456789abcdef) when converting to or
from the string format %s.
o integer (octal). This source or target specifier indicates that the corresponding parameter
is an integer or, if rep is present, an integer array. The function performs conversions to
ASCII octal digits (01234567) when converting to or from the string format %s.
d integer (decimal). This format specifier is identical to %i and is included for
compatibility with the C printf family of functions.

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f real number. This source or target specifier indicates that the corresponding parameter is
a real number, or if rep is present, a real array. The function performs conversions to
ASCII when converting to or from the string format %s.
c character. This source or target specifier indicates that the corresponding parameter is an
integer with one significant byte, or, if rep is present, an array of 1-byte integers. The
function does not perform conversion to ASCII when converting to or from the string
format %s. The byte is copied directly to or from the string.
Formatting Modifiers
modifiers are optional codes used to describe the nature of the source or target data. If you
use them, you must enclose the modifiers in square brackets and place them immediately after
the format code they modify. If one format specifier requires more than one modifier, enclose all
modifiers in the same set of brackets.
There is a different set of modifiers for each possible format specifier.
Formatting Integer Modifiers (%i, %d, %x, %o, %c)
bn

Specify Length. The b integer modifier specifies the length of the integer
argument, or the length of an individual integer array element, in bytes. The
default length is 4 B; therefore, simple 4 B integers do not need this modifier.
The modifier b2 represents short integers. The modifier b1 represents single-byte
integers.

in

Specify Array Offset. The i integer modifier specifies an offset within an
integer array argument. It indicates the location within the array where processing
begins. n is the zero-based index of the first element to process. Thus,
%10d[i2] applied to a source integer array reads the 10 integer values from the
third through the twelfth elements of the array. The i modifier is valid only if
rep is present. If you use the i modifier with the z modifier, then n is in terms
of bytes.

z

Treat String as Integer Array. The z integer modifier indicates that the data
type of the corresponding argument is a string. Nevertheless, the data in the string
is treated as an integer array. The z modifier is valid only if rep is present.

rn

Specify Radix. The r integer modifier specifies the radix of the integer
argument, which is important if the integer was to be converted into string format.
Legal radixes are 8 (octal), 10 (decimal, the default), 16 (hexadecimal), and 256 (a
special radix representing single 8-bit ASCII characters).

wn

Specify String Size. The w integer modifier specifies the exact number of bytes
in which to store a string representation of the integer argument, in the event that

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the integer is converted to a string format. You can enter any non-negative value
here. If n is less than the number of digits required to represent the integer, an
asterisk (*) will be inserted into the string to signify an overflow. The default for
n is zero, which indicates that the integer can occupy whatever space is necessary.
pc

Specify Padding. The p integer modifier specifies a padding character c, which
fills the space to the left of an integer in the event it does not require the entire
width specified with the wn modifier. The default padding character is a blank.

s

Specify as Two’s Complement. The s integer modifier indicates that the integer
argument is considered a signed two's complement number. This is the default
interpretation of integers, so the s modifier is never explicitly required.

u

Specify as Unsigned. The u integer modifier indicates that the integer is
considered an unsigned integer.

onnnn

Specify Byte Ordering. The o integer modifier is used to describe the byte
ordering of raw data so that LabWindows/CVI can map it to the byte order
appropriate for the Intel (PC) or Motorola (SPARCstation) architecture. The
number of n's must be equal to the byte size of the integer argument as specified
by the bn modifier, which must precede the o modifier. In the case of a four-byte
integer, o0123 indicates that the bytes are in ascending order of precedence (Intel
style), and o3210 indicates that the bytes are in descending order of precedence
(Motorola style).
In a Fmt function, the buffer containing the raw instrument data should have the
o modifier describing the byte ordering. The buffer without the o modifier is
guaranteed to be in the mode of the host processor. In other words,
LabWindows/CVI will reverse the byte ordering of the buffer without the
o modifier depending on which architecture the program is running on.
For example, if your GPIB instrument sends two-byte binary data in Intel byte
order, your code should appear as follows:
short int instr_buf[100];
short int prog_buf[100];
status = ibrd (ud, instr_buf, 200);
Fmt (prog_buf, "%100d<%100d[b2o01]", instr_buf);

If, instead, your GPIB instrument sends two-byte binary data in Motorola byte
order, the Fmt function should appear as follows:
Fmt (prog_buf, "%100d<%100d[b2o10]", prog_buf);

In either case, the o modifier is used only on the buffer containing the raw data
from the instrument (instr_buf). LabWindows/CVI will ensure that the
program buffer (prog_buf) is in the proper byte order for the host processor.

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Note: When using both the bn and on modifiers on an integer specifier, the bn modifier
must be first.
Formatting Floating-Point Modifiers (%f)
bn

Specify Length. The b floating-point modifier specifies the length of the
floating-point argument, or the length of an individual array element, in bytes. The
default length is 8 bytes; therefore, double-precision values do not need this modifier.
Single-precision floating-point values are indicated by b4. 8 and 4 are the only valid
values for n.

in

Specify Array Offset. You use the i modifier to specify an offset within a
floating-point array argument. It indicates the location within the array where
processing is to begin. n is the zero-based index of the first element to process.
Thus, %10f[i2] applied to a source floating-point array reads the 10 floating-point
values from the third through the twelfth elements of the array. The i modifier is
valid only if rep is present. If the i modifier is used with the z modifier, then n is in
terms of bytes.

z

Treat String as Floating-Point Array. The z floating-point modifier indicates that
the data type of the corresponding argument is a string. Nevertheless, the data in the
string is treated as a floating-point array. The z modifier is valid only if rep is
present.

wn

Specify String Size. The w floating-point modifier specifies the exact number of
bytes in which to store a string representation of the floating-point argument, in the
event that the value is converted to a string format. Any non-negative value can be
entered here. If n is less than the number of digits required to represent the
floating-point number, an asterisk (*) will be inserted into the string to signify an
overflow. The default for n is zero, which indicates that the value can occupy
whatever space is necessary.

pn

Specify Precision. The p floating-point modifier specifies the number of digits to the
right of the decimal point in a string representation of the floating-point number. You
can lose significant digits by attempting to conform to the precision specification. If
the pn modifier is omitted, the default value is p6.

en

Specify as Scientific Notation. The e floating-point modifier specifies that a value
be converted to string format in scientific notation. If omitted, floating-point notation
is used. n is optional and specifies the number of digits in the exponent. For
example, %f[e2] formats 10.0 as 1.0e+01. If n is omitted, a default of three is used.

f

Specify as Floating-Point Notation. The f floating-point modifier specifies the
value to be converted to string format in floating-point notation. This is the default.

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t

Truncate. The t floating-point modifier indicates that in floating-point to integer
transformations, the floating-point value is truncated instead of rounded. This is the
default.

r

Round. The r floating-point modifier indicates that in floating-point to integer
transformations, the floating-point value is rounded instead of truncated. The default
method is truncation.

Note: The value can be represented in scientific notation even when the e modifier is absent.
This occurs when the absolute value of the argument is greater than 1.0e40 or less
than 1.0e-40, or when the absolute value of the argument is greater than 1.0e20 or less
than 1.0e-4 and neither the p modifier nor the w modifier is present.
Formatting String Modifiers (%s)
in

Specify Array Offset. The i string modifier specifies an offset within a string. It
indicates the location within the string where processing is to begin. n is the zerobased index of the first byte to process. Thus, %s[i2] applied to a target string
begins placing data in the third byte of the string.

a

Append. When applied to a target format specifier, the a string modifier specifies
that all formatted data be appended to the target string. The data is appended
beginning at the first occurrence of an ASCII NUL in the target string.

wn

Specify String Size. When modifying a source format specifier, the w string modifier
specifies the maximum number of bytes to be consumed from the string argument.
You can enter any non-negative value here, the default being zero, which indicates
that the entire string should be consumed.
When modifying a target format specifier, the w string modifier specifies the exact
number of bytes to store in the string, excluding the terminating ASCII NUL. If n is
zero or omitted, as many bytes are stored as are called for by the sources. When n is
greater than the number of bytes available from the source, the remaining bytes are
filled with ASCII NULs if the q modifier is used, or blanks if the q modifier is not
present.
When the w string modifier is used in conjunction with the a string modifier, n
indicates the number of bytes to append to the string excluding the terminating ASCII
NUL.
If wn modifies a target string and n is larger than the number of bytes in the target
argument, the target string is overwritten in compiled C.

q

Append NULs. When applied to a target string in conjunction with the w string
modifier, the q string modifier specifies that unfilled bytes at the end of the target
string be set to ASCII NULs instead of blanks.

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tn

Terminate on Character. When applied to a source string, the t string modifier
specifies that the source string is terminated on the first occurrence of the character n,
where n is the ASCII value of the character. Thus, %s[t44] causes reading of the
source string to stop on an ASCII comma. Using %s[t44] and the source string
Hello, World! as an example, Hello is placed into the target. More than one
t modifier can occur in the same specifier, in which case the string terminates when
any of the terminators occur. If no t modifier is present, reading of the source string
stops on an ASCII NUL. This modifier has no effect when applied to the target
specifier.

t-

Terminate when Full. This is similar to tn, except that it specifies that there are no
terminating characters. Reading of the source string terminates when the target is full
or when the number of bytes specified with the w modifier have been read.

t#

Terminate on Number. This is equivalent to repeating the t modifier with the
ASCII values of the characters +, -, and 0 through 9. It specifies that reading of the
source string be terminated upon occurrence of a numeric expression. Using %s[t#]
with the source string ab567, ab is placed in the target.

Fmt, FmtFile, FmtOut—Asterisks (*) Instead of Constants in Format Specifiers
Often, one or more integer values are required in a format specifier. The format specifier for an
integer array, for example, requires the number of elements (rep). You can use constants for
these integer values in format specifiers. Alternatively, you can specify an integer value using an
argument in the argument list. When you use this method, substitute an asterisk (*) for the
constant in the format specifier.
You can use the asterisk in the following format specifier elements:
rep
in
wn
pn
en
rn

For integer or floating-point arrays
For integer or floating-point arrays, or strings
For any format specifier
For floating-point specifiers only
For floating-point specifiers only
For integer specifiers only

When you use one or more asterisks instead of constants in a target specifier, the arguments
corresponding to the asterisks must appear after the format string in the same order as their
corresponding asterisks appear in the format specifier.
When you use one or more asterisks instead of constants in a source specifier, the arguments
corresponding to the asterisks must precede the source argument and must be in the same order
as their corresponding asterisks in the format specifier.

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Fmt, FmtFile, FmtOut—Literals in the Format String
Literal characters appearing in a formatting function format string indicate that the literal
characters are to be combined with the source parameters in the appropriate positions. They do
not correspond to any source parameters, but are copied directly into the target item.
Since the left side of the < symbol must be a single format specifier, literal characters if present
must be on the right side of the symbol. Literals on the left side or more than one format
specifier on the left side result in a -1 error, indicating a faulty format string. You then can use
the function GetFmtErrNdx to determine exactly where the error lies in the format string.
The characters %, [, ], <, and > have special meaning in the format strings. To specify that these
characters be taken literally, they should be preceded by %.

Scanning Functions
The following information is a brief description of the three scanning functions.
•

n = Scan (source, formatstring, targetptr1, ..., targetptrn);

The Scan function inspects the source argument and applies transformations to it
according to descriptions in the formatstring argument. The results of the
transformations are placed into the targetptr1 ... targetptrn arguments.
•

n = ScanFile (handle, formatstring, targetptr1, ..., targetptrn);

The ScanFile function reads data from the file corresponding to the handle argument
and applies transformations to it according to descriptions in the formatstring argument.
The results of the transformations are placed into the targetptr1 ... targetptrn
arguments.
•

n = ScanIn (formatstring, targetptr1, ..., targetptrn);

The ScanIn function reads data from standard input and applies transformations to it
according to descriptions in the formatstring argument. The results of the
transformations are placed into the targetptr1 ... targetptrn arguments.
All of the above functions return the number of target format specifiers satisfied. The
function returns a -1 if there is an error in the format string.
The scanning functions break apart a source item into component parts and store the parts into
parameters passed to the function. The only difference between the three functions is the
location of the source data. For the function Scan, the source item is a data item in memory
which is passed to the function. For ScanFile, the source item is a file, whose handle is
passed as the first argument. The handle is obtained by a call to the LabWindows/CVI function
OpenFile. For the function ScanIn, the source is taken from Standard In (typically the
keyboard), and the source argument present in the other two functions is omitted.
All target parameters must be passed by reference.

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Scanning Functions—Format String
Consider the following scanning function:
n = Scan(source, formatstring, targetptr1, ..., targetptrn);

where formatstring contains the information to transform the source argument to the
targetptr arguments.
Format strings for the scanning functions are of the following form.
"source_spec > target_specs_and_literals"

where source_spec is a format specifier that describes the nature of the source parameter and
target_specs_and_literals is a sequence of format specifiers and literal characters that
indicate how to divide and reformat the source argument into the desired target.
Examples of format strings for the scanning functions are:
"%s > %i"

"%s > %20f[w10x]"

The character > is a visual reminder of the direction of the data transformation, and also
separates the single source format specifier from the (possibly multiple) target format specifiers
and literals. The source format specifier can be omitted, in which case a %s string format is
assumed. If the source format specifier is omitted, the > character can be omitted also, or
retained for clarity.
Notice that the source format specifier is located to the left of the > symbol, just as the source
parameter is located to the left of the format string. Likewise, the target format specifiers are
located to the right of the > symbol, just as the target parameters are located to the right of the
format string.
Format specifiers describe the inputs and outputs of data transformations. Each format specifier
is of the following form.
%

[ rep ]

formatcode

[[ modifiers ]]

The character % introduces all format specifiers. rep indicates how many times the format
repeats with respect to the arguments. formatcode is a code character which indicates the
nature of the data items being formatted. modifiers is an optional bracket enclosed sequence
of codes which further describe the data format.
The following are examples of format specifiers.
%s[t59]

%100i[z]

%f

Note: rep is not allowed when formatcode is s or l (string).

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formatcode is specified with one of the following codes:
s string. As a source or target specifier this indicates that the corresponding parameter is a
character string. As a source specifier the number of bytes of the source parameter that
are consumed depends on the target specifier. If the target specifier is %s, bytes are
consumed until a termination character is encountered (see the t modifier for strings for
more information on termination characters). If the target specifier is one of the numeric
formats, bytes are consumed as long as they correspond to the pattern for the particular
numeric item being converted. Leading spaces and tabs are skipped unless the y modifier
is used.
Note: When a target string is filled in, an ASCII NUL is always placed in the string
after the last byte.
l string. This is allowed only as a source specifier. It is the same as the %s specifier,
except that bytes from the source argument are to be consumed only until a linefeed is
encountered. Also, when modified with c as in %l[c], a comma is used as the target
string terminator in place of white space characters.
i integer. As a source or target specifier this indicates that the corresponding parameter is
an integer or, if rep is present, an integer array. As a source specifier in conversions to
string formats, the integer is converted into digits of the specified radix (default is
decimal). As a target specifier in conversions from string format, bytes of the source
parameter are consumed as long as they match the pattern of integer ASCII numbers in
the appropriate radix, or until the end of the string is encountered. The scanned
characters are converted to integer values and placed into the corresponding target
parameter, which is an integer or integer array passed by reference. If the format is
repeated, the operation is repeated the appropriate number of times with successive
elements of the integer array parameter.
The pattern for integer ASCII numbers depends on the radix of the number, and consists
of an optional sign (+ or -), followed by a series of one or more digits in the appropriate
radix. The decimal digits are 01234 56789. The octal digits are 01234567. The
hexadecimal digits are 0123456789ABCDEFabcdef.
x integer (hexadecimal). This specifier indicates a %i format with hexadecimal radix.
o integer (octal). This specifier indicates a %i format with octal radix.
d integer (decimal). This specifier indicates a %i format with decimal radix. Since
decimal is the default radix for integers, %d is equivalent to %i, and is included for
compatibility with the C scanf family of functions.

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f real number. As a source or target specifier, this indicates that the corresponding
parameter is a real number, or if rep is present, a real array. As a source specifier in
conversions to string formats, the floating-point value is converted into ASCII form. As
a target specifier in conversions from string format, bytes of the source parameter are
consumed as long as they match the pattern of floating-point ASCII numbers, or until the
end of the string is encountered. The scanned characters are converted to a floating-point
value and placed into the corresponding floating-point or floating-point array target
parameter. If the format is repeated, the operation is repeated the appropriate number of
times with successive elements of the array parameter. The pattern for floating-point
ASCII numbers is an optional sign (+ or -), a series of one or more decimal digits
possibly containing a decimal point, and an optional exponent consisting of an E or e
followed by an optionally signed decimal integer value.
c character. As a source specifier, this indicates that the source parameter is an integer with
one significant byte or, if rep is present, an array of 1-byte integers. As a target specifier
this indicates that a byte of the source parameter is to be consumed, and the scanned
character placed directly into the corresponding target parameter, which is an integer
passed by reference. If the format is repeated, this operation is repeated the appropriate
number of times and the results stored into successive elements of the integer array.
Scanning Modifiers
modifiers are optional codes used to describe the nature of the source or target data. If you
use them, you must enclose the modifiers in square brackets and place them immediately after
the format code they modify. If one format specifier requires more than one modifier, enclose all
modifiers in the same set of brackets. There is a different set of modifiers for each possible
format specifier.
Scanning Integer Modifiers (%i, %d, %x, %o, %c)
bn

Specify Length. The b integer modifier specifies the length of the integer argument,
or the length of an individual integer array element, in bytes. The default length is
4 B; therefore, simple 4 B integers do not need this modifier. The modifier b2
represents short integers. The modifier b1 represents single-byte integers.

in

Specify Array Offset. Use the i integer modifier to specify an offset within an
integer array argument. It indicates the location within the array where processing is
to begin. n is the zero-based index of the first element to process. Thus, %10d[i2]
applied to a source integer array reads the 10 integer values from the third through the
twelfth elements of the array. The i modifier is valid only if rep is present. If the
i modifier is used with the z modifier, then n is in terms of bytes.

z

Treat String as Integer Array. The z integer modifier indicates that the data type of
the corresponding argument is a string. Nevertheless, the data in the string is treated
as an integer array. The z modifier is valid only if rep is present.

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rn

Specify Radix. The r integer modifier specifies the radix of the integer argument,
which is important if the integer is converted from a string format. Legal radixes are
8 (octal), 10 (decimal, the default), 16 (hexadecimal), and 256 (a special radix
representing single 8-bit ASCII characters).

wn

Specify String Size. The w integer modifier specifies the exact number of bytes
occupied by a string representation of the integer argument, in the event that the
integer is converted from a string format. You can enter any non-negative value here.
If n is less than the number of digits required to represent the integer, an asterisk (*)
will be inserted into the string to signify an overflow. The default for n is zero, which
indicates that the integer can occupy whatever room is necessary.

s

Specify as Two’s Complement. The s integer modifier indicates that the integer
argument is to be considered a signed two's complement number. This is the default
interpretation of integers, so the s modifier is not required.

u

Specify as Non-negative. The u integer modifier indicates that the integer is to be
considered a non-negative integer.

x

Discard Terminator. The x integer causes the character that terminated the numeric
data to be discarded. In this way, terminator characters can be skipped when reading
lists of numeric input. Thus, %3i[x] reads three integer numbers, disregarding the
terminator character which appears after each one. You can use this specifier to scan
the string 3, 7, -32.

d

Discard Data. When applied to a target specifier, the d integer modifier indicates
that there is no target argument to correspond to the target specifier. The data that
otherwise is placed in the target argument is discarded instead. The count returned by
the Scan/ScanFile/ScanIn functions will include the target specifier even if the
d modifier is used.

onnnn

Specify Byte Ordering. The o integer modifier is used to describe the byte ordering
of raw data so that LabWindows/CVI can map it to the byte order appropriate for the
Intel (PC) or Motorola (SPARCstation) architecture. The number of n's must be
equal to the byte size of the integer argument as specified by the bn modifier, which
must precede the o modifier. In the case of a four-byte integer, o0123 indicates that
the bytes are in ascending order of precedence (Intel style), and o3210 indicates that
the bytes are in descending order of precedence (Motorola style).
In a Scan function, the buffer containing the raw instrument data should have the
o modifier describing the byte ordering. The buffer without the o modifier is
guaranteed to be in the mode of the host processor. LabWindows/CVI will reverse the
byte ordering of the buffer without the o modifier depending on which architecture
the program is running.
For example, if your GPIB instrument sends two-byte binary data in Intel byte order,
your code should appear as follows.

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short int instr_buf[100];
short int prog_buf[100];
status = ibrd (ud, instr_buf, 200);
Scan (instr_buf, "%100d[b2o01]>%100d", prog_buf);

If, instead, your GPIB instrument sends two-byte binary data in Motorola byte order,
the Scan function should appear as follows.
Scan (instr_buf, "%100d[b2o10]>%100d", prog_buf);

In either case, the o modifier is used only on the buffer containing the raw data from
the instrument (instr_buf). LabWindows/CVI will ensure that the program buffer
(prog_buf) is in the proper byte order for the host processor.
Note: When using both the bn and on modifiers on an integer specifier, the bn modifier
must be first.
Scanning Floating-Point Modifiers (%f)
bn

Specify Length. The b floating-point modifier specifies the length of the
floating-point argument, or the length of an individual array element, in bytes. The
default length is 8 B; therefore, double-precision values do not need this modifier.
Single-precision floating-point values are indicated by b4. 8 and 4 are the only valid
values for n.

in

Specify Array Offset. You can use the i floating-point modifier to specify an offset
within a floating-point array argument. It indicates the location within the array
where processing is to begin. n is the zero-based index of the first element to process.
Thus, %10f[i2] applied to a source floating-point array reads the 10 floating-point
values from the third through the twelfth elements of the array. The i modifier is
valid only if rep is present. If you use the i modifier with the z modifier, then n is
in terms of bytes.

z

Treat String as Floating Point. The z floating-point modifier indicates that the data
type of the corresponding argument is a string. Nevertheless, the data in the string is
treated as a floating-point array. The z modifier is valid only if rep is present.

wn

Specify String Size. The w floating-point modifier specifies the exact number of
bytes occupied by a string representation of the floating-point argument, in the event
that the value is converted from a string format. You can enter any non-negative
value here. If n is less than the number of digits required to represent the
floating-point number, an asterisk (*) will be inserted into the string to signify an
overflow. The default for n is zero, which indicates that the value can occupy
whatever space is necessary.

pn

Specify Precision. The p floating-point modifier specifies the number of digits to the
right of the decimal point in a string representation of the floating-point number.
Significant digits may be lost in attempting to conform to the precision specification.

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If the pn modifier is omitted, a default of p6 is used. The p modifier is valid for
sources only.
en

Specify as Scientific Notation. The e floating-point modifier indicates that the
string representation of the floating-point value is in scientific notation. If omitted,
non-scientific notation is used. n is optional and specifies the number of digits to use
in the exponent. For example, %f[e2] causes 10.0 to be formatted as 1.0e+01. If
n is omitted, a default of three is used. The e modifier is valid for sources only.

f

Specify as Floating Point. The f floating-point modifier indicates that the string
representation of the floating-point value is in non-scientific notation. This is the
default even when the f modifier is not present.

x

Discard Terminator. The x floating-point modifier causes the character that
terminated the numeric data to be discarded. In this way, terminator characters can be
skipped when reading lists of numeric input. Thus, %3f[x] reads three floatingpoint numbers, disregarding the terminator character which appears after each one;
this specifier could then be used to scan the string 3.5, 7.6, -32.4.

d

Discard Data. When applied to a target specifier, the d modifier indicates there is no
target argument to correspond to the target specifier. The data that otherwise is
placed in the target argument is discarded instead. The count returned by the
Scan/ScanFile/ScanIn functions will include the target specifier even if the
d modifier is used.

Scanning String Modifiers (%s)
in

Specify Array Offset. The i string modifier specifies an offset within a string. It
indicates the location within the string where processing is to begin. n is the zerobased index of the first byte to process. Thus, %s[i2] applied to a target string
begins placing data in the third byte of the string.

a

Append. When applied to a target format specifier, the a string modifier specifies
that all formatted data be appended to the target string, beginning at the first
occurrence of an ASCII NUL in the target string.

wn

Specify String Size. When modifying a source format specifier, the w string modifier
specifies the maximum number of bytes from the source string to be used for filling
the target arguments. You can enter any non-negative value here, the default being
zero, which indicates that the entire string can be used. (For ScanFile and
ScanIn, the entire source string is consumed even if the w modifier restricts the
number of bytes used to fill in the target arguments.)
When modifying a target format specifier, the w modifier specifies the exact number
of bytes to store in the string, excluding the terminating ASCII NUL. If n is zero or
omitted, as many bytes are stored as are called for by the sources. When n is greater

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than the number of bytes available from the source, the remaining bytes are filled
with ASCII NULs if the q modifier is used or blanks if the q modifier is not present.
When the w modifier is used in conjunction with the a modifier, n indicates the
number of bytes to append to the string excluding the terminating ASCII NUL.
If wn modifies a target string and n is larger than the number of bytes in the target
argument, the target argument is overwritten in compiled C.
q

Append NULs. When applied to a target string in conjunction with the w string
modifier, the q string modifier specifies that unfilled bytes at the end of the target
string be set to ASCII NULs instead of blanks.

y

Append with Spacing. When the source is a string and the y modifier is applied to a
target string format specifier, the target string is filled with bytes from the source
string without skipping leading spaces or tabs.

tn

Terminate on Character. When applied to a source string, the t modifier specifies
that the source string is terminated on the first occurrence of the character n, where n
is the ASCII value of the character. Thus, %s[t44] causes reading of the source
string to stop on an ASCII comma. More than one t modifier can occur in the same
specifier, in which case the string terminates when any of the terminators occur. If no
t modifier is present, reading of the source string stops on an ASCII NUL.
When applied to a target string that is being filled from a source string, the t modifier
specifies that filling of the target is terminated on the first occurrence of the character
n, where n is the ASCII value of the character. Thus, %s[t59] causes reading of
the source string to stop on an ASCII semicolon. More than one t modifier can occur
in the same specifier, in which case filling of the target terminates when any of the
terminators occur. If no t modifier is present, filling of the target stops on any
whitespace character.

t-

Terminate when Full. This is similar to tn, except that it specifies that there are no
terminating characters. When applied to a source string, t- specifies that reading of
the source string terminates when all of the targets are full or when the number of
bytes specified with the w modifier have been read. When applied to a target string,
t- specifies that filling of the target string terminates when the source is exhausted or
when the number of bytes specified with the w modifier have been placed into the
target.

t#

Terminate on Number. This is equivalent to repeating the t modifier with the
ASCII values of the characters +, -, and 0 through 9. When applied to a source
(target), it specifies that reading of the source string (filling of the target string) be
terminated upon occurrence of a numeric expression. Using %s>%s[t#]%d with the
source string ab567, ab is placed in the first target and the integer 567 is placed in
the second target.

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x

Discard Terminator. When applied to a target string, the x modifier specifies that
the terminating character be discarded before the next target is filled in. Using
%s>%s[xt59]%s[xt59] with the source string "abc;XYZ;", "abc" is placed
in the first target and "XYZ" is placed in the second target.

d

Discard Data. When applied to a target specifier, the d modifier indicates that there
is no target argument to correspond to the target specifier. The data that otherwise is
placed in the target argument is discarded instead. The count returned by the
Scan/ScanFile/ScanIn functions will include the target specifier even if the
d modifier is used.

Scan, ScanFile, ScanIn—Asterisks (*) Instead of Constants in Format Specifiers
Often, a format specifier requires one or more integer values. The format specifier for an integer
array, for example, requires the number of elements (rep). You can use constants for these
integer values in format specifiers. Alternatively, you can specify an integer value using an
argument in the argument list. When you use this method, substitute an asterisk (*) for the
constant in the format specifier. Use the asterisk in the following format specifier elements.
rep
in
wn
pn
en
rn

For integer or floating-point arrays.
For integer or floating-point arrays, or strings.
For any format specifier.
For floating-point specifiers only.
For floating-point specifiers only.
For integer specifiers only.

When you use one or more asterisks instead of constants in a source specifier, the arguments
corresponding to the asterisks must appear after the format string in the same order as their
corresponding asterisks appear in the format specifier.
When you use one or more asterisks instead of constants in a target specifier, the arguments
corresponding to the asterisks must precede the target argument and must be in the same order as
their corresponding asterisks in the format specifier.
Scan, ScanFile, ScanIn—Literals in the Format String
Literal characters appearing in a scanning function format string indicate that the literal
characters are expected in the source parameter. They are not stored into any target parameter,
but are skipped over when encountered. If a literal character specified in the format string fails
to appear in the source in the expected position, the scanning function immediately returns.

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Some formats may have been correctly detected in the input, and the corresponding target
parameters will have been filled in. Formats situated after the literal which did not appear,
however, will not have been executed.
The function return value can be used to determine exactly how many target parameters were
actually fulfilled by the input. You can use the function NumFmtdBytes to determine the
number of bytes consumed from the source parameter.
Because the left side of the > symbol must be a single format specifier, literal characters, if
present, must be on the right side of the symbol. Literals on the left side, or more than one
format specifier on the left side, result in a -1 error, indicating a faulty format string. The
function GetFmtErrNdx can then be used to determine exactly where in the format string the
error lies.
The characters %, [, ], <, and > have special meaning in the format strings. To specify that these
characters be taken literally, they should be preceded by %.

Formatting and I/O Library Programming Examples
This section contains examples of program code that use the Formatting and I/O Library
functions. The formatting and scanning functions are the basis of most of the examples.
The Fmt/FmtFile/FmtOut examples are logically organized as shown:
Integer to String
Long Integer to String
Real to String in Floating-Point Notation
Real to String in Scientific Notation
Integer and Real to String with Literals
Two Integers to ASCII File with Error Checking
Real Array to ASCII File in Columns and with Comma Separators
Integer Array to Binary File, Assuming a Fixed Number of Elements
Real Array to Binary File, Assuming a Fixed Number of Elements
Real Array to Binary File, Assuming a Variable Number of Elements
A Variable Portion of a Real Array to a Binary File
Concatenating Two Strings
Appending to a String
Creating an Array of File Names
Writing a Line Containing an Integer with Literals to the Standard Output
Writing to the Standard Output without a Linefeed/Carriage Return
The Scan/ScanFile/ScanIn examples are logically organized as shown:
String to Integer
String to Long Integer
String to Real
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String to Integer and Real
String to String
String to Integer and String
String to Real, Skipping over Non-Numeric Characters in the String
String to Real, after Finding a Semicolon in the String
String to Real, after Finding a Substring in the String
String with Comma-Separated ASCII Numbers to Real Array
Scanning Strings That Are Not NUL-Terminated
Integer Array to Real Array
Integer Array to Real Array with Byte Swapping
Integer Array Containing 1-Byte Integers to Real Array
String Containing Binary Integers to Integer Array
String Containing an IEEE-Format Real Number to a Real Variable
ASCII File to Two Integers with Error Checking
ASCII File with Comma-Separated Numbers to Real Array, with Number of Elements
at Beginning of File
Binary File to Integer Array, Assuming a Fixed Number of Elements
Binary File to Real Array, Assuming a Fixed Number of Elements
Binary File to Real Array, with Number of Elements at Beginning of File
Reading an Integer from the Standard Input
Reading a String from the Standard Input
Reading a Line from the Standard Input

Fmt/FmtFile/FmtOut Examples in C
This section contains examples of program code that use the Fmt, FmtFile, and FmtOut
functions from the Formatting and I/O Library. To eliminate redundancy, error checking on I/O
operations has been omitted from all of the examples in this section except the Two Integers to
ASCII File with Error Checking example.
Integer to String
char buf[10];
int a;
a = 16;
Fmt (buf, "%s<%i", a);
a = 16;
Fmt (buf, "%s<%x", a);
a = 16;
Fmt (buf, "%s<%o", a);
a = -1;
Fmt (buf, "%s<%i", a);
a = -1;
Fmt (buf, "%s<%i[u]", a);
a = 1234;
Fmt (buf, "%s<%i[w6]", a);
a = 1234;

LabWindows/CVI Standard Libraries

/* result: "16" */
/* result: "10" */
/* result: "20" */
/* result: "-1" */
/* result: "4294967295" */
/* result: "

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Fmt (buf, "%s<%i[w6p0]", a);
a = 1234;
Fmt (buf, "%s<%i[w2]", a);

/* result: "001234" */
/* result: "*4" */

Remarks
The results shown are the contents of buf after each call to Fmt. The last call demonstrates
what occurs when the width specified by the w modifier is too small.

Long Integer to String
char buf[20];
long a;
a = 123456;
Fmt (buf, "%s<%i[b4]", a);
a = 123456;
Fmt (buf, "%s<%x[b4]", a);
a = 123456;
Fmt (buf, "%s<%o[b4]", a);
a = -1;
Fmt (buf, "%s<%i[b4]", a);
a = -1;
Fmt (buf, "%s<%i[b4u]", a);
a = 123456;
Fmt (buf, "%s<%i[b4w8]", a);
a = 123456;
Fmt (buf, "%s<%i[b4w8p0]", a);
a = 123456;
Fmt (buf, "%s<%i[b4w4]", a);

/* result: "123456" */
/* result: "1e240" */
/* result: "361100" */
/* result: "-1" */
/* result: "4294967295" */
/* result: "

123456" */

/* result: "00123456" */
/* result: "*456" */

Remarks
The results shown are the contents of buf after each call to Fmt. The last call demonstrates
what occurs when the width specified by the w modifier is too small.

Real to String in Floating-Point Notation
char buf[30]
double x;
x = 12.3456789;
Fmt (buf, "%s<%f", x);
x = 12.3456789;
Fmt (buf, "%s<%f[p2]", x);
x = 12.3456789;
Fmt (buf, "%s<%f[p10]", x);
x = 12.345;
Fmt (buf, "%s<%f", x);
x = 12.345;

© National Instruments Corporation

/* result: "12.345679" */
/* result: "12.35" */
/* result: "12.3456789000" */
/* result: "12.345" */

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Fmt
x =
Fmt
x =
Fmt
x =
Fmt
x =
Fmt
x =
Fmt
x =
Fmt

(buf, "%s<%f[p0]", x);
12.345;
(buf, "%s<%f[p6]", x);
-12.345;
(buf, "%s<%f[w12]", x);
-12.3456789;
(buf, "%s<%f[w6]", x);
0.00000012;
(buf, "%s<%f[p8]", x);
0.00000012;
(buf, "%s<%f", x);
4.5e050;
(buf, "%s<%f", x);

Chapter 2

/* result: "12." */
/* result: "12.345000" */
/* result: "-12.345" */
/* result: "-12.3*" */
/* result: "0.00000012" */
/* result: "1.2e-007" */
/* result: "4.5e050" */

Remarks
The results shown are the contents of buf after each call to Fmt. The last two calls demonstrate
that very large and very small values are sometimes forced into scientific notation even when the
e modifier is absent.

Real to String in Scientific Notation
char buf[20];
double x;
x = 12.3456789;
Fmt (buf, "%s<%f[e]", x);
x = 12.3456789;
Fmt (buf, "%s<%f[ep2]", x);
x = 12.3456789;
Fmt (buf, "%s<%f[e2p2]", x);
x = 12.345;
Fmt (buf, "%s<%f[e]", x);
x = 12.345;
Fmt (buf, "%s<%f[ep2w12]", x);
x = 12.345;
Fmt (buf, "%s<%f[ep2w6]", x);

/* result: "1.234568e+001" */
/* result: "1.23e+001" */
/* result: "1.23e+01" */
/* result: "1.234500e+001" */
/* result: "

1.23e+001" */

/* result: "1.23e*" */

Remarks
The results shown are the contents of buf after each call to Fmt. The last call demonstrates
what occurs when the width specified by the w modifier is too small.

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Integer and Real to String with Literals
char buf[20];
int f, r;
double v;
f = 4;
r = 3;
v = 1.2;
Fmt (buf, "%s%i",
s = "-32";
n = Scan (s, "%s>%i",
s = "
+32";
n = Scan (s, "%s>%i",
s = "x32";
n = Scan (s, "%s>%i",

&a);

/* result: a = 32, n = 1 */

&a);

/* result: a = -32, n = 1 */

&a);

/* result: a = 32, n = 1 */

&a);

/* result: a = ??, n = 0 */

Remarks
When locating an integer in a string, Scan skips over white space characters such as spaces,
tabs, linefeeds, and carriage returns. If a non-numeric character other than a white space
character, +, or - is found before the first numeric character, the Scan call fails. Thus, Scan
fails on the x in x32; it leaves the value in a unmodified and returns zero, indicating that no
target specifiers were satisfied.
s
n
s
n
s
n
s
n

=
=
=
=
=
=
=
=

"032";
Scan (s,
"32a";
Scan (s,
"32";
Scan (s,
"32";
Scan (s,

"%s>%i", &a);

/* result: a = 32, n = 1 */

"%s>%i", &a);

/* result: a = 32, n = 1 */

"%s>%o", &a);

/* result: a = 26, n = 1 */

"%s>%x", &a);

/* result: a = 50, n = 1 */

Remarks
When the %i specifier is used, numeric characters are interpreted as decimal, even when they
might appear to be octal (as in 032) or hexadecimal (as in 32a). When the %o specifier is
used, the numeric characters (01234567) are always interpreted as octal. When the %x
specifier is used, the numeric characters (0123456789abcdef) are always interpreted as
hexadecimal.
s = "32x1";
n = Scan (s, "%s>%i", &a);

© National Instruments Corporation

/* result: a = 32, n = 1 */

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Scan considers the occurrence of a non-numeric character (such as the x in 32x1) to mark the
end of the integer.
s = "32567";
n = Scan (s, "%s>%i[w3]", &a);

/* result: a = 325, n = 1 */

The w3 modifier specifies that only the first 3 bytes of the string are scanned.

String to Long Integer
char *s;
long a;
int n;
s = "99999";
n = Scan (s, "%s>%i[b4]", &a);
s = "303237";
n = Scan (s, "%s>%o[b4]", &a);
s = "ffff";
n = Scan (s, "%s>%x[b4]", &a);

/* result: a = 99999, n = 1 */
/* result: a = 99999, n = 1 */
/* result: a = 65535, n = 1 */

Remarks
Scan extracts long integers from strings in the same way it extracts integers. The only
differences are that the b4 modifier must be used and the target argument must be a long integer.
See the String to Integer example earlier in this section for more details on using Scan to extract
integers and long integers from strings.

String to Real
char *s;
double x;
int n;
s = "12.3";
n = Scan (s, "%s>%f", &x); /* result: x = 12.3, n = 1 */
s = "-1.23e+1";
n = Scan (s, "%s>%f", &x); /* result: x = -1.23, n = 1 */
s = "1.23e-1";
n = Scan (s, "%s>%f", &x); /* result: x = 0.123, n = 1 */

Remarks
When locating a real number in a string, Scan accepts either floating-point notation or scientific
notation.
s
n
s
n

=
=
=
=

"
12.3";
Scan (s, "%s>%f", &x); /* result: x = 12.3, n = 1 */
"p12.3";
Scan (s, "%s>%f", &x); /* result: x = ????, n = 0 */

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When locating a real number in a string, Scan skips over white space characters. If a nonnumeric character other than a white space character, +, or - is found before the first numeric
character, the Scan call fails. Thus, Scan fails on the p in p12.3; it leaves the value in x
unmodified and returns zero, indicating that no target specifiers were satisfied.
s
n
s
n
s
n

=
=
=
=
=
=

"12.3m";
Scan (s, "%s>%f", &x); /* result: x = 12.3, n = 1 */
"12.3.4";
Scan (s, "%s>%f", &x); /* result: x = 12.3, n = 1 */
"1.23e";
Scan (s, "%s>%f", &x); /* result: x = ????, n = 0 */

Scan considers the occurrence of a non-numeric character (such as the m in 12.3m) to mark the
end of the real number. A second decimal point also marks the end of the number. However,
Scan fails on "1.23e" because the value of the exponent is missing.
s = "1.2345";
n = Scan (s, "%s>%f[w4]", &x);/* result: x = 1.23, n = 1 */

The w4 modifier specifies that only the first 4 bytes of the string are scanned.

String to Integer and Real
char *s;
int a, n;
double x;
s = "32
1.23";
n = Scan (s, "%s>%i%f", &a, &x);
/* result: a = 32, x = 1.23, n = 2 */
s = "32, 1.23";
n = Scan (s, "%s>%i[x]%f", &a, &x);
/* result: a = 32, x = 1.23, n = 2 */
s = "32, 1.23";
n = Scan (s, "%s>%i%f", &a, &x);
/* result: a = 32, x = ????, n = 1 */

Remarks
After each of the first two calls to Scan, a = 32, x = 1.23, and n = 2 (indicating that two target
specifiers were satisfied). In the second call, the x modifier is used to discard the separating
comma.
In the third call, there is a comma separator after the integer, but the x modifier is absent.
Consequently, Scan fails when attempting to find the real number. x remains unmodified, and
n = 1 (indicating that only one target specifier was satisfied).

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String to String
char *s;
char buf[10];
int n;
s = " abc ";
n = Scan (s, "%s>%s", buf);
s = " abc ";
n = Scan (s, "%s>%s[y]", buf);

/* result: buf = "abc" */
/* result: buf = "

abc" */

Remarks
When extracting a substring from a string, Scan skips leading spaces and tabs unless the y
modifier is present.
s
n
s
n

=
=
=
=

"a b c; d";
Scan (s, "%s>%s", buf);
/* result: buf = "a" */
"a b c; d";
Scan (s, "%s>%s[t59]", buf); /* result: buf = "a b c" */

When Scan extracts a substring from a string and the t modifier is not present, the substring is
considered to be terminated by a white space character. To include embedded white space in the
target string, use the t modifier to change the target string termination character. In the second
call to Scan, [t59] changes the termination character to a semicolon (ASCII 59).
s = " abcdefghijklmnop";
n = Scan (s, "%s>%s[w9]", buf);
s
n
s
n

=
=
=
=

/* result: buf = "abcdefghi" */
" abc";
Scan (s, "%s>%s[w9]", buf); /* result: buf = "abc "*/
" abc"
Scan (s, "%s>%s[w9q]", buf); /* result: buf = "abc" */

Remarks
The w modifier can be used to prevent Scan from writing beyond the end of a target string. The
width specified does not include the ASCII NUL that Scan places at the end of the target string.
Therefore, the width specified should be at least one less than the width of the target character
buffer.
When the w modifier is used and the string extracted is smaller than the width specified, the
remaining bytes in the target string are blank-filled. However, if the q modifier is also used,
ASCII NULs fill the remaining bytes.

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String to Integer and String
char *s;
char buf[10];
int a, n;
s = "32abc";
n = Scan (s, "%s>%i%s", &a, buf);
/* result: a = 32, buf = "abc", n = 2 */
s = "32abc";
n = Scan (s, "%s>%i %s", &a, buf);
/* result: a = 32, buf = ?????, n = 1 */

Remarks
After the first call to Scan, a = 32, buf = "abc", and n = 2. Notice there are no spaces in the
format string between the two target specifiers. In the second call, there is a space between %i
and %s. Consequently, Scan expects a space to occur in s immediately after the integer.
Because there is no space in s, Scan fails at that point. It leaves buf unmodified and returns 1
(indicating that only one target specifier is satisfied).
Note: Do not put spaces between specifiers in Scan, ScanFile, or ScanIn format strings.

String to Real, Skipping over Non-Numeric Characters in the String
char *s;
double x;
int n;
s = "VOLTS =
n = Scan (s,
s = "VOLTS =
n = Scan (s,
s = "VOLTS =
n = Scan (s,

1.2";
"%s>%s[dt#]%f", &x);
1.2";
"%s[i8]>%f", &x);
1.2";
"%s>VOLTS = %f", &x);

/* result: x = 1.2, n = 2 */
/* result: x = 1.2, n = 1 */
/* result: x = 1.2, n = 1 */

Remarks
The three different format strings represent different methods for skipping over non-numeric
characters. In the first call, the format string contains two target specifiers. In the first specifier
(%s[dt#]), the t# modifier instructs Scan to read bytes from s until a number is
encountered. The d modifier indicates that the bytes must be discarded because there is no
argument corresponding to the specifier. When the Scan call succeeds, it returns 2, indicating
that two target specifiers were satisfied, even though there is only one target argument.
In the second call, the source specifier %s[i8] instructs Scan to ignore the first 8 bytes of s.
This method works only if the location of the number within s is always the same.
In the third call, the format string contains the non-numeric characters literally. This method
works only if the non-numeric characters in s are always the same.

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String to Real, After Finding a Semicolon in the String
char *s;
double x;
int n;
s = "TIME 12:45:00; 7.34";
n = Scan (s, "%s>%s[xdt59]%f", &x);
/* result: x = 7.34, n = 2 */

Remarks
Some strings returned by programmable instruments contain headers that consist of numeric as
well as non-numeric data and are terminated by a particular character, such as a semicolon. This
example shows how such a header can be skipped.
The format string contains two target specifiers. In the first specifier (%s[xdt#]), the t#
modifier instructs Scan to read bytes from s until a number is encountered. The d modifier
indicates that the bytes must be discarded because there is no argument corresponding to the
specifier. The x modifier indicates that the semicolon should also be discarded.
When the Scan call succeeds, it returns 2, indicating that two target specifiers were satisfied,
even though there is only one target argument.

String to Real, After Finding a Substring in the String
char *s;
double x;
int index, n;
s = "HEADER: R5 D6; DATA 3.71E+2";
index = FindPattern (s, 0, -1, "DATA", 0, 0) + 4;
n = Scan (s, "%s[i*]>%f", index, &x);
/* result: x = 371.0, n = 1 */

Remarks
This example is similar to the previous one, except that portion of the string to be skipped is
terminated by a substring (DATA) rather than by a single character. The Formatting and I/O
Library function FindPattern is used to find the index where DATA begins in s. Four is
added to the index so that it points to the first byte after DATA. The index is then passed to
Scan and matched with the asterisk (*) in the format string.
In this example, FindPattern returns 15, and index is 19. When index is matched to the
asterisk in the format string in the Scan call, the format string is interpreted as %s[i19]>%f.
The i19 indicates that the first 19 bytes of s should be ignored. Scan then extracts the real
number from the remaining string, 3.71E+2, and assigns it to x. Scan returns 1, indicating
that one target specifier is satisfied.

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String with Comma-Separated ASCII Numbers to Real Array
char *s;
int n;
double a[5];
/* 5 8-byte real numbers */
s = "12.3, 45, 6.5, -1.3E-2, 4";
n = Scan (s, "%s>%5f[x]", a);
/* result: a[0] = 12.3,
a[1] = 45.0, a[2] = 6.5, */
/*
a[3] = -0.013, a[4] = 4.0, n = 1 */

Remarks
The x modifier causes the comma separators to be discarded.
Scan considers an array target to be satisfied when at least one element of the array is filled in.
If the source string in this example were 12.3, only the first element of a would be filled in, the
other elements would remain unmodified, and Scan would return 1.

Scanning Strings That Are Not NUL-Terminated
int bd;
double x;
char s[20];
ibrd (bd, s, 15);
Scan (s, "%s[w*]>%f", ibcnt, &x);

Remarks
All of the previous examples assume that s is a NUL-terminated string. However, when reading
data from programmable instruments using the GPIB and RS-232 Library functions, the data
transferred is not NUL-terminated. This example uses ibrd to read up to 15 B from a GPIB
instrument. The global variable ibcnt contains the actual number of bytes transferred. Scan
uses the value in ibcnt in conjunction with the w modifier to specify the width of the source
string.
For example, if ibcnt is 12, the format string is interpreted as %s[w12]>%f, causing Scan to
use only the first 12 bytes of s.
The following example is an alternative method for handling strings that are not
NUL-terminated:
int bd;
double x;
char s[20];
ibrd (bd, s, 15);
s[15] = 0; /* ASCII NUL is 0 */
Scan (s, "%s>%f", &x);

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This code shows how to insert an ASCII NUL at the end of the transferred bytes. After the
assignment, s is NUL-terminated.

Integer Array to Real Array
int ivals[100];
double dvals[100];
Scan (ivals, "%100i>%100f", dvals);

Remarks
Each integer in ivals is converted to real number and then written into dvals.

Integer Array to Real Array with Byte Swapping
int ivals[100];
double dvals[100];
Scan (ivals, "%100i[o10]>%100f", dvals);

Remarks
Each integer in ivals is byte-swapped, converted to a real number, and written into dvals.
Byte swapping is useful when a programmable instrument sends back 2-byte integers with the
high byte first, followed by the low byte. When this data is read into an integer array, the
placement of the bytes is such that the high byte is interpreted as the low byte. The
o10 modifier specifies that the bytes be interpreted in the opposite order.

Integer Array Containing 1-Byte Integers to Real Array
int ivals[50];
/* 100 1-byte integers */
double dvals[100];
/* 100 8-byte real numbers */
Scan (ivals, "%100i[b1]>%100f", dvals);
Scan (ivals, "%100i[b1u]>%100f", dvals);

Remarks
Sometimes, each element in an integer array is used to store two 1-byte integers. This example
shows how to unpack the 1-byte integers and store them in a real array. The b1 indicates that
each binary integer is only one byte long.

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The first call to Scan treats the 1-byte integers as signed values (from -128 to +127). The
second call includes a u in the format string. This causes Scan to treat the 1-byte integers as
unsigned values (from 0 to 255).

String Containing Binary Integers to Integer Array
char s[200];
/* string containing 100 2-byte integers */
int ivals[100];/* 100 2-byte integers */
Scan (s, "%100i[z]>%100i", ivals);
Scan (s, "%97i[zi6]>%97i", ivals);

Remarks
Sometimes data from a programmable instrument is read into a character buffer even though it
contains binary data. This example shows how to treat a character buffer as an integer array.
The format string in each Scan call specifies that the source (s) contains an array of 100
integers. The z modifier is used to indicate that the source is actually a character buffer.
In some cases, the integer data may not start at the beginning of the character buffer. For
instance, the data in the buffer can begin with an ASCII header. In the second call to Scan, the
i6 modifier is used to indicate that the first 6 bytes of s are to be ignored.
Note: When the i modifier is used in conjunction with a character buffer, the number
following the i specifies the number of bytes within the buffer to ignore. This is true
even when the z modifier is also present. On the other hand, when the i modifier is
used in conjunction with an array variable, the number following the i indicates the
number of array elements to ignore.

String Containing an IEEE-Format Real Number to a Real Variable
char s[100];
double x;
Scan (s, "%1f[z]>%f", &x);
Scan (s, "%1f[zi5]>%f", &x);

Remarks
This example is similar to the previous example, except that s contains a single binary real
number (in IEEE format), rather an array of binary integers. The format string in each Scan call
indicates that the source (s) is to be treated as a 1-element array of real numbers. The z modifier
indicates that the source is actually a character buffer. The repetition count of 1 in the format
string is required; otherwise, the z modifier is not accepted.

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The first call to Scan assumes that the real number is at the beginning of s. The second call
assumes that the real number starts at the sixth byte of s. The i5 modifier causes the first
5 bytes of s to be ignored.

ASCII File to Two Integers with Error Checking
int file_handle, n, a, b;
file_handle = OpenFile ("FILE.DAT", 1, 2, 1);
if (file_handle < 0) {
FmtOut ("Error opening file\n");
exit (1);
}
n = ScanFile (file_handle, "%s>%i%i", &a, &b);
if (n != 2) {
FmtOut ("Error reading file\n");
exit (1);
}
CloseFile (file_handle);

Remarks
OpenFile opens the file FILE.DAT as an ASCII file for reading only. If OpenFile
succeeds in opening the file, it returns a file handle with a positive integer value. ScanFile
reads the ASCII representation of two integer values from the file. If ScanFile succeeds, it
returns 2 (indicating that two target specifiers were satisfied).

ASCII File with Comma Separated Numbers to Real Array, with Number of Elements at
Beginning of File
double values[1000];
int file_handle, count;
file_handle = OpenFile ("FILE.DAT", 1, 2, 1);
ScanFile (file_handle, "%s>%i", &count);
if (count > 1000) {
FmtOut ("Count too large\n");
exit(1);
}
ScanFile (file_handle, "%s>%*f[x]", count, values);
CloseFile (file_handle);

Remarks
The first ScanFile call reads the number of elements into the integer variable count. If the
value in count exceeds the number of elements in the real array values, an error is reported.
Otherwise, the second ScanFile call matches count to the asterisk (*) in the format string. It

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then reads the correct number of elements into values. The x modifier causes the comma
separators to be discarded.

Binary File to Integer Array, Assuming a Fixed Number of Elements
int readings[100];
int file_handle, nbytes;
file_handle = OpenFile ("FILE.DAT", 1, 2, 0);
ScanFile (file_handle, "%100i>%100i", readings);
nbytes = NumFmtdBytes ();
CloseFile (file_handle);

Remarks
The ScanFile call reads 100 integers from a binary file and stores them in the integer array
readings. If the ScanFile call is successful, nbytes = 200 (100 integers, 2 bytes per
integer).

Binary File to Real Array, Assuming a Fixed Number of Elements
double waveform[100];
int file_handle, nbytes;
file_handle = OpenFile ("FILE.DAT", 1, 2, 0);
ScanFile (file_handle, "%100f>%100f", waveform);
nbytes = NumFmtdBytes ();
CloseFile (file_handle);

Remarks
The ScanFile call reads 100 real numbers from a binary file and stores them in the real array
waveform. If the ScanFile call is successful, nbytes = 800 (100 integers, 8 bytes per real
number).

Binary File to Real Array, Assuming a Variable Number of Elements
void StoreArray (double x[], int count, char filename[])
{
int file_handle;
file_handle = OpenFile (filename, 1, 2, 0);
ScanFile (file_handle, "%*f>%*f", count, count, x);
CloseFile (file_handle);

}

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Remarks
This example shows how a subroutine can be used to read an array of real numbers from a binary
file. The subroutine takes as parameters a real array, the number of elements to be read, and the
filename.
The ScanFile call reads the first count elements of x from a binary file. The two asterisks
(*) in the format string are matched to count. For instance, if count is 100, then the format
string is equivalent to %100f>100f.

Reading an Integer from the Standard Input
int n, num_readings;
n = 0;
while (n != 1) {
FmtOut ("Enter number of readings: ");
n = ScanIn ("%l>%i", &num_readings);
}

Remarks
This example shows how to get user input from the keyboard. The FmtOut call writes the
prompt string to the screen without a linefeed or carriage return. The ScanIn call attempts to
read an integer value from the keyboard and place it in num_readings. If ScanIn succeeds,
it returns 1, and the loop is exited. Otherwise, the prompt string is repeated.
The format string in the ScanIn call contains a source specifier of %l. This has two
consequences. First, ScanIn returns whenever the user presses ENTER, even if the input line is
empty. This allows the prompt string to be repeated at the beginning of each line until the user
enters an integer value. Second, any characters entered after the integer value are discarded.

Reading a String from the Standard Input
char filename[41];
int n;
n = 0;
while (n != 1) {
FmtOut ("Enter file name: ");
n = ScanIn ("%l>%s[w40q]", filename);
}

Remarks
This example is similar to the previous example, except that the item being read from the
keyboard is a string instead of an integer. The w modifier is used to prevent ScanIn from

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Chapter 2

Formatting and I/O Library

writing beyond the end of filename. Notice that the width specified is one less than the size
of filename. This allows room for the ASCII NUL that ScanIn appends at the end of
filename. The q modifier causes ScanIn to fill any unused bytes at the end of filename
with ASCII NULs. Without the q modifier, all unused bytes are filled with spaces, except for the
ASCII NUL at the end.
The call to ScanIn in this example skips over leading spaces and tabs and terminates the string
on an embedded space. For other options, see the String to String example earlier in this section.

Reading a Line from the Standard Input
char buf[81];
nbytes = ReadLine (0, buf, 80);

Remarks
The previous two examples show how to read single items from the keyboard. When you are
prompted to enter several items on one line, it is often easier to read the entire line into a buffer
before parsing it. This can be done via the Formatting and I/O Library function ReadLine.
The first parameter to ReadLine is a file handle. In this case, the file handle is zero, which is
the handle reserved for the Standard Input. The other two parameters are a buffer and the
maximum number of bytes to place in the buffer. ReadLine always appends an ASCII NUL at
the end of the bytes read. Thus, the maximum number of bytes passed to ReadLine must be at
least one less than the size of the buffer.
ReadLine transfers every character from the input line to the buffer, including leading,
embedded, and trailing spaces, until the maximum number of bytes (for example, 80) have been
transferred. Any remaining characters at the end of the line are discarded. The linefeed is never
transferred to the buffer.
ReadLine returns the number of bytes read, including the number discarded, but excluding the
linefeed.

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Analysis Library
This chapter describes the functions in the LabWindows/CVI Analysis Library. The Analysis
Library Function Overview section contains general information about the Analysis Library
functions and panels. The Analysis Library Function Reference section contains an alphabetical
list of the function descriptions.

Analysis Library Function Overview
The Analysis Library includes functions for one-dimensional (1D) and two-dimensional (2D)
array manipulation, complex operations, matrix operations, and statistics. This section contains
general information about the Analysis Library functions and panels.

The Analysis Library Function Panels
The Analysis Library function panels are grouped in a tree structure according to the types of
operations performed. The Analysis Library function tree is shown in Table 3-1.
The first- and second-level bold headings in the tree are the names of function classes and
subclasses. Function classes and subclasses are groups of related function panels. The thirdlevel headings in plain text are the names of individual function panels. Each analysis function
panel generates one analysis function call. The names of the corresponding analysis function
calls appear in bold italics to the right of the function panel names.
Table 3-1. The Analysis Library Function Tree
Analysis
Array Operations
1D Operations
Clear Array
Set Array
Copy Array
1D Array Addition
1D Array Subtraction
1D Array Multiplication
1D Array Division
1D Absolute Value
1D Negative Value

Clear1D
Set1D
Copy1D
Add1D
Sub1D
Mul1D
Div1D
Abs1D
Neg1D
(continues)

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Chapter 3

Table 3-1. The Analysis Library Function Tree (Continued)
1D Linear Evaluation
1D Maximum & Minimum
1D Array Subset
1D Sort Array
2D Operations
2D Array Addition
2D Array Subtraction
2D Array Multiplication
2D Array Division
2D Linear Evaluation
2D Maximum & Minimum
Complex Operations
Complex Numbers
Complex Addition
Complex Subtraction
Complex Multiplication
Complex Division
Complex Reciprocal
Rectangular to Polar
Polar to Rectangular
1D Complex Operations
1D Complex Addition
1D Complex Subtraction
1D Complex Multiplication
1D Complex Division
1D Complex Linear Evaluation
1D Rectangular to Polar
1D Polar to Rectangular
Statistics
Mean
Standard Deviation
Histogram
Vector & Matrix Algebra
Dot Product
Matrix Multiplication
Matrix Inversion
Transpose
Determinant
Array Utilities
Clear Array
Set Array
Copy Array
Get Error String

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LinEv1D
MaxMin1D
Subset1D
Sort
Add2D
Sub2D
Mul2D
Div2D
LinEv2D
MaxMin2D

CxAdd
CxSub
CxMul
CxDiv
CxRecip
ToPolar
ToRect
CxAdd1D
CxSub1D
CxMul1D
CxDiv1D
CxLinEv1D
ToPolar1D
ToRect1D
Mean
StdDev
Histogram
DotProduct
MatrixMul
InvMatrix
Transpose
Determinant
Clear1D
Set1D
Copy1D
GetAnalysisErrorString

© National Instruments Corporation

Chapter 3

Analysis Library

The classes and subclasses in the function tree are described here.
•

•

The Array Operations function panels perform arithmetic operations on 1D and 2D arrays.
–

1D Operations, a subclass of Array Operations, contains function panels that perform 1D
array arithmetic.

–

2D Operations, a subclass of Array Operations, contains function panels that perform 2D
array arithmetic.

The Complex Operations function panels perform complex arithmetic operations. The
Complex Operations function panels can operate on complex scalars or 1D arrays. The real
and imaginary parts of complex numbers are processed separately.
–

Complex Numbers, a subclass of Complex Operations, contains function panels that
perform scalar complex arithmetic.

–

1D Complex Operations, a subclass of Complex Operations, contains function panels
that perform complex arithmetic on 1D complex arrays.

•

The Statistics function panels perform basic statistics functions.

•

The Vector & Matrix Algebra function panels perform vector and matrix operations.
Vectors and matrices are represented by 1D and 2D arrays, respectively.

•

The Array Utilities function panels copy, initialize, and clear arrays.

•

Miscellaneous is a class of function panels for miscellaneous Analysis Library functions.

The online help with each panel contains specific information about operating each function
panel.
Hints for Using Analysis Function Panels
With the analysis function panels, you can manipulate scalars and arrays of data interactively.
You will find it helpful to use the Analysis Library function panels in conjunction with the User
Interface Library function panels to view the results of analysis routines. When using the
Analysis Library function panels, remember the following things.
•

The processing speed of the analysis functions is affected by the computer on which you are
running LabWindows/CVI. A numeric coprocessor, especially, increases the speed of
floating-point computations. If you are using an Analysis Library function panel and nothing
seems to happen for an inordinate amount of time, keep the constraints of your hardware in
mind.

•

Many analysis routines for arrays run in place. That is, the input and output data can be
stored in the same array. This is very important to keep in mind when you are processing

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Chapter 3

large amounts of data. Large double-precision arrays consume a lot of memory. If the
results you want do not require that you keep the original array or intermediate arrays of data,
perform analysis operations in place where possible.
•

The Interactive window maintains a record of generated code. If you forget to keep the code
from a function panel, you can cut and paste code between the Interactive and Program
windows.

Reporting Analysis Errors
The functions in the Analysis Library return status information through a return value.
If the return value status is zero after an Analysis Library function call, the function properly
executed with no errors. Otherwise, status is set to the appropriate error value. Error messages
corresponding to the possible status values are listed at the end of this chapter.

Analysis Library Function Reference
This section describes each function in the LabWindows/CVI Analysis Library. The
LabWindows/CVI Analysis Library functions are arranged alphabetically.

Abs1D
int status = Abs1D (double inputArray[], int numberofElements,
double outputArray[]);
Purpose
Finds the absolute value of the inputArray. The function performs the operation in place;
inputArray and outputArray can be the same array.
Parameters
Input

inputArray

double-precision
array

numberofElements integer
Output

outputArray

LabWindows/CVI Standard Libraries

Input array.
Number of elements.

double-precision
array

3-4

Absolute value of input array.

© National Instruments Corporation

Chapter 3

Analysis Library

Return Value
integer

status

Refer to error codes in
Table 3-2.

Add1D
int status = Add1D (double arrayX[], double arrayY[], int numberofElements,
double outputArray[]);
Purpose
Adds one-dimensional (1D) arrays. The function obtains the ith element of the output array by
using the following formula:
zi = xi + yi
The function performs the operation in place; that is, outputArray can be the same array as
either arrayX or arrayY.
Parameters
Input

arrayX

double-precision
array

Input array.

arrayY

double-precision
array

Input array.

numberofElements integer
Output

outputArray

Number of elements to be
added.

double-precision
array

Result array.

integer

Refer to error codes in
Table 3-2.

Return Value
status

Add2D
int status = Add2D (void *arrayX, void *arrayY, int numberofRows,
int numberofColumns, void *outputArray);

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Purpose
Adds two (2D) arrays. The function obtains the (ith, jth) element of the output array by using the
following formula.
z i , j = x i , j + yi , j
The function performs the operation in place; outputArray can be the same array as either
arrayX or arrayY.
Parameters
Input

arrayX

double-precision 2D Input array.
array

arrayY

double-precision 2D Input array.
array

numberofRows

integer

Number of elements in first
dimension.

numberofColumns integer
Output

outputArray

Number of elements in second
dimension.

double-precision 2D Result array.
array

Return Value
integer

status

Refer to error codes in
Table 3-2.

Clear1D
int status = Clear1D (double array[], int numberofElements);
Purpose
Sets the elements of the array to zero.
Parameters
Input

numberofElements integer

Output

array

LabWindows/CVI Standard Libraries

Number of elements in array.

double-precision
array

3-6

Cleared array.

© National Instruments Corporation

Chapter 3

Analysis Library

Return Value
integer

status

Refer to error codes in
Table 3-2.

Copy1D
int status = Copy1D (double inputArray[], int numberofElements,
double outputArray[]);
Purpose
Copies the elements of the inputArray. This function is useful to duplicate arrays for in-place
operations.
Parameters
Input

inputArray

double-precision Input array.
array

numberofElements integer
Output

outputArray

Number of elements in
inputArray.

double-precision Duplicated array.
array

Return Value
status

integer

Refer to error codes in Table 3-2.

CxAdd
int status = CxAdd (double xReal, double xImaginary, double yReal,
double yImaginary, double *outputReal
double*outputImaginary);
Purpose
Adds two complex numbers. The function obtains the resulting complex number by using the
formulas.
zr = xr + yr
zi = xi + yi

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Parameters
Input

Output

xReal

double-precision

Real part of x.

xImaginary

double-precision

Imaginary part of x.

yReal

double-precision

Real part of y.

yImaginary

double-precision

Imaginary part of y.

outputReal

double-precision

Real part of z.

outputImaginary

double-precision

Imaginary part of z.

integer

Refer to error codes in Table 3-2.

Return Value
status

CxAdd1D
int status = CxAdd1D (double arrayXReal[], double arrayXImaginary[],
double arrayYReal[], double arrayYImaginary[],
int numberofElements, double outputArrayReal[],
double outputArrayImaginary[]);
Purpose
Adds two 1D complex arrays. The function obtains the ith element of the resulting complex
array by using the following formulas.
zri = xri + yri
zii = xii + yii
The function performs the operations in place; that is, the input and output complex arrays can be
the same.
Parameters
Input

Output

arrayXReal

double-precision array

Real part of x.

arrayXImaginary

double-precision array

Imaginary part of x.

arrayYReal

double-precision array

Real part of y.

arrayYImaginary

double-precision array

Imaginary part of y.

numberofElements

integer

Number of elements.

outputArrayReal

double-precision array

Real part of z.

outputArrayImaginary double-precision array

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Imaginary part of z.

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Chapter 3

Analysis Library

Return Value
integer

status

Refer to error codes in
Table 3-2.

CxDiv
int status = CxDiv (double xReal, double xImaginary, double yReal, yImaginary,
double *outputReal, double *outputImaginary);
Purpose
Divides two complex numbers. The function obtains the resulting complex number by using the
following formulas.
zr = (xr*yr + xi*yi) / (yr2 + yi2)
zi = (xi*yr - xr*yi ) / (yr2 + yi2)
Parameters
Input

Output

xReal

double-precision

Real part of x.

xImaginary

double-precision

Imaginary part of x.

yReal

double-precision

Real part of y.

yImaginary

double-precision

Imaginary part of y.

outputReal

double-precision

Real part of z.

outputImaginary

double-precision

Imaginary part of z.

integer

Refer to error codes in
Table 3-2.

Return Value
status

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CxDiv1D
int status = CxDiv1D (double arrayXReal[], double arrayXImaginary[],
double arrayYReal[], double arrayYImaginary)[],
int numberofElements, double outputArrayReal[],
double outputArrayImaginary[]);
Purpose
Divides two 1D complex arrays. The function obtains the ith element of the resulting complex
array by using the following formulas.
zri = ( xri ∗ yri + xii ∗ yii ) / ( yri 2 + yii 2 )
zii = ( xii ∗ yri − xri ∗ yii ) / ( yri 2 + yii 2 )
The function performs the operations in place; that is, the input and output complex arrays can be
the same.
Parameters
Input

Output

arrayXReal

double-precision
array

Real part of x.

arrayXImaginary

double-precision
array

Imaginary part of x.

arrayYReal

double-precision
array

Real part of y.

arrayYImaginary

double-precision
array

Imaginary part of y.

numberofElements

integer

Number of elements.

outputArrayReal

double-precision
array

Real part of z.

outputArrayImaginary double-precision
array

Imaginary part of z.

Return Value
status

LabWindows/CVI Standard Libraries

integer

Refer to error codes in
Table 3-2.

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Chapter 3

Analysis Library

CxLinEv1D
int status = CxLinEv1D (double arrayXReal[], double arrayXImaginary[],
int numberofElements, double aReal, double aImaginary,
double bReal, double bImaginary,
double outputArrayReal[],
double outputArrayImaginary[]);
Purpose
Performs a complex linear evaluation of a 1D complex array. The function obtains the ith
element of the resulting complex array by using the following formulas.
yri = ( ar∗ xri − ai∗ xii ) + br
yii = (ar∗ xii + ai∗ xri ) + bi
The function performs the operations in place; that is, the input and output complex arrays can be
the same.
Parameters
Input

Output

arrayXReal

double-precision
array

Real part of x.

arrayXImaginary

double-precision
array

Imaginary part of x.

numberofElements

integer

Number of elements.

aReal

double-precision

Real part of a.

aImaginary

double-precision

Imaginary part of a.

bReal

double-precision

Real part of b.

bImaginary

double-precision

Imaginary part of b.

outputArrayReal

double-precision
array

Real part of y.

outputArrayImaginary double-precision
array

Imaginary part of y.

Return Value
status

© National Instruments Corporation

integer

Refer to error codes in
Table 3-2.

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CxMul
int status = CxMul (double xReal, double xImaginary, double yReal,
double yImaginary, double *outputReal,
double *outputImaginary);
Purpose
Multiplies two complex numbers. The function obtains the resulting complex number by using
the following formulas.
zr = xr*yr - xi*yi
zi = xr*yi + xi*yr
Parameters
Input

Output

xReal

double-precision

Real part of x.

xImaginary

double-precision

Imaginary part of x.

yReal

double-precision

Real part of y.

yImaginary

double-precision

Imaginary part of y.

outputReal

double-precision

Real part of z.

outputImaginary

double-precision

Imaginary part of z.

integer

Refer to error codes in Table 3-2.

Return Value
status

CxMul1D
int status = CxMul1D (double arrayXReal[], double arrayXImaginary[],
double arrayYReal[], double arrayYImaginary[],
int numberofElements, double outputArrayReal[],
double outputArrayImaginary[]);
Purpose
Multiplies two 1D complex arrays. The function obtains the ith element of the resulting complex
array by using the formulas:
zri = xri ∗ yri − xii ∗ yii
zii = xri ∗ yii + xii ∗ yri

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Chapter 3

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The function performs the operations in place; that is, the input and output complex arrays can be
the same.
Parameters
Input

Output

arrayXReal

double-precision
array

Real part of x.

arrayXImaginary

double-precision
array

Imaginary part of x.

arrayYReal

double-precision
array

Real part of y.

arrayYImaginary

double-precision
array

Imaginary part of y.

numberofElements

integer

Number of elements.

outputArrayReal

double-precision
array

Real part of z.

outputArrayImaginary double-precision
array

Imaginary part of z.

Return Value
status

integer

Refer to error codes in
Table 3-2.

CxRecip
int status = CxRecip (double xReal, double xImaginary, double *outputReal,
double *outputImaginary);
Purpose
Finds the reciprocal of a complex number. The function obtains the resulting complex number
by using the following formulas.
yr = xr / (xr2 + xi2)
yi = -xi / (xr2 + xi2)

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Parameters
Input
Output

xReal

double-precision

Real part of x.

xImaginary

double-precision

Imaginary part of x.

outputReal

double-precision

Real part of y.

outputImaginary

double-precision

Imaginary part of y.

integer

Refer to error codes in Table 3-2.

Return Value
status

CxSub
int status = CxSub (double xReal, double xImaginary, double yReal,
double yImaginary, double *outputReal,
double *outputImaginary);
Purpose
Subtracts two complex numbers. The function obtains the resulting complex number by using
the following formulas.
zr = xr - yr
zi = xi - yi
Parameters
Input

Output

xReal

double-precision

Real part of x.

xImaginary

double-precision

Imaginary part of x.

yReal

double-precision

Real part of y.

yImaginary

double-precision

Imaginary part of y.

outputReal

double-precision

Real part of z.

outputImaginary

double-precision

Imaginary part of z.

integer

Refer to error codes in
Table 3-2.

Return Value
status

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CxSub1D
int status = CxSub1D (double arrayXReal[], double arrayXImaginary[],
double arrayYReal[], double arrayYImaginary[],
int numberofElements, double outputArrayReal[],
double outputArrayImaginary[]);
Purpose
Subtracts two 1D complex arrays. The function obtains the ith element of the resulting complex
array by using the following formulas.
zri = xri − yri
zii = xii − yii
The function performs the operations in place; that is, the input and output complex arrays can be
the same.
Parameters
Input

Output

arrayXReal

double-precision
array

Real part of x.

arrayXImaginary

double-precision
array

Imaginary part of x.

arrayYReal

double-precision
array

Real part of y.

arrayYImaginary

double-precision
array

Imaginary part of y.

numberofElements

integer

Number of elements.

outputArrayReal

double-precision
array

Real part of z.

outputArrayImaginary double-precision
array

Imaginary part of z.

Return Value
status

© National Instruments Corporation

integer

Refer to error codes in
Table 3-2.

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Chapter 3

Determinant
int status = Determinant (void *inputMatrix, int matrixSize, double *determinant);
Purpose
Finds the determinant of a matrixSize by matrixSize 2D input matrix.
Parameters
Input

Output

inputMatrix

double-precision 2D Input matrix.
array

matrixSize

integer

Dimension size of input matrix.

determinant

double-precision

Determinant.

Note: The input matrix must be a matrixSize by matrixSize square matrix.
Return Value
status

integer

Refer to error codes in
Table 3-2.

Div1D
int status = Div1D (double arrayX[], double arrayY[], int numberofElements,
double outputArray[]);
Purpose
Divides two 1D arrays. The function obtains the ith element of the output array by using the
following formula.
zi = xi / yi
The function performs the operation in place; that is, outputArray can be the same array as
either arrayX or arrayY.

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Parameters
Input

Output

arrayX

double-precision
array

Input array.

arrayY

double-precision
array

Input array.

numberofElements

integer

Number of elements to be divided.

outputArray

double-precision
array

Result array.

integer

Refer to error codes in Table 3-2.

Return Value
status

Div2D
int status = Div2D (void *arrayX, void *arrayY, int numberofRows,
int numberofColumns, void *outputArray);
Purpose
Divides two 2D arrays. The function obtains the (ith, jth) element of the output array by using
the following formula.
zi, j = xi, j / yi, j
The function performs the operation in place; that is, outputArray can be the same array as
either arrayX or arrayY.
Parameters
Input

arrayX

double-precision 2D Input array.
array

arrayY

double-precision 2D Input array.
array

numberofRows

integer

Number of elements in first
dimension.

numberofColumns integer
Output

outputArray

© National Instruments Corporation

Number of elements in second
dimension.

double-precision 2D Result array.
array

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Chapter 3

Return Value
integer

status

Refer to error codes in
Table 3-2.

DotProduct
int status = DotProduct (double vectorX[], double vectorY[],
int numberofElements,
double *dotProduct);
Purpose
Computes the dot product of the vectorX and vectorY input arrays. The function obtains the dot
product by using the following formula:
n −1

dotproduct = x • y = ∑ xi ∗ yi
i=0

Parameters
Input

vectorX

double-precision
array

Input vector.

vectorY

double-precision
array

Input vector.

numberofElements integer
Output

dotProduct

Number of elements.

double-precision

Dot product.

integer

Refer to error codes in
Table 3-2.

Return Value
status

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GetAnalysisErrorString
char *message = GetAnalysisErrorString (int errorNum)
Purpose
Converts the error number returned by an Analysis Library function into a meaningful error
message.
Parameters
Input

errorNum

integer

Status returned by an
Analysis function.

string

Explanation of error.

Return Value
message

Histogram
int status = Histogram (double inputArray[], int numberofElements, double base,
double top, int histogramArray[], double axisArray[],
int intervals);
Purpose
Computes the histogram of the inputArray. The histogram is obtained by counting the number
of times that the elements in the input array fall in the ith interval. Let

∆ x = (xTop - xBase) / intervals
yx,i =

{10

if i∆x ≤ x - xBase < (i + 1)∆x
otherwise

The ith element of the histogram is:
n −1

histi = ∑ y( x j , i )
j =0

The values of the histogram axis are the mid-point values of the intervals:
axisi = i∆x + ∆x / 2 + xBase

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Parameters
Input

inputArray

double-precision
array

numberofElements integer

Input array.
Number of elements in
Input Array.

Output

base

double-precision

Lower range.

top

double-precision

Upper range.

intervals

integer

Number of intervals.

histogramArray

integer array

Histogram of input Array.

axisArray

double-precision
array

Histogram axis array.

integer

Refer to error codes in
Table 3-2.

Return Value
status

InvMatrix
int status = InvMatrix (void *inputMatrix, int matrixSize, void *outputMatrix);
Purpose
Finds the inverse matrix of an input matrix. The operation can be performed in place; that is,
inputMatrix and outputMatrix can be the same matrices.
Parameters
Input

Output

inputMatrix

double-precision 2D Input matrix.
array

matrixSize

integer

outputMatrix

double-precision 2D Inverse matrix.
array

Dimension of matrix.

Note: The input matrix must be a matrixSize by matrixSize square matrix.

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Return Value
integer

status

Refer to error codes in n
Table 3-2.

LinEv1D
int status = LinEv1D (double inputArray[], int numberofElements,
double multiplier, double additiveConstant,
double outputArray[]);
Purpose
Performs a linear evaluation of a 1D array. The function obtains the ith element of the output
array by using the following formula.
yi = a∗ xi + b
The operation can be performed in place; that is, inputArray and outputArray can be the same
array.
Parameters
Input

inputArray

double-precision
array

numberofElements integer
double-precision
multiplier
Output

Input array.
Number of elements.
Multiplicative constant.

additiveConstant

double-precision

Additive constant.

outputArray

double-precision
array

Linearly evaluated array.

integer

Refer to error codes in
Table 3-2.

Return Value
status

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Chapter 3

LinEv2D
int status = LinEv2D (void *inputArray, int numberofRows, int numberofColumns,
double multiplier, double additiveConstant,
void *outputArray);
Purpose
Performs a linear evaluation of a 2D array. The function obtains the (ith, jth) element of the
output array by using the following formula.
yi,j = a* xi,j + b
The function performs the operation in place; that is, inputArray and outputArray can be the
same array.
Parameters
Input

inputArray

double-precision 2D Input array.
array

numberofRows

integer

Number of elements in first
dimension.

numberofColumns integer

Output

Number of elements in second
dimension.

multiplier

double-precision

Multiplicative constant.

additiveConstant

double-precision

Additive constant.

outputArray

double-precision 2D Linearly evaluated array.
array

Return Value
status

LabWindows/CVI Standard Libraries

integer

Refer to error codes in
Table 3-2.

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Chapter 3

Analysis Library

MatrixMul
int status = MatrixMul (void *matrixX, void *matrixY, int #ofRowsInX,
int cols/rowsInX/Y, int #ofColumnsInY,
void *outputMatrix);
Purpose
Multiplies two 2D input matrices. The function obtains the (ith, jth) element of the output matrix
by using the following formula.
k −1

zi , j = ∑ x i , p ∗ y p , j
p= 0

Parameters
Input

Output

matrixX

double-precision 2D matrixX input matrix.
array

matrixY

double-precision 2D matrixY input matrix.
array

#ofRowsInX

integer

First dimension of matrixX.

cols/rowsInX/Y

integer

Second dimension of matrixX.;
first dimension of matrixY.

#ofColumnsInY

integer

Second dimension of matrixY.

outputMatrix

double-precision 2D Output matrix.
array

Return Value
integer

status

Refer to error codes in
Table 3-2.

Parameter Discussion
Note: Be sure to use the correct array sizes. The following array sizes must be met:
•

matrixX must be (#ofRowsInX by cols/rowsInX/Y).

•

matrixY must be (cols/rowsInX/Y by #ofColumnsInY).

•

outputMatrix must be (#ofRowsInX by #ofColumnsInY).

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Chapter 3

MaxMin1D
int status = MaxMin1D (double inputArray[], int numberofElements,
double *maximumValue, int *maximumIndex,
double *minimumValue, int *minimumIndex);
Purpose
Finds the maximum and minimum values in the input array, as well as the respective indices of
the first occurrence of the maximum and minimum values.
Parameters
Input

inputArray

double-precision
array

numberofElements integer
Output

Input array.
Number of elements.

maximumValue

double-precision

Maximum value.

maximumIndex

integer

Index of maximumValue in
inputArray.

minimumValue

double-precision

Minimum value.

minimumIndex

integer

Index of minimumValue in
inputArray.

integer

Refer to error codes in
Table 3-2.

Return Value
status

MaxMin2D
int status = MaxMin2D (void *inputArray, int numberofRows,
int numberofColumns, double *maximumValue,
int *maximumRowIndex, int *maximumColumnIndex,
double *minimumValue, int *minimumRowIndex,
int *minimumColumnIndex);
Purpose
Finds the maximum and the minimum values in the 2D input array, as well as the respective
indices of the first occurrence of the maximum and minimum values. The inputArray is
scanned by rows.

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Chapter 3

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Parameters
Input

Output

inputArray

double-precision
2D array

Input array.

numberofRows

integer

Number of elements in first
dimension of inputArray.

numberofColumns

integer

Number of elements in second
dimension of inputArray.

maximumValue

double-precision

Maximum value.

maximumRowIndex

integer

Index of maximumValue in
inputArray array (first
dimension).

maximumColumnIndex

integer

Index of maximumValue in
inputArray (second
dimension).

minimumValue

double-precision

Minimum value.

minimumRowIndex

integer

Index of minimumValue in
inputArray (first dimension).

minimumColumnIndex

integer

Index of minimumValue in
inputArray array (second
dimension).

Return Value
integer

status

Refer to error codes in
Table 3-2.

Mean
int status = Mean (double inputArray[], int numberofElements, double *mean);
Purpose
Compute the mean (average) value of the input array. The function uses the following formula
to find the mean.
n −1

meanval = ∑ x i / n
i=0

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Chapter 3

Parameters
Input

inputArray

double-precision
array

numberofElements integer
Output

mean

Input array.
Number of elements in
inputArray.

double-precision

Mean value.

integer

Refer to error codes in
Table 3-2.

Return Value
status

Mul1D
int status = Mul1D (double arrayX[], double arrayY[], int numberofElements,
double outputArray[]);
Purpose
Multiplies two 1D arrays. The function obtains the ith element of the output array by using the
following formula.
zi = xi ∗ yi
The function performs the operation in place; that is, outputArray can be the same array as
either arrayX or arrayY.
Parameters
Input

arrayX

double-precision
array

Input array.

arrayY

double-precision
array

Input array.

numberofElements integer
Output

outputArray

LabWindows/CVI Standard Libraries

Number of elements to be
multiplied.

double-precision
array

3-26

Result array.

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Chapter 3

Analysis Library

Return Value
integer

status

Refer to error codes in
Table 3-2.

Mul2D
int status = Mul2D (void *arrayX, void *arrayY, int numberofRows,
int numberofColumns, void *outputArray);
Purpose
Multiplies two 2D arrays. The function obtains the (ith, jth) element of the output array by using
the following formula.
z i , j = x i, j * yi , j
The function performs the operation in place; that is, outputArray can be the same array as
either arrayX or arrayY.
Parameters
Input

arrayX

double-precision 2D Input array.
array

arrayY

double-precision 2D Input array.
array

numberofRows

integer

Number of elements in first
dimension.

numberofColumns integer
Output

outputArray

Number of elements in second
dimension.

double-precision 2D Result array.
array

Return Value
status

© National Instruments Corporation

integer

Refer to error codes in
Table 3-2.

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Chapter 3

Neg1D
int status = Neg1D (double inputArray[], int numberofElements,
double outputArray[]);
Purpose
Negates the elements of the input array. The function performs the operation in place; that is,
inputArray and outputArray can be the same array.
Parameters
Input

Output

inputArray

double-precision Input array.
array

numberofElements

integer

outputArray

double-precision Negated values of the inputArray.
array

Number of elements.

Return Value
integer

status

Refer to error codes in Table 3-2.

Set1D
int status = Set1D (double array[], int numberofElements, double setValue);
Purpose
Sets the elements of the input array to a constant value.
Parameters
Input
Output

numberofElements

integer

Number of elements in array.

setValue

double-precision

Constant value.

array

double-precision
array

Result array (set to the value
of setValue).

integer

Refer to error codes in Table 3-2.

Return Value
status

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Chapter 3

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Sort
int status = Sort (double inputArray[], int numberofElements, int direction,
double outputArray[]);
Purpose
Sorts the input array in ascending or descending order. The function performs the operation in
place; that is, inputArray and outputArray can be the same array.
Parameters
Input

inputArray

double-precision
array

numberofElements integer
direction

Input array.
Number of elements to be
sorted.

integer

0: ascending.
Non-zero: descending.

Output

outputArray

double-precision
array

Sorted array.

integer

Refer to error codes in
Table 3-2.

Return Value
status

StdDev
int status = StdDev (double inputArray[], int numberofElements, double *mean,
double *standardDeviation);
Purpose
Computes the standard deviation and the mean (average) values of the input array. The formulas
used to find the mean and the standard deviation are as follows.
n −1

meanval = ∑ x i / n
i=0

n-1

sDev =

∑

[x i - ave]2 / n

i=0

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Chapter 3

Parameters
Input

inputArray

double-precision
array

numberofElements integer
Output

Input array.
Number of elements in
inputArray.

mean

double-precision

Mean value.

standardDeviation

double-precision

Standard deviation.

integer

Refer to error codes in
Table 3-2.

Return Value
status

Sub1D
int status = Sub1D (double arrayX[], double arrayY[], int numberofElements,
double outputArray[]);
Purpose
Subtracts two 1D arrays. The function obtains the ith element of the output array by using the
following formula:
zi = xi − yi
The operation can be performed in place; that is, outputArray can be in place of either arrayX
or arrayY.
Parameters
Input

arrayX

double-precision
array

Input array.

arrayY

double-precision
array

Input array.

numberofElements integer
Output

outputArray

LabWindows/CVI Standard Libraries

Number of elements to be
subtracted.

double-precision
array

3-30

Result array.

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Chapter 3

Analysis Library

Return Value
integer

status

Refer to error codes in
Table 3-2.

Sub2D
int status = Sub2D (void *arrayX, void *arrayY, int numberofRows,
int numberofColumns, void *outputArray);
Purpose
Subtracts two 2D arrays. The function obtains the (ith, jth) element of the output array by using
the formula:
z i , j = x i , j − yi , j
The function performs the operation in place; that is, outputArray can be in place of either
arrayX or arrayY.
Parameters
Input

arrayX

double-precision 2D Input array.
array

arrayY

double-precision 2D Input array.
array

numberofRows

integer

Number of elements in first
dimension.

numberofColumns integer
Output

outputArray

Number of elements in second
dimension.

double-precision 2D Result array.
array

Return Value
status

© National Instruments Corporation

integer

Refer to error codes in
Table 3-2.

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Chapter 3

Subset1D
int status = Subset1D (double inputArray[], int numberofElements, int index,
int length, double outputArray[]);
Purpose
Extracts a subset of the inputArray input array containing the number of elements specified by
the length and starting at the index element.
Parameters
Input

inputArray

double-precision
array

numberofElements integer

Output

Input array.
Number of elements in
inputArray.

index

integer

Initial index for the subset.

length

integer

Number of elements copied to
the subset.

outputArray

double-precision
array

Subset array.

integer

Refer to error codes in
Table 3-2.

Return Value
status

ToPolar
int status = ToPolar (double xReal, double yImaginary, double *magnitude,
double *phaseRadians);
Purpose
Converts the rectangular coordinates (xReal, yImaginary) to polar coordinates (magnitude,
phaseRadians). The formulas used to obtain the polar coordinates are as follows.
mag =

x2 + y2

phase = arctan (y/x)
The phaseRadians value is in the range of [ -π to π ]

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Chapter 3

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Parameters
Input
Output

xReal

double-precision

X coordinate.

yImaginary

double-precision

X coordinate.

magnitude

double-precision

Magnitude.

phaseRadians

double-precision

Phase (in radians).

integer

Refer to error codes in
Table 3-2.

Return Value
status

ToPolar1D
int status = ToPolar1D (double arrayXReal[], double arrayYImaginary[],
int numberofElements, double magnitude[],
double phaseRadians[]);
Purpose
Converts the set of rectangular coordinate points (arrayXReal, arrayYImaginary) to a set of
polar coordinate points (magnitude, phaseRadians). The function obtains the ith element of the
polar coordinate set by using the following formulas.
magi =

xi 2 + yi 2

phasei = arctan yi / xi
The phaseRadians value is in the range of [ -π to π ].
The function performs the operations in place; that is, arrayXReal and magnitude, and
arrayYImaginary and phaseRadians, can be the same arrays, respectively.

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Chapter 3

Parameters
Input

arrayXReal

double-precision
array

X coordinate.

arrayYImaginary

double-precision
array

Y coordinate.

numberofElements integer
Output

Number of elements.

magnitude

double-precision
array

Magnitude.

phaseRadians

double-precision
array

Phase (in radians).

integer

Refer to error codes in
Table 3-2.

Return Value
status

ToRect
int status = ToRect (double magnitude, double phaseRadians, double *xReal,
double *yImaginary);
Purpose
Converts the polar coordinates (magnitude, phaseRadians) to rectangular coordinates (xReal,
yImaginary). The formulas used to obtain the rectangular coordinates are as follows.
x = mag * cos(phase)
y = mag * sin(phase)
Parameters
Input
Output

magnitude

double-precision

Magnitude.

phaseRadians

double-precision

Phase (in radians).

xReal

double-precision

X coordinate.

yImaginary

double-precision

Y coordinate.

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Chapter 3

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Return Value
integer

status

Refer to error codes in
Table 3-2.

ToRect1D
int status = ToRect1D (double magnitude[], double phaseRadians[],
int numberofElements, double outputArrayReal[],
double outputArrayImaginary[]);
Purpose
Converts the set of polar coordinate points (magnitude, phaseRadians) to a set of rectangular
coordinate points (outputArrayReal, outputArrayImaginary). The function obtains the ith
element of the rectangular set by using the following formulas.
xi = magi ∗ cos( phasei )
yi = magi ∗sin( phasei )
The function performs the operations in place; that is, outputArrayReal and magnitude, and
outputArrayImaginary and phaseRadians, can be the same arrays, respectively.
Parameters
Input

Output

magnitude

double-precision
array

Magnitude.

phaseRadians

double-precision
array

Phase (in radians).

numberofElements

integer

Number of elements.

outputArrayReal

double-precision
array

X coordinate.

outputArrayImaginary double-precision
array

Y coordinate.

Return Value
status

© National Instruments Corporation

integer

Refer to error codes in
Table 3-2.

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Chapter 3

Transpose
int status = Transpose (void *inputMatrix, int numberofRows,
int numberofColumns, void *outputMatrix);
Purpose
Finds the transpose of a 2D input matrix. The (ith, jth) element of the resulting matrix uses the
formula:
yi,j = xi,j
Parameters
Input

inputMatrix

double-precision 2D Input matrix.
array

numberofRows

integer

Size of first dimension.

numberofColumns integer
Output

outputMatrix

Size of second dimension.

double-precision 2D Transpose matrix.
array

Note: If the input matrix is dimensioned (numberofRows by numberofColumns), then the
output matrix must be dimensioned (numberofColumns by numberofRows).
Return Value
status

LabWindows/CVI Standard Libraries

integer

Refer to error codes in
Table 3-2.

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Chapter 3

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Error Conditions
If an error condition occurs during a call to any of the functions in the LabWindows/CVI
Analysis Library, the status return value contains the error code. This code is a value that
specifies the type of error that occurred. The currently defined error codes and their associated
meanings are given in Table 3-2.
Table 3-2. Analysis Library Error Codes
Symbolic Name

Code

Error Message

BaseGETopAnlysErr

-20101

Base must be less than Top.

DivByZeroAnlysErr

-20060

Divide by zero err.

IndexLengthAnlysErr

-20018

The following condition must be met:
0 ≤ (index + length) < samples.

NoAnlysErr

0

No error; the call was successful.

OutOfMemAnlysErr

-20001

There is not enough space left to perform the specified
routine.

SamplesGEZeroAnlysErr

-20004

The number of samples must be greater than or equal to
zero.

SamplesGTZeroAnlysErr

-20003

The number of samples must be greater than zero.

SingularMatrixAnlysErr

-20041

The input matrix is singular. The system of equations
cannot be solved.

© National Instruments Corporation

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LabWindows/CVI Standard Libraries

Chapter 4
GPIB/GPIB-488.2 Library
This describes the NI-488 and NI-488.2 functions in the LabWindows/CVI GPIB Library, as
well as the Device Manager functions in LabWindows/CVI. The GPIB Library Function
Overview section contains general information about the GPIB Library functions and panels, the
GPIB DLL, and guidelines and restrictions you should know when using the GPIB Library.
Detailed descriptions of the NI-488 and NI-488.2 functions can be found in your NI-488.2
function reference manual. The GPIB Function Reference section contains an alphabetical list of
descriptions for the Device Manager functions, the callback installation functions, and the
functions for returning the thread-specific status variables.

GPIB Library Function Overview
This section describes the functions in the LabWindows/CVI GPIB Library. These functions are
arranged alphabetically according to their names in C. For detailed function descriptions, refer to
the NI-488.2 function reference manual that accompanied your GPIB interface board.

GPIB Functions Library Function Panels
The GPIB Functions Library function panels are grouped in a tree structure according to the
types of operations performed. The GPIB Functions Library function tree is in Table 4-1.
The first- and second-level bold headings in the function tree are names of the function classes.
Function classes are groups of related function panels. The third-level headings in plain text are
the names of individual function panels. Each GPIB function panel generates a GPIB function
call. The actual function names are in bold italics in columns to the right.

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GPIB/GPIB-488.2 Library

Chapter 4

Table 4-1. The GPIB Functions Library Function Tree
GPIB/GPIB-488.2 Library
Open/Close
Open Device
Close Device
Close Instrument Devices
Find Board/Device
Find Unused Device
Offline/Online
Configuration
Change Primary Address
Change Secondary Address
Change Access Board
Change Time Out Limit
Set EOS Character
Enable/Disable END
Enable/Disable DMA
System Control
Change Config Parameter
Get Config Parameter
I/O
Read
Read Asynchronously
Read to File
Write
Write Asynchronously
Write from File
Stop Asynchronous I/O
Device Control
Get Serial Poll Byte
Clear Device
Trigger device
Check for Listeners
Wait for Event (Dev)
Go to Local (Dev)
Parallel Poll Cfg (Dev)
Pass Control

OpenDev
CloseDev
CloseInstrDevs
ibfind
ibdev
ibonl
ibpad
ibsad
ibbna
ibtmo
ibeos
ibeot
ibdma
ibrsc
ibconfig
ibask
ibrd
ibrda
ibrdf
ibwrt
ibwrta
ibwrtf
ibstop
ibrsp
ibclr
ibtrg
ibln
ibwait
ibloc
ibppc
ibpct
(continues)

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Chapter 4

GPIB/GPIB-488.2 Library

Table 4-1. The GPIB Functions Library Function Tree (Continued)
Bus Control
Send Interface Clear
Become Active Controller
Go to Standby
Set/Clear Remote Enable
Send Commands
Send Commands (Async)
Parallel Poll
Read Control Lines
Board Control
Wait for Board Event
Dequeue Board Event
Set UNIX Signal Request
Go to Local Mode
Parallel Poll Configuration
Request Service
Set/Clear IST
Write to Board Key
Read from Board Key
Callbacks (Windows only)
Install Synchronous Callback
Install Asynchronous Callback
Thread-Specific Status
Get Ibsta for Thread
Get Iberr for Thread
Get Ibcnt for Thread
Get Ibcntl for Thread
GPIB-488.2 Functions
Device I/O
Send
Send to Multiple Devices
Receive
Trigger and Clear
Trigger Device
Trigger Multile Devices
Clear Device
Clear Multiple Devices

ibsic
ibcac
ibgts
ibsre
ibcmd
ibcmda
ibrpp
iblines
ibwait
ibevent
ibsignal
ibloc
ibppc
ibrsv
ibist
ibwrtkey
ibrdkey
ibInstallCallback
ibNotify
ThreadIbsta
ThreadIberr
ThreadIbcnt
ThreadIbcntl

Send
SendList
Receive
Trigger
TriggerList
DevClear
DevClearList
(continues)

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GPIB/GPIB-488.2 Library

Chapter 4

Table 4-1. The GPIB Functions Library Function Tree (Continued)
SRQ and Serial Polls
Test SRQ line
Wait for SRQ
Find Requesting Device
Read Status Byte
Serial Poll All Devices
Parallel Polls
Parallel Poll
Parallel Poll Config
Parallel Poll Unconfig
Remote/Local
Enable Remote Operation
Enable Local Operation
Set remote with Lockout
Send Local Lockout
System Control
Reset System
Send Interface Clear
Conduct Self-Tests
Find All Listeners
Pass Control
Low-Level I/O
Send Commands
Setup for Sending
Send Data Bytes
Setup for Receiving
Receive Response Message

TestSRQ
WaitSRQ
FindRQS
ReadStatusByte
AllSpoll
PPoll
PPollConfig
PPollUnconfig
EnableRemote
EnableLocal
SetRWLS
SendLLO
ResetSys
SendlFC
TestSys
FinsLstn
PassControl
SendCmds
SendSetup
SendDataBytes
ReceiveSetup
RcvRespMsg

The classes and subclasses in the tree are described here.
•

The Open/Close function panels open and close GPIB boards and devices.

•

The Configuration function panels alter configuration parameters that were set during
installation of the GPIB handler or during the execution of previous program statements.

•

The I/O function panels read and write data over the GPIB. These functions can be used at
either the board or the device level.

•

The Device Control function panels provide high-level, commonly used GPIB services for
instrument control applications.

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Chapter 4

GPIB/GPIB-488.2 Library

•

The Bus Control function panels provide low-level control of the GPIB bus.

•

The Board Control function panels provide low-level control of the GPIB board. These
functions are normally used when the GPIB board is not controller-in-charge.

•

The Callbacks function panels install callback functions that are invoked when certain GPIB
events occur. The functions in this class are available only under Windows. Under UNIX,
you can use the ibsgnl function.

•

The Thread-Specific Status function panels return the value of the thread-specific GPIB
status variables for the current thread. The functions in this class are needed only for
multithreaded applications and are available only on Windows 95 and NT.

•

The GPIB 488.2 Functions function panels directly adhere to the IEEE-488.2 standard for
communicating with and controlling GPIB devices.
− The Device I/O function panels read data from, and write data to, devices on the GPIB.
− The Trigger and Clear function panels trigger and clear GPIB devices.
− The SRQ and Serial Polls function panels handle service requests and perform
serial polls.
− The Parallel Polls function panels conduct parallel polls and configure devices to
respond to them.
− The Remote/Local function panels enable and disable operation of devices remotely via
the GPIB or locally via the front panel of the device.
− The System Control function panels perform system-wide functions, obtain system-wide
status information, and pass system control to other devices.
− The Low-Level I/O function panels perform I/O functions at a lower-level than the
function panels in the other classes.

GPIB Library Concepts
This section contains general information about the GPIB Library, the GPIB device driver,
guidelines and restrictions you should know when using the GPIB Library, and descriptions of
the types of GPIB functions that the GPIB Library contains.

GPIB Libraries and the GPIB Dynamic Link Library/Device Driver
LabWindows/CVI for Windows uses National Instruments standard Windows GPIB.DLL.
LabWindows/CVI for Sun uses the standard Sun Solaris-installed GPIB device drivers. These

© National Instruments Corporation

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GPIB/GPIB-488.2 Library

Chapter 4

drivers are packaged with your GPIB interface board and are not included with
LabWindows/CVI. LabWindows/CVI does not require any special procedures for installing and
using the device driver. Follow the directions outlined in your board documentation.
You can use a utility program called IBCONF, included with your GPIB software, to specify
configuration parameters for devices on the GPIB. If your device has special configuration
parameters, such as a secondary address or a special termination character, you can specify these
using IBCONF. When you are using the LabWindows/CVI GPIB Library function panels,
parameters that you specified using IBCONF are still in effect. You can also modify
configuration parameters directly from one of the LabWindows/CVI configuration function
panels, or from your program.
If you are using a LabWindows/CVI Instrument Library module, you do not need to make any
changes using IBCONF. The module takes into account any special configuration requirements
for the instrument controlled by the module. If special parameters must be specified, the module
sets them programmatically.

Guidelines and Restrictions for Using the GPIB Libraries
Follow these guidelines when using the GPIB Libraries:
•

Before performing any other operations, open the device. You must use either the
OpenDev, the ibfind, or the ibdev function. Instrument modules must use the
OpenDev function. When you open a device, an integer value representing a device
descriptor is returned. All subsequent operations that involve a particular device require that
you specify this device descriptor.

•

If OpenDev is used, the CloseDev function should be used to close the device at the end
of the program.

•

Each GPIB Library function panel has three global controls labeled Status, Error, and Count.
These controls show the values of the GPIB status (ibsta), error (iberr) and byte count
(ibcntl) variables.
–

The Status control displays in hexadecimal format. The help information for Status
explains the meaning of each bit in the status word. If the most significant bit is set, a
GPIB error has occurred.

–

When an error occurs, the Error control displays an error number. The help information
for Error describes the type of error associated with each error number.

–

Count displays the number of bytes transferred over the GPIB during the most recent bus
transfer.

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Note: When writing instrument modules, you must use the Device Manager functions
(OpenDev and CloseDev) instead of ibfind or ibdev. You must also use the
Device Manager functions in application programs that make calls to instrument
modules. The Device Manager functions allow instrument modules to open devices
without specific device names, thereby preventing device name conflicts. They also
help the LabWindows/CVI interactive program ensure that devices are closed when no
longer needed.

Device and Board Functions
Device functions are high-level functions that execute command sequences to handle bus
management operations required by activities such as reading from and writing to devices or
polling them for status. Device functions access a specific device and take care of the addressing
and bus management protocol for that device. Because they execute automatically, you do not
need to know any GPIB protocol or bus management details. A descriptor of the accessed device
is one of the arguments of the function.
In contrast, board functions are low-level functions that perform rudimentary GPIB operations.
They are necessary because high-level functions may not always meet the requirements of
applications. In such cases, low-level functions offer the flexibility to meet your application
needs.
Board functions access the GPIB interface board directly and require you to do the addressing
and bus management protocol for the bus. A descriptor of the accessed board is one of the
arguments of the function.

Automatic Serial Polling
Automatic Serial Polling relieves you of the burden of sorting out occurrences of SRQ and status
bytes of a device you can enable. To enable Automatic Serial Polling (or Autopolling), use the
configuration utility, IBCONF, or the configuration function, ibconfig. If you enable
Autopolling, the handler automatically conducts serial polls when SRQ is asserted.
As part of the Autopoll procedure, the handler stores each positive serial poll response in a queue
associated with each device. A positive response has the RQS or hex 40 bit set in the device
status byte. Queues are necessary because some devices can send multiple positive status bytes
back-to-back. When a positive response from a device is received, the RQS bit of its status word
(ibsta) is set. The polling continues until SRQ is unasserted or an error condition is detected.
If the handler cannot locate the device requesting service (no known device responds positively
to the poll) or if SRQ becomes stuck on (because of a faulty instrument or cable), a GPIB system
error exists that will interfere with the proper evaluation of the RQS bit in the status words of
devices. The error ESRQ is reported to you when you issue an ibwait call with the RQS bit

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included in the wait mask. Aside from the difficulty caused by ESRQ in waiting for RQS, the
error will have no detrimental effects on other GPIB operations.
If you call the serial poll function ibrsp and have received one or more responses previously
via the automatic serial poll feature, the ibrsp function returns the first queued response. Other
responses are read in FIFO (first-in-first-out) fashion. If the RQS bit of the status word is not set
when you call ibrsp, the function conducts a serial poll and returns whatever response it
receives.
If your application requires that requests for service be noticed, call the ibrsp function
whenever the RQS bit appears in the status word. A serial poll response queue of a device can
overflow with old status bytes when you neglect to call ibrsp. ibrsp returns the error
condition ESTB when status bytes have been discarded because the queue is full. If your
application has no interest in SRQ or status bytes, you can ignore the occurrence of the automatic
polls.
Note: If the RQS bit of the device status word is still set after you call ibrsp, the response
byte queue has at least one more response byte remaining. You should call ibrsp
until RQS is cleared to gather all stored response bytes and to guard against queue
overflow.
Autopolling Compatibility
You cannot detect the SRQI bit in device status words (ibsta) if you enable Autopolling. The
goal of Autopolling is to remove the SRQ from the IEEE 488 bus, thus preventing visibility of
the SRQI bit in status words for both board calls and device calls. If you choose to look for
SRQI in your program, you must disable Autopolling.
Board functions are also incompatible with Autopolling. The handler disables Autopolling
whenever you make a board call, and re-enables it at the end of a subsequent device call.

Hardware Interrupts and Autopolling
If you have disabled the interrupts of the GPIB interface board via IBCONF or the ibconfig
function, the handler detects SRQ only during calls to the handler, and Autopolling can occur
only at the following events.
• During a device ibwait for RQS,
• Immediately after a device function has completed and is about to return to the application
program.
If you have enabled hardware interrupts, the handler can respond to SRQI interrupts and perform
Autopolling even when the handler is not performing a function. However, the handler will not
conduct an Autopoll if any of the following conditions exist.

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• The last GPIB call was a board call. Autopolling is re-instated after a subsequent device call.
• GPIB I/O is in progress. In particular, during asynchronous GPIB I/O, autopolling will not
occur until the asynchronous I/O has completed.
• The "stuck SRQ" condition exists.
• Autopolling has been disabled by IBCONF or by ibconfig.

Read and Write Termination
The IEEE 488 specification defines two methods of identifying the last byte of device-dependent
(data) messages. The two methods permit a Talker to send data messages of any length without
the Listener(s) knowing in advance the number of bytes in the transmission. The two methods
are as follows.
•

END message. The Talker asserts the EOI (End Or Identify) signal simultaneously with
transmission of the last data byte. By design, the Listener stops reading when it detects a
data message accompanied by EOI, regardless of the value of the byte.

•

End-of-string (EOS) character. The Talker uses a special character at the end of its data
string. By prior arrangement, the Listener stops receiving data when it detects that character.
You can use either a 7-bit ASCII character or a full 8-bit binary byte.

You can use these methods individually or in combination. However, the Listener must be
properly configured to unambiguously detect the end of a transmission.
Using the configuration program, you can accommodate all permissible forms of read and write
termination. (You cannot force the handler to ignore END on read operations.) The default
configuration settings for read and write termination can also be changed at run time using the
ibeos and ibeot functions.

Timeouts
A timeout mechanism regulates the GPIB routines that transfer command sequences or data
messages. A default timeout period of 10 sec is preconfigured in the handler; thus, all I/O must
complete within that period to avoid a timeout error. The default timeout value can be changed
with the IBCONF utility. In addition, you can use the NI-488 board function call ibtmo to
programmatically alter the timeout period.
Regardless of the I/O and Wait timeout period, a much shorter timeout is enforced for responses
to serial polls. This shorter timeout period takes effect whenever a serial poll is conducted.
Because devices normally respond quickly to polls, there is no need to wait the relatively lengthy
I/O timeout period for a nonresponsive device.

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Global Variables for the GPIB Library
The following global variables are used by the GPIB Library and the GPIB-488.2 Library:
•

Status Word (ibsta)

•

Error (ibcnt, ibcntl)

These variables are updated after each NI-488 or NI-488.2 routine to reflect the status of the
device or board just accessed. Refer to your NI-488.2 user manual for detailed information on
the GPIB global variables.

Different Levels of Functionality Depending on Platform and GPIB Board
In general, the GPIB library is same for all platforms and GPIB boards. There are, however,
some exceptions, most notably relating to SRQ notification, support for multithreading, and
limitations on transfer size. These particular issues are discussed later in this chapter. This
section explains the various categories of GPIB support.
Windows 95
There are two kinds of GPIB support for Windows 95. The “native 32-bit” driver and the
“compatibility” driver. You can see which one you have installed on your system by running the
GPIB Information program in your GPIB Software group and noting the name of the driver.
Driver Name

Description

NI-488.2M

Native 32-bit driver.

NI-488.2

Compatibility driver.

Native 32-Bit Driver
The native 32-bit driver is a 32-bit device driver written specifically for Windows 95. It is
supported on the following boards.
•

AT-GPIB/TNT

•

AT-GPIB/TNT+

•

AT-GPIB/TNT (PnP)

•

PCI-GPIB

•

PCMCIA-GPIB

•

PCMCIA-GPIB+

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If you want to use GPIB under Windows 95 and you have an older board, it is recommended that
you upgrade to one of the boards in this list.
Compatibility Driver
The compatibility driver is a 32-to-16-bit thunking DLL that you can use with the Windows 3.1
GPIB driver under Windows 95. All GPIB boards are supported by the compatibility driver. The
compatibility driver has several limitations. In particular, it does not support multithreading and
transfers are limited to 64k bytes.
Windows NT
The GPIB driver for Windows NT is a native 32-bit driver written specifically for Windows NT.
Version 1.0 supports the following boards:
•

AT-GPIB

•

AT-GPIB/TNT

Version 1.2, due to be released in the second half of 1996, will add support for the PCI-GPIB and
PCMCIA-GPIB.

Limitations on Transfer Size
There are no limitations on transfer size except for the compatibility driver under Windows 95.
The compatibility driver is limited to 64 KB transfers.

Multithreading
If you are using multithreading in an external compiler, you can call GPIB functions from more
than one thread at the same time under Windows NT or under Windows 95 with the native 32-bit
driver. In order to be truly multithreaded safe, you must use on of the following versions of the
GPIB driver.
•

For Windows 95: Version 1.1 or later.

•

For Windows NT: Version 1.2 or later.

Although previous versions of the drivers support multithreading, they do not support the
ThreadIbsta, ThreadIberr, ThreadIbcnt, or ThreadIbcntl functions. You need
these functions to obtain thread-specific status values when calling GPIB functions from more
than one thread. The global status variables ibsta, iberr, ibcnt, and ibcntl, are not
reliable in this case because they are maintained on a per process basis.

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Notification of SRQ and Other GPIB Events
Synchronous Callbacks
Under Windows 3.1, you can use ibInstallCallback to specify a function to be called
when an SRQ is asserted on the GPIB or when an asynchronous I/O operation has completed. It
is a board-level function only.
The same functionality exists on Windows 95 when you are using the compatibility driver.
If you are using Windows NT or the native 32-bit driver for Windows 95, you can use
ibInstallCallback to specify functions to be invoked on the occurrence of any board-level
or device-level condition on which you can wait using the ibwait function.
Callback functions installed with ibInstallCallback are synchronous callbacks, that is,
they are invoked only when LabWindows/CVI is processing events. (LabWindows/CVI
processes events when you call ProcessSystemEvents or GetUserEvent, or when
RunUserInterface is active and you are not in a callback function.) Consequently, the
latency between the occurrence of the GPIB event and the invocation of the callback can be
large. On the other hand, you are not restricted in what you can do in the callback function.
Asynchronous Callbacks
You have the ability to install asynchronous callbacks on Windows NT and on Windows 95 with
the native 32-bit driver. Asynchronous callbacks are installed with the ibnotify function and
can be called at any time with respect to the rest of your program. Consequently, the latency
between the occurrence of the GPIB event and the invocation of the callback is smaller than with
synchronous callbacks, but you are restricted in what you can do in the callback function. See the
documentation of the ibnotify function later in this chapter for more details.
Driver Version Requirements
If you are using Windows NT, you must have version 1.2 or later of the GPIB driver to use the
ibInstallCallback and ibnotify functions.
If you are using the native 32-bit GPIB driver on Windows 95, you must have version 1.1 or later
to use the ibInstallCallback and ibnotify functions.
If you are using the Windows 3.1 compatibility driver on Windows 95, you can use the limited
version of ibInstallCallback, but you cannot use ibnotify.

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GPIB Function Reference
Most of the functions in the GPIB/GPIB-488.2 Library are described in the software reference
manual that you received with your GPIB board. This section contains descriptions only for the
Device Manager functions, the callback installation functions, and the functions for returning the
thread-specific status variables.
Note: ResetDevs is not available in LabWindows/CVI. This function was available in a
previous LabWindows version.

CloseDev
int result = CloseDev (int Device);
Purpose
Closes a device.
Parameter
Input

Device

integer

The device to be closed.

integer

Result of the close device
operation.

Return Value
result

Return Codes
-1
0

Error—cannot find device.
Success.

Using This Function
Takes a device offline. CloseDev performs an ibloc, then an ibonl with a value of zero.
Device is the device descriptor returned when the device was opened with OpenDev. If
CloseDev cannot find the device descriptor in its table, a -1 is returned. CloseDev should
be used only in conjunction with OpenDev. Never call CloseDev with a device descriptor
obtained by calling ibfind.

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CloseInstrDevs
int result = CloseInstrDevs (char *instrumentPrefix);
Purpose
Closes instrument devices.
Parameter
Input

instrumentPrefix

string

Must be null-terminated.

integer

Result of the close instrument
devices operation.

Return Value
result

Return Codes
0

Success.

Using This Function
Closes all devices associated with the instrument module whose prefix is specified.
instrumentPrefix is a string that specifies the prefix of the instrument module being closed.
CloseInstrDevs always returns zero. CloseInstrDevs should be used only in
conjunction with OpenDev.

ibInstallCallback
int status = ibInstallCallback (int boardOrDevice, int eventMask,
GPIBCallbackPtr callbackFunction,
void *callbackData)
Note: This function is available only on Microsoft Windows. On UNIX, use the ibsgnl
function. On Windows 3.1, the data type of the return value and the first two
parameters is short rather than int.
Purpose
This function allows you to install a synchronous callback function for a specified board or
device. If you want to install an asynchronous callback, use the ibnotify function instead.

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The callback function is called when any of the GPIB events specified in the Event Mask
parameter have occurred on the board or device, but only while you allow the system to process
events. The system can process events when you call ProcessSystemEvents or
GetUserEvent, or when you have called RunUserInterface and none of your callback
functions are currently active. The callbacks are termed "synchronous" because they can be
invoked only in the context of normal event processing.
Unlike asynchronous callbacks, there are no restrictions on what you can do in a synchronous
callback. On the other hand, the latency between the occurrence of a GPIB event and the
invocation of the callback function is greater and more unbounded with synchronous callbacks
than with asynchronous callbacks.
Only one callback function can apply for each board or device. Each call to this function for the
same board or device supersedes the previous call.
To disable callbacks for a board or device, pass 0 for the event Mask parameter.
To use this function with the NI-488.2M (native 32-bit) driver, you must have one of the
following versions.
•

For Windows 95: Version 1.1 or later.

•

For Windows NT: Version 1.2 or later.

If you use the NI-488.2 driver (the Windows 3.1 driver or the compatibility driver in Windows 95),
you must pass a board index for the first parameter, and you can use only SRQI or CMPL for the
event mask parameter.
Parameters
Input

boardOrDevice

integer
(short integer on
Windows 3.1)

A board index, or a board or device descriptor
returned by OpenDev, ibfind, or ibdev.
(On Windows 3.1, must be a board index).

eventMask

integer
(short integer on
Windows 3.1)

Specifies the events upon which the callback
function is called. Pass 0 to disable callbacks.
See discussion below.

callbackFunction

GPIBCallbackPtr The name of the user function that is called
when the specified events occur. See
discussion below.

callbackData

void pointer

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Return Value
status

integer
(short integer on
Windows 3.1)

The same value as the ibsta status variable.
Refer to your NI-488.2 or NI-488.2M user
manual for a description of the values of
ibsta status variable.

eventMask
The conditions upon which to invoke the callback function are specified as bits in the
eventMask parameter. The bits corresponds to the bits of the ibsta status word. This value
reflects a sum of one or more events. If any one of the conditions occur, the callback is called.
If, when you install the callback, one of the bits you have set in the mask is already TRUE, the
callback is scheduled immediately. For example, if you pass CMPL as the eventMask, and the
ibwait function would currently return a status word with CMPL set, the callback is scheduled
immediately.
If you are using a NI-488.2M (native 32-bit) driver then the following mask bits are valid:
•

At the board level, you can specify any of the status word bits that can be specified in the
waitMask parameter to the ibwait function for a board, other than ERR. This includes
SRQI, END, CMPL, TIMO, CIC, and others.

•

At the device level, you can specify any of the status word bits that can be specified in the
waitMask parameter to the ibwait function for a device, other than ERR. This includes
RQS, END, CMPL, and TIMO.

If you are using a NI-488.2 driver (Windows 3.1 or compatibility driver for Windows 95), then
the only following mask bits are valid:
SRQI or CMPL but not both.
SRQI, RQS, and Auto Serial Polling
If you want to install a callback for the SRQI (board-level) event, Auto Serial Polling must be
disabled. You can disable Auto Serial Polling with the following function call:
ibconfig (boardIndex, IbcAUTOPOLL, 0);

If you want to install a callback for the RQS (device-level) event, Auto Serial Polling must be
enabled for the board. You can enable Auto Serial Polling with the following function call:
ibconfig (boardIndex, IbcAUTOPOLL, 1);

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CallbackFunction
The callback function must have the following form.
void CallbackFunctionName (int boardOrDevice, int mask, void *callbackData);
The mask and callbackData parameters are the same values that were passed to
ibInstallCallback.
If invoked because of an SRQI or RQS condition, the callback function should call the ibrsp
function to read the status byte. For an SRQI (board-level) condition, calling the ibrsp
function is necessary to cause the requesting device to turn off the SRQ line.
char statusByte;
ibrsp (device, &statusByte);

If invoked because an asynchronous I/O operation (started by ibrda, ibwrta, or ibcmda)
completed, the callback function should contain the following call:
ibwait (boardOrDevice, TIMO | CMPL);

The ibcnt and ibcntl status variables are not updated until this call to ibwait is made.
See Also
ibnotify

ibNotify
int status = ibnotify (int boardOrDevice, int eventMask,
GpibNotifyCallback_t callbackFunction, void *callbackData);
Note: This function is available only on Windows 95 and NT. On UNIX, use the ibsgnl
function.
Purpose
This function allows you to install an asynchronous callback function for a specified board or
device. If you want to install a synchronous callback, use the ibInstallCallback function
instead.
The callback function is called when any of the GPIB events specified in the eventMask
parameter have occurred on the specified board or device. Asynchronous callbacks can be called
at any time while your program is running. You do not have to allow the system to process
events. Because of this, you are restricted in what you can do in the callback. See the
Restrictions on Operations in Asynchronous Callbacks discussion below.

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Only one callback function can apply for each board or device. Each call to this function for the
same board or device supersedes the previous call.
To disable callbacks for a board or device, pass 0 for the eventMask parameter.
Parameters
Input

boardOrDevice

integer

A board index, or a board or device
descriptor returned by OpenDev,
ibfind, or ibdev.

eventMask

integer

Specifies the events upon which the
callback function is called. Pass 0 to
disable callbacks. See discussion below.

callbackFunction

GpibNotifyCallback_t

The name of the user function that is
called when the specified events occur.
See discussion below.

callbackData

void pointer

A pointer to a user-defined four-byte
value that is passed to the callback
function.

integer

The same value as the ibsta status
variable. Refer to your NI-488.2M user
manual for a description of the values of
ibsta status variable.

Return Value
status

eventMask
The conditions upon which to invoke the callback function are specified as bits in the
eventMask parameter. The bits corresponds to the bits of the ibsta status word. This value
reflects a sum of one or more events. If any one of the conditions occur, the callback is called.
If, when you install the callback, one of the bits you have set in the mask is already TRUE, the
callback is called immediately. For example, if you pass CMPL as the eventMask, and the
ibwait function would currently return a status word with CMPL set, the callback is called
immediately.
At the board level, you can specify any of the status word bits that can be specified in the
waitMask parameter to the ibwait function for a board, other than ERR. This includes SRQI,
END, CMPL, TIMO, CIC, and others.
At the device level, you can specify any of the status word bits that can be specified in the
waitMask parameter to the ibwait function for a device, other than ERR. This includes RQS,
END, CMPL, and TIMO.
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SRQI, RQS, and Auto Serial Polling
If you want to install a callback for the SRQI (board-level) event, Auto Serial Polling must be
disabled. You can disable Auto Serial Polling with the following function call:
ibconfig (boardIndex, IbcAUTOPOLL, 0);

If you want to install a callback for the RQS (device-level) event, Auto Serial Polling must be
enabled for the board. You can enable Auto Serial Polling with the following function call:
ibconfig (boardIndex, IbcAUTOPOLL, 1);

CallbackFunction
The callback function must have the following form.
void __stdcall CallbackFunctionName (int boardOrDevice, int sta, int err,
long cntl, void *callbackData);
The callbackData parameter is the same callbackData value passed to
ibInstallCallback. The sta, err, and cntl parameters contain the information that you
normally obtain using the ibsta, iberr, and ibcntl global variables or the
ThreadIbsta, ThreadIberr, and ThreadIbcntl functions. The global variables and
thread status functions return undefined values within the callback function. So you must use the
sta, err and cntl parameters instead.
The value that you return from the callback function is very important. It is the event mask that is
used to rearm the callback. If you return 0, the callback is disarmed (that is, it is not called again
until you make another call to ibnotify). If you return an event mask different than the one
you originally passed to ibnotify, the new event mask is used. Normally, you want to return
the same event mask that you originally passed to ibnotify.
If you return an invalid event mask or if there is an operating system error in rearming the
callback, the callback is called with the sta set to ERR , err set to EDVR, and cntl set to
IBNOTIFY_REARM_FAILED.
Warning:

Because the callback can be called as the result of a rearming error, you should
always check the value of the sta parameter to make sure that one of the
requested events has in fact occurred.

If invoked because of an SRQI or RQS condition, the callback function should call the ibrsp
function to read the status byte. For an SRQI (board-level) condition, calling the ibrsp
function is necessary to cause to requesting device to turn off the SRQ line.
char statusByte;
ibrsp (device, &statusByte);

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If invoked because an asynchronous I/O operation (started by ibrda, ibwrta, or ibcmda)
completed, the callback function should contain the following call:
ibwait (boardOrDevice, TIMO | CMPL);

The ibcnt and ibcntl status variables are not updated until this call to ibwait is made.
Restrictions on Operations in Asynchronous Callbacks
Callbacks installed with ibnotify can be called at any time while your program is running.
You do not have to allow the system to process events. Because of this, you are restricted in what
you can do in the callback. You can do the following:
•

Call the User Interface Library PostDeferredCall function, which schedules a different
callback function to be called synchronously.

•

Call any GPIB function, except ibnotify or ibInstallCallback.

•

Manipulate global variables, but only if you know that the callback has not been called at a
point when the main part of your program is modifying or interrogating the same global
variables.

•

Call ANSI C functions such as strcpy and sprintf, which affect only the arguments
passed in (that is, have no side effects). You cannot call printf or file I/O functions.

•

Call malloc, calloc, realloc, or free.

If you need to perform operations that fall outside these restrictions, do the following.
1.

In your asynchronous callback, perform the time-critical operations in the asynchronous
callback, and call PostDeferredCall to schedule a synchronous callback.

2.

In the synchronous callback, perform the other operations.

See Also
ibInstallCallback

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OpenDev
int bd = OpenDev (char *deviceName, char *instrumentPrefix);
Purpose
Opens a GPIB device.
Parameters
Input

deviceName

string

Must be null-terminated.

instrumentPrefix

string

Must be null-terminated.

integer

Result of the open device
operation.

Return Value
bd

Return Codes
-1

Device table is full, or no more devices available.

Parameter Discussion
deviceName is a string specifying a device name that appears in the IBCONF device table. If
deviceName is not "", OpenDev acts identically to ibfind. If deviceName is "", OpenDev
acts identically to ibdev. OpenDev uses the first available unopened device.
instrumentPrefix is a string that specifies the instrument prefix associated with the instrument
module. The instrument prefix must be identical to the prefix entered when creating the function
tree for the instrument module. If the instrument module has no prefix or if OpenDev is not
being used in an instrument module, pass the string "" for instrumentPrefix.
Using This Function
This function attempts to find an unused device in the GPIB handler's device table and open it. If
successful, OpenDev returns a device descriptor. Otherwise, it returns a negative number.

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ThreadIbcnt
int threadSpecificCount = ThreadIbcnt (void);
Note: This function is available only under Windows 95 and NT.
This function returns the value of the thread-specific ibcnt variable for the current thread.
The global variables ibsta, iberr, ibcnt, and ibcntl are maintained on a process-specific
(rather than thread-specific) basis. If you are calling GPIB functions in more than one thread, the
values in these global variables may not always be reliable.
Status variables analogous to ibsta, iberr, ibcnt, and ibcntl are maintained for each
thread. This function returns the value of the thread-specific ibcnt variable.
If you are not using multiple threads, the value returned by this function is identical to the value
of the ibcnt global variable.
Parameters
none
Return Value
threadSpecificCount

integer The number of bytes actually transferred by the most recent
GPIB read, write, or command operation for the current thread
of execution. If an error occurred loading the GPIB DLL, this
is the error code returned by the MS Windows
LoadLibrary function.

See Also
ThreadIbsta, ThreadIberr, ThreadIbcntl.

ThreadIbcntl
long threadSpecificCount = ThreadIbcntl (void);
Note: This function is available only under Windows 95 and NT.
This function returns the value of the thread-specific ibcntl variable for the current thread.
The global variables ibsta, iberr, ibcnt, and ibcntl are maintained on a process-specific
(rather than thread-specific) basis. If you are calling GPIB functions in more than one thread, the
values in these global variables may not always be reliable.
Status variables analogous to ibsta, iberr, ibcnt, and ibcntl are maintained for each
thread. This function returns the value of the thread-specific ibcntl variable.

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If you are not using multiple threads, the value returned by this function is identical to the value
of the ibcntl global variable.
Parameters
none
Return Value
threadSpecificCount long
integer

The number of bytes actually transferred by the most
recent GPIB read, write, or command operation for the
current thread of execution. If an error occurred loading
the GPIB DLL, this is the error code returned by the MS
Windows LoadLibrary function.

See Also
ThreadIbsta, ThreadIberr, ThreadIbcnt.

ThreadIberr
int threadSpecificError = ThreadIberr (void);
Note: This function is available only under Windows 95 and NT.
This function returns the value of the thread-specific iberr variable for the current thread.
The global variables ibsta, iberr, ibcnt, and ibcntl are maintained on a process-specific
(rather than thread-specific) basis. If you are calling GPIB functions in more than one thread, the
values in these global variables may not always be reliable.
Status variables analogous to ibsta, iberr, ibcnt, and ibcntl are maintained for each
thread. This function returns the value of the thread-specific iberr variable.
If you are not using multiple threads, the value returned by this function is identical to the value
of the iberr global variable.
Parameters
none
Return Value
threadSpecificError

integer

© National Instruments Corporation

The most recent GPIB error code for the current thread of
execution. The value is meaningful only when
ThreadIbsta returns a value with the ERR bit set.

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Return Codes
Defined
Constant

Value

Description

EDVR

0

Operating system error. The system-specific error code is returned by
ThreadIbcntl.

ECIC

1

Function requires GPIB-PC to be CIC.

ENOL

2

No listener on write function.

EADR

3

GPIB-PC addressed incorrectly.

EARG

4

Invalid function call argument.

ESAC

5

GPIB-PC not System Controller as required.

EABO

6

I/O operation aborted.

ENEB

7

Non-existent GPIB-PC board.

EDMA

8

Virtual DMA device error.

EOIP

10

I/O started before previous operation completed.

ECAP

11

Unsupported feature.

EFSO

12

File system error.

EBUS

14

Command error during device call.

ESTB

15

Serial Poll status byte lost.

ESRQ

16

SRQ stuck in on position.

ETAB

20

Device list error during a FindLstn or FindRQS call.

ELCK

21

Address or board is locked.

ELNK

200

The GPIB library was not linked. Dummy functions were linked instead.

EDLL

201

Error loading GPIB32.DLL. The MS Windows error code is returned by
ThreadIbcntl.

EFNF

203

Unable to find the function in GPIB32.DLL. The MS Windows error
code is returned by ThreadIbcntl.

EGLB

205

Unable to find globals in GPIB32.DLL. The MS Windows error code is
returned by ThreadIbcntl.

ENNI

206

Not a National Instruments GPIB32.DLL.

EMTX

207

Unable to acquire Mutex for loading DLL. The MS Windows error code
is returned by ThreadIbcntl.

EMSG

210

Unable to register callback function with MS Windows.

ECTB

211

The callback table is full.

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See Also
ThreadIbsta, ThreadIbcnt, ThreadIbcntl.

ThreadIbsta
int threadSpecificStatus = ThreadIbsta (void);
Note: This function is available only under Windows 95 and NT.
This function returns the value of the thread-specific ibsta variable for the current thread.
The global variables ibsta, iberr, ibcnt, and ibcntl are maintained on a process-specific
(rather than thread-specific) basis. If you are calling GPIB functions in more than one thread, the
values in these global variables may not always be reliable.
Status variables analogous to ibsta, iberr, ibcnt, and ibcntl are maintained for each
thread. This function returns the value of the thread-specific ibsta variable.
If you are not using multiple threads, the value returned by this function is identical to the value
of the ibsta global variable.
Parameters
none
Return Value
threadSpecificStatus

integer

© National Instruments Corporation

The status value for the current thread of execution. The
status value describes the state of the GPIB and the result
of the most recent GPIB function call in the thread. Any
value with the ERR bit set indicates an error. Call
ThreadIberr for a specific error code.

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Return Codes
The return value is a sum of the following bits.
Defined
Constant

Hex Value

Condition

ERR

8000

GPIB error.

END

2000

END or EOS detected.

SRQI

1000

SRQ is on.

RQS

800

Device requesting service.

CMPL

100

I/O completed.

LOK

80

GPIB-PC in Lockout State.

REM

40

GPIB-PC in Remote State.

CIC

20

GPIB-PC is Controller-In-Charge.

ATN

10

Attention is asserted.

TACS

8

GPIB-PC is Talker.

LACS

4

GPIB-PC is Listener.

DTAS

2

GPIB-PC in Device Trigger State.

DCAS

1

GPIB-PC in Device Clear State.

See Also
ThreadIberr, ThreadIbcnt, ThreadIbcntl

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RS-232 Library
This chapter describes the functions in the LabWindows/CVI RS-232 Library. The RS-232
Library Function Overview section contains general information about the RS-232 Library
functions and panels. The RS-232 Library Function Reference section contains an alphabetical
list of function descriptions.
In order to use the RS-232 Library on UNIX, your UNIX kernel must support asynchronous I/O
functions (for example, aioread and aiowrite). You can enable this by building your
UNIX kernel as Generic instead of Generic Small.

RS-232 Library Function Overview
This section contains general information about the RS-232 Library functions and panels. The
RS-232 Library can also be used with a National Instruments RS-485 serial board.

The RS-232 Library Function Panels
The RS-232 Library function panels are grouped in a tree structure according to the types of
operations performed. The RS-232 Library function tree appears in Table 5-1.
The first- and second-level bold headings in the tree are the names of function classes and
subclasses. Function classes and subclasses are groups of related function panels. The thirdlevel headings in plain text are the names of individual function panels. Each RS-232 function
panel generates one or more RS-232 function calls. The names of functions are in bold italics to
the right of the function panel name.
Table 5-1. The RS-232 Library Function Tree
RS-232
Open/Close
Open COM and Configure
Close COM
Open COM—Current State
Input/Output
Read Buffer
Read Terminated Buffer
Read Byte

OpenComConfig
CloseCom
OpenCom
ComRd
ComRdTerm
ComRdByte
(continues)

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Table 5-1. The RS-232 Library Function Tree (Continued)
Read To File
Write Buffer
Write Byte
Write From File
XModem
XModem Send File
XModem Receive File
XModem Configure
Control
Set Time-out Limit
Set XON/XOFF Mode
Set CTS Mode
Flush Input Queue
Flush Output Queue
Send Break Signal
Set Escape Code
Status
Get COM Status
Get Input Queue Length
Get Output Queue Length
Return RS232 Error
Get Error String
Callbacks
Install COM Callback

ComToFile
ComWrt
ComWrtByte
ComFromFile
XModemSend
XModemReceive
XModemConfig
SetComTime
SetXMode
SetCTSMode
FlushInQ
FlushOutQ
ComBreak
ComSetEscape
GetComStat
GetInQLen
GetOutQLen
ReturnRS232Err
GetRS232ErrorString
InstallComCallback

The classes and subclasses in the tree are described below.
•

The Open/Close function panels open, close and configure a com port.

•

The Input/Output function panels read from and write to a com port.

•

The XModem function panels transfer files using the XModem protocol.

•

The Control function panels set the time-out limit, set communication modes, flush the I/O
queues, and send the break signal.

•

The Status function panels return the com port status and the length of the I/O queues.

•

The Callbacks function panel installs callback functions for COM events.

The online help with each panel contains specific information about operating each function
panel.

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Using RS-485
You can use all of the functions in the RS-232 Library with the National Instruments RS-485
AT-Serial board. The ComSetEscape function allows you to control the transceiver mode of
the board.

Reporting RS-232 Errors
The functions in the RS-232 Library return negative values when an error occurs. In addition, the
global variable rs232err is updated after each function call to the RS-232 Library. If the
function executes properly, it sets rs232err to zero. Otherwise, it sets rs232err to the same
error code that it returns. A list of the possible error conditions that can occur while using the
RS-232 Library functions are at the end of this chapter.

XModem File Transfer Functions
With the XModem functions, you can transfer files using a data transfer protocol. The protocol
uses a generally accepted technique for serial file transfers with error-checking. Files transfer
packets that contain data from the files plus error-checking and synchronization information.
You do not need to understand the protocol to use the functions. To transfer a file, open the com
port, use the XModemSend function on the sender side of the transfer and the
XModemReceive function on the receiver side of the transfer, and then close the com port.
The XModem functions handle all aspects of the transfer protocol.
You can treat the XModem functions as higher-level functions that perform a more precisely
defined task than the functions ComToFile and ComFromFile. Use ComToFile and
ComFromFile if you need finer control over the file operations. Remember that the Xmodem
functions calculate the check sum and retransmit when an error is detected, whereas
ComToFile and ComFromFile do not do so.

Troubleshooting
Establishing communication between two RS-232 devices can be difficult because of the many
different possible configurations. When using this library, you must know the device
requirements, such as baud rate, parity, number of data bits, and number of stop bits. Basically,
these configurations must match between the two parties of communication.
If you encounter difficulty in establishing initial communication with the device, refer to an
elementary RS-232 communications handbook for information about cable requirements and
general RS-232 communication. Refer also to the section RS-232 Cable Information later in this
chapter.

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All functions, except the Open and Close functions, require the com port to be opened with
OpenCom or OpenComConfig.
If the program writes data to the output queue and then immediately closes the com port, the data
in the queue may be lost if it has not had time to be sent over the port. To guarantee that all bytes
were written before closing the port, monitor the length of the output queue with the
GetOutQLen function. When the output queue length becomes zero, it is safe to close the port.
If the XModemReceive function fails to complete properly, verify that the input queue length
is greater than or equal to the packet size. Refer to the functions OpenComConfig and
XModemConfig.
If the receiver appears to lose data transmitted by the sender, the input queue of the receiver may
be overflowing. This means that the input queue of the receiver is not emptied as quickly as data
is coming in. You can solve this problem using handshaking, provided both devices offer the
same handshaking support. Refer to the Handshaking section of this chapter for further
information.
If an XModem file transfer with a large packet size and a low baud rate fails, you might need to
increase the wait period. Ten seconds is sufficient for most transfers.

RS-232 Cable Information
An RS-232 cable consists of wires, or lines, that are joined with a connector at each end. The
connectors plug into the serial ports of each device to form a communications link over which
data and control signals flow. Each serial port consists of pins that are numbered and have
meaning. The PC pins are numbered and described as shown in Table 5-2.
Table 5-2. PC Cable Configuration
Pin

Meaning

2

TxD—Transmit Data *

3

RxD—Receive Data

4

RTS—Request to Send *

5

CTS—Clear to Send

6

DSR—Data Set Ready

20

DTR—Data Terminal Ready *

7

Common

The items with an asterisk (*) indicate the lines that the PC drives, and all other items indicate
the lines the PC monitors.

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All serial devices are either of the type Data Communication Equipment (DCE) or Data
Transmission Equipment (DTE). The PC is of type DTE. The difference between the two
devices is in the meaning assigned to the pins. A DCE device reverses the meaning of pins 2 and
3, 4 and 5, and 6 and 20. In the simplest scenario, a DTE device is attached to a DCE device,
such as a modem. Therefore, the cable required for a PC (or DTE) to talk to a device that is a
DCE is shown in Table 5-3.
Table 5-3. DTE to DCE Cable Configuration
(PC)
TxD*
RxD
RTS*
CTS
DSR
DTR*
common

Connect pins as indicated:
2_______________ 2

(Device)

3_______________ 3
4_______________ 4

TxD*

5_______________ 5
6_______________ 6

RTS*

20 ______________20
7_______________ 7

DSR*

RxD
CTS
DTR
common

You need a different cable for the PC to talk to a DTE device, because both devices transmit data
over pin 2. The cable to connect a PC to a DTE is called a null modem cable. A null modem
cable must be built as shown in Table 5-4.
Table 5-4. PC to DTE Cable Configuration
(PC)
TxD*
RxD
RTS*
CTS
DSR
DTR*
common

Connect pins as indicated:
2_______________ 3

(Device)

3_______________ 2
4_______________ 5

TxD*

5_______________ 4
6_______________20

RTS*

20 ______________ 6
7_______________ 7

RxD
CTS
DTR
DSR*
common

For further information on the meaning of DTE and DCE, refer to a reference book on RS-232
communication.
In the simplest case, a serial cable needs lines 2, 3, and 7 for basic communication to take place.
Hardware handshaking and modem control can require other lines, depending on your

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application. Refer to the Hardware Handshaking section later in this chapter for more
information about using the lines 4, 5, 6, and 20.
Another area that requires special attention is the gender of the connectors of your serial cable.
The serial cable plugs into sockets in the PC and the serial device just as a lamp cord plugs into a
wall socket. Both the connector and the socket can be male, with pins (like a lamp plug), or
female, with holes (like an outlet). If your serial cable connector and PC socket are the same
gender, you cannot plug the cable into the socket. You can change this by attaching a small
device called a gender changer to your cable. One type of gender changer converts a female
connector to a male connector and the other type converts a male connector to a female
connector.
The size of the connector on your serial cable can also differ from the size of the socket. Most
serial ports require a 25-pin connector. However, some serial ports require a 9-pin connector.
To resolve this incompatibility, you must either change the connector on your serial cable or
attach a small device that converts from a 25-pin connector to a 9-pin connector.

Handshaking
A common error condition in RS-232 communications is that the receiver appears to lose data
transmitted by the sender. This condition typically results from the input queue of the receiver
not being emptied quickly enough.
Handshaking prevents overflow of the input queue that occurs when the receiver is unable to
empty its input queue as quickly as the sender is able to fill it. The RS-232 Library has two types
of handshaking: software handshaking and hardware handshaking. You should enable one or the
other if you want to ensure that your application program synchronizes its data transfers with
other serial devices that perform handshaking.
Software Handshaking
The SetXMode function enables software handshaking. You can use software handshaking
when you are transferring ASCII data or text and your serial device uses software handshaking.
The RS-232 Library performs software handshaking by sending and monitoring incoming data
for special data bytes (XON and XOFF, or decimal 17 and 19). These bytes indicate whether the
receiver is ready to receive data.
You must not enable software handshaking when transmitting binary data because the special
XON/XOFF characters can occur as part of the data stream and are mistaken as control codes.
However, you can enable hardware handshaking regardless of the type of data transferred.
No special cable configuration is required to perform software handshaking.

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Hardware Handshaking
The SetCTSMode function enables hardware handshaking. For hardware handshaking to work,
two conditions must exist. First, the serial devices must follow the same or similar hardware
handshake protocols (they must use the same lines for the handshake and assign the same
meanings to those lines). Second, the serial cable connecting the two devices must include the
lines required to support the protocol. Because no single well-defined hardware handshake
protocol exists, resolve any differences between the LabWindows/CVI hardware handshake
protocol and the one your device uses.
Most serial devices primarily rely on the CTS and RTS lines to perform hardware handshaking,
and the DTR line is used to signal its online presence to the other device. Some serial devices
also may use the DTR line for hardware handshaking similarly to the CTS line. The
SetCTSMode function has two different modes to handle either case.
This SetCTSMode function employs the following line behaviors for each mode.
Note: Under UNIX, changes to the DTR line have no effect on the communication port.
LWRS_HWHANDSHAKE_OFF
•

The RTS and DTR lines are raised when opening the port and lowered when closing the port.
Data is sent out the port regardless of the status of CTS.
Note: Under Windows, the SetComEscape function can be used to change the value of
the RTS and DTR lines.

LWRS_HWHANDSHAKE_CTS_RTS
•

•

When the PC is the receiver:
–

If the port is opened, the library raises RTS and DTR.

–

If the input queue of the port is nearly full, the library lowers RTS.

–

If the input queue of the port is nearly empty, the library raises RTS.

–

If the port is closed, the library lowers RTS and DTR.

When the PC is the sender:
–

The RS-232 library must detect that its CTS line is high before sending data out the port.

LWRS_HWHANDSHAKE_CTS_RTS_DTR
•

When the PC is the receiver:
–

If the port is opened, the library raises RTS and DTR.

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•

Chapter 5

–

If the input queue of the port is nearly full, the library lowers RTS and DTR.

–

If the input queue of the port is nearly empty, the library raises RTS and DTR.

–

If the port is closed, the library lowers RTS and DTR.

When the PC is the sender:
–

The RS-232 library must detect that its CTS line is high before sending data out the port.

Note: The only difference between LWRS_HWHANDSHAKE_CTS_RTS and
LWRS_HWHANDSHAKE_CTS_RTS_DTR is the behavior of the DTR line.
If the handshaking mechanism used by your device uses the CTS and RTS lines, use a serial
cable as shown in Table 5-3 if your device is a DCE, or Table 5-4 if your device is a DTE.
Optionally, your cable can omit the connection between pins 6 and 20 if your device does not
monitor DSR when sending data. Notice that the RTS pin of the receiver translates to the CTS
pin of the sender, and the DSR pin of the receiver translates to the DTR pin of the sender.
If you want to use hardware handshaking but your device uses a different hardware handshake
protocol than the ones described here, you can build a cable that overcomes the differences. You
can construct a cable to serve your special needs be referencing the pin description in Table 5-2.

RS-232 Library Function Reference
This section describes each function in the LabWindows/CVI RS-232 Library. The
LabWindows/CVI RS-232 Library functions are arranged alphabetically.

CloseCom
int result = CloseCom (int COMPort);
Purpose
Closes a COM port.
Parameter
Input

COMPort

integer

Range 1 through 32.

integer

Refer to error codes in
Table 5-6.

Return Value
result

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Parameter Discussion
The function does nothing if the port numbers are invalid (port is not open or parameter value is
not in the range 1 through 32).

ComBreak
int result = ComBreak (int COMPort, int breakTimeMsec);
Purpose
Generates a break signal.
Parameters
Input

COMPort

integer

Range 1 through 32.

breakTimeMsec

integer

Range 1 through 255, or 0 to
select 250.

integer

Refer to error codes in
Table 5-6.

Return Value
result

Using This Function
The function generates a break signal for the number of milliseconds indicated or for 250 ms if
the breakTimeMsec parameter is zero. For most applications, 250 ms is adequate.
Errors may occur if the port is not open or parameter values are invalid.

ComFromFile
int nbytes = ComFromFile (int COMPort, int fileHandle, int count,
int terminationByte);
Purpose
Reads from the specified file and writes to output queue of the specified COM port.

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Parameters
Input

COMPort

integer

Range 1 through 32.

fileHandle

integer

File handle returned by
OpenFile.

count

integer

If 0, this value is ignored.

terminationByte

integer

If -1, this value is ignored.

integer

Number of bytes written to the
output queue.

Return Value
nbytes
<0

Error. Refer to error codes in
Table 5-6.

Parameter Discussion
Reads count bytes from the file unless it encounters terminationByte, reaches EOF, or
encounters an error. The function returns the number of bytes successfully written to the output
queue. The function returns immediately after placing all bytes in the output queue, not when
bytes have all been sent out the com port.
If count is zero, the function terminates on terminationByte, EOF, or error.
If terminationByte is -1, it is ignored, and the function terminates on count bytes written, EOF,
or error. If terminationByte is not -1, reading from the file stops when terminationByte is
encountered. It does not write terminationByte to the output queue. If terminationByte is CR
or LF, then the function treats CR-LF and LF-CR combinations just as ComRdTerm does.
If both count and terminationByte are disabled, the function terminates on EOF or error.
Using This Function
To guarantee that all bytes were removed from the output queue before closing the port, call
GetOutQLen to determine the number of bytes remaining in the output queue. If you close the
port before every byte has been sent, you lose the bytes remaining in the queue.
The function returns a negative error code if the output queue remains full for the duration of the
time-out period, the file handle is bad, a read error occurs, the port is not open, or the COMPort
is invalid.

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ComRd
int nbytes = ComRd (int COMPort, char buffer[], int count);
Purpose
Reads count bytes from input queue of the specified port and stores them in buffer. Returns
either on time-out or when count bytes have been read. Returns an integer value indicating the
number of bytes read from queue.
Parameters
Input

Output

COMPort

integer

Range 1 through 16.

count

integer

0 value takes no bytes from
queue.

buffer

string

The buffer in which to store the
data.

integer

Number of bytes read from the
input queue.

Return Value
nbytes

Using This Function
This function times out if the input queue remains empty in the specified time-out period. This
may occur when no data has been received within the time-out period.
The function returns an error code if the port is not open or parameter values are invalid.
Example
/* Read 100 bytes from input queue of COM1 into buf. */
int n;
char buf[100];
:
n = ComRd (1, buf, 100);
if (n != 100)
/* Time-out or error occurred before read completed. */ ;

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ComRdByte
int byte = ComRdByte (int COMPort);
Purpose
Reads a byte from the input queue of the specified port. Returns an integer whose low-order byte
contains the byte read. Returns either on time-out, when the byte is read, or when an error occurs.
If an error or a time-out occurs, ComRdByte returns a negative error code. See Table 5-6. This is
the only case in which the high-order byte of the return value is non-zero.
Parameter
Input

COMPort

integer

Range 1 through 32.

integer

Low order byte contains the
byte read.

Return Value
byte
<0

Error.

Using This Function
This function times out if the input queue remains empty in the specified time-out period. This
may occur when no data has been received within the time-out period.
The function returns an error code if the port is not open, COMPort is invalid, or a time-out
occurs.

ComRdTerm
int nbytes = ComRdTerm (int COMPort, char buffer[], int count,
int terminationByte);
Purpose
Reads from input queue until terminationByte occurs in buffer, count is met, or a time-out
occurs. Returns integer value indicating number of bytes read from queue.

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Parameters
Input

Output

COMPort

integer

Range 1 through 32.

count

integer

If 0, no bytes are removed from
queue.

terminationByte

integer

Low byte contains the numeric
equivalent of the terminating
character.

buffer

string

The buffer in which to store the
data.

integer

Number of bytes read from the
input queue.

Return Value
nbytes

Using This Function
This function times out if the input queue remains empty within the specified time-out period.
This may occur when no data has been received during the time-out period. If the read
terminates on the termination byte, the byte is neither written to the buffer nor included in the
count.
If the termination character is either a carriage return (CR or decimal 13) or a linefeed (LF or
decimal 10), the function handles it as follows:
•

If terminationByte = CR, and if the character immediately following CR is LF, discard the
LF in addition to the CR.

•

If terminationByte = LF, and if the character immediately following LF is CR, discard the
CR in addition to the LF.

Only the bytes placed in buffer are included in the return count. If CR or LF is discarded
because it follows an LF or CR, it is not counted toward satisfying the count.
The function returns an error if the port is not open or parameter values are invalid.

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ComSetEscape
int result = ComSetEscape (int COMPort, int escapeCode);
Purpose
Directs the specified com port to carry out an extended function such as clearing or setting the
RTS signal line or setting the transceiver mode for RS-485. The extended functions are defined
by the serial device driver.
Not all device drives support all escape codes. Unknown System Error (-1) is returned when the
device driver does not support a particular escape code.
Note: This function is supported in the MS Windows version of LabWindows/CVI only.
Parameters
Input

COMPort

integer Range 1 through 32.

escapeCode

integer Specifies the escape code of the extended
function.

Return Value
result

integer

Error Code. Refer to Table 5-6.

Parameter Discussion
The following values can be used for escape code.
CLRDTR—Clears the DTR (data-terminal-ready) signal.
CLRRTS—Clears the RTS (request-to-send) signal.
GETMAXCOM—Returns the maximum com port identifier supported by the system. This value
ranges from 0x00 to 0x7F, such that 0x00 corresponds to COM1, 0x01 to COM2, 0x02 to
COM3, and so on.
SETDTR—Sends the DTR (data-terminal-ready) signal.
SETRTS—Sends the RTS (request-to-send) signal.
SETXOFF—Causes the port to act as if an XOFF character has been received.
SETXON—Causes the port to act as if an XON character has been received.

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The following values may be used only with the RS-485 serial driver developed by National
Instruments:
WIRE_4—Sets the transceiver to Four Wire Mode.
WIRE_2_ECHO—Sets the transceiver to Two Wire DTR controlled with echo mode.
WIRE_2_CTRL—Sets the transceiver to Two Wire DTR controlled without echo.
WIRE_2_AUTO—Sets the transceiver to Two Wire auto TXRDY controlled mode.

ComToFile
int nbytes = ComToFile (int COMPort, int fileHandle, int count,
int terminationByte);
Purpose
Reads from input queue of specified com port and write data to file specified by fileHandle.
Returns number of bytes successfully written to file. Bytes are read from input queue until count
is satisfied, terminationByte is encountered, or an error occurs, whichever occurs first.
Parameters
Input

COMPort

integer

Range 1 through 32.

fileHandle

integer

File handle returned by
OpenFile.

count

integer

If 0, this value is ignored.

terminationByte

integer

If -1, this value is ignored.

integer

Number of bytes written to the
file.

Return Value
nbytes

Parameter Discussion
If count is zero, the function ignores it and terminates on terminationByte or error.
If terminationByte is -1, the function ignores it and terminates on count bytes read or an error.
If terminationByte is valid, the function stops when it encounters terminationByte.
terminationByte is removed from the input queue and is not written to the file. If
terminationByte is CR or LF, then CR-LF and LF-CR combinations are treated just as they are

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for ComRdTerm. If both count and terminationByte are disabled, the function terminates on
error (which can include a time-out).
Using This Function
The function returns an error if the output queue remains full for the duration of the time-out
period, the file handle is bad, a read error occurs, the port is not open, or the COMPort is
invalid.

ComWrt
int nbytes = ComWrt (int COMPort, char buffer[], int count);
Purpose
Writes count bytes to the output queue of the specified port. Returns an integer value indicating
the number of bytes placed in the queue. Returns immediately without waiting for the bytes to
be sent out of the serial port.
Parameters
Input

COMPort

integer

Range 1 through 32.

buffer

string

Buffer containing data to be written, or actual
string.

count

integer

0 value places no bytes in queue.

integer

Number of bytes placed in the output queue.

Return Value
nbytes
<0

Error code; See Table 5-6. Byte not placed in
the output queue.

Using This Function
This function times out if the output queue has not been updated in the specified time-out period.
This can occur if the output queue is full and no further data can be sent because XON/XOFF is
enabled and the device has sent an XOFF character without sending the follow-on XON
character. It can also occur if Hardware Handshaking is enabled and the Clear To Send (CTS)
line is not asserted.
Bytes are sent from the output queue to the serial device under interrupt control without program
intervention. If you close the port before all bytes have been sent, you lose the bytes remaining in
the queue. To guarantee that all bytes have been removed from the output queue before closing

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the port, call GetOutQLen. GetOutQLen returns the number of bytes remaining in the output
queue.
The function returns an error if the port is not open or parameter values are invalid.
Example
/*
/*
if
/*

Place the string "Hello, world!" in the output queue of */
COM2 and check if operation was successful. */
(ComWrt (2, "Hello, World!", 13) != 13)
Operation was unsuccessful */;

or
char buf[100];
Fmt(buf,"%s","Hello, World!");
if (ComWrt (2, buf, 13) != 13)
/* Operation was unsuccessful */;

ComWrtByte
int status = ComWrtByte (int COMPort, int byte);
Purpose
Writes a byte to the output queue of the specified port. The byte written is the low-order byte of
the integer. Returns a 1 to indicate the operation is successful, or a negative error code to indicate
the operation has failed. Returns immediately without waiting for the byte to be transmitted out
through the serial port.
Parameters
Input

COMPort

integer

Range 1 through 32.

byte

integer

Only the low-order byte is
significant.

integer

Result of the write operation.

Return Value
status
<0

Error code; See Table 5-6.

1

One byte placed in the output
queue.

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Parameter Discussion
This function times out if the output queue has not been updated in the specified time-out period.
This can occur if the output queue is full and no further data can be sent because XON/XOFF is
enabled and the device has sent an XOFF character without sending the follow-on XON
character. It can also occur if Hardware Handshaking is enabled and the Clear To Send (CTS)
line is not asserted.
Bytes are sent from the output queue to the serial device under interrupt control without program
intervention. If you close the port before all bytes have been sent, you lose the bytes remaining in
the queue. To guarantee that all bytes have been removed from the output queue before closing
the port, call GetOutQLen. GetOutQLen returns the number of bytes remaining in the output
queue.
The function returns an error if the port is not open or parameter values are invalid.

FlushInQ
int status = FlushInQ (int COMPort);
Purpose
Removes all characters from the input queue of the specified port.
Parameter
Input

COMPort

integer

Range 1 through 32.

integer

Refer to Error Codes in
Table 5-6.

Return Value
status

Using This Function
You can use this function to flush a flawed transmission in preparation for re-transmission. It
alleviates the need to read bytes into a buffer to empty the queue. If the queue is already empty,
this function does nothing.
The function returns a negative error code if the port is not open or if COMPort is invalid.

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FlushOutQ
int status = FlushOutQ (int COMPort);
Purpose
Removes all characters from the output queue of the specified port.
Parameter
Input

COMPort

integer

Range 1 through 32.

integer

Refer to Error Codes in
Table 5-6.

Return Value
status

Using This Function
The function returns an error if the port is not open or if COMPort is invalid.

GetComStat
int status = GetComStat (int COMPort);
Purpose
Returns information about the status of the specified COM port. COM port conditions are
accumulated until you call GetComStat.
Parameter
Input

COMPort

integer

Range 1 through 16.

integer

Bits indicate COM port status.

Return Value
status
<0

Error. Refer to Table 5-5.

Using This Function
Table 5-5 lists definitions of specific bits in the return value. Several bits can be set to indicate
the presence of more than one condition.

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Table 5-5. Bit Definitions for the GetComStat Function
Hex
Value

Mnemonic

Description

0001

INPUT LOST

Input queue filled and input characters lost (characters
were not removed fast enough).

0002

ASYNCH ERROR Problem determining number of characters in input queue.
This is an internal error and normally should not occur.

0010

PARITY

Parity error detected.

0020

OVERRUN

Overrun error detected; a character was received before
the receiver data register was emptied.

0040

FRAMING

Framing error detected; stop bits were not received when
expected.

0080

BREAK

Break signal detected.

1000

REMOTE XOFF

XOFF character received. If XON/XOFF was enabled (see
the SetXMode function description), no characters are
removed from the output queue and sent to the other device
until that device sends an XON character.

4000

LOCAL XOFF

XOFF character sent to the other device. If XON/XOFF
was enabled (see the SetXMode function description),
XOFF is transmitted when the input queue is 50%, 75%
and 90% full. If the other device is sensitive to
XON/XOFF protocol, it transmits no further characters
until it receives an XON character. You use this process to
avoid the INPUT LOST error.

Notice the ambiguity in this status information. If an error occurs on the indicated port, the
application program knows that one or more bytes are invalid. The program cannot know from
the status word which byte read since the last call to GetComStat is invalid.
The function returns a negative error code if the port is not open or if COMPort is invalid.

GetInQLen
int len = GetInQLen (int COMPort);
Purpose
Returns the number of characters in the input queue of the specified port. This function does not
change the input queue.

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Parameter
Input

COMPort

integer

Range 1 through 32.

integer

Number of characters in the
input queue.

Return Value
len

Parameter Discussion
The function returns an error if the port is not open or if COMPort is invalid.

GetOutQLen
int len = GetOutQLen (int COMPort);
Purpose
Returns the number of characters in the output queue of the specified port.
Parameter
Input

COMPort

integer

Range 1 through 32.

integer

Number of characters in the
output queue.

Return Value
len

Using This Function
You can use this function to ensure the output queue has emptied before you close the port. This
function has no effect on the output queue.
The function returns an error if the port is not open or if COMPort is invalid.

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GetRS232ErrorString
char *message = GetRS232ErrorString (int errorNum)
Purpose
Converts the error number returned by an RS-232 Library function into a meaningful error
message.
Parameters
Input

errorNum

integer

Error Code returned by RS-232
function.

string

Explanation of error.

Return Value
message

InstallComCallback
int status = InstallComCallback (int COMPort, int eventMask, int notifyCount,
int eventCharacter, ComCallbackPtr callbackPtr,
void *callbackData);
Note: This function is available only in the Windows version of LabWindows/CVI.
Purpose
This function allows you to install a callback function for a particular COM port. The callback
function is called whenever any of the events specified in the eventMask parameter occur on the
COM port and you allow the system to process events. The system can process events in the
following situations.
•

You have called RunUserInterface and none of your callback functions is currently
executing, or

•

You call GetUserEvent, or

•

You call ProcessSystemEvents

Only one callback function can apply for each COM port. Each call to this function for the same
COM port supersedes the previous call.
To disable callbacks for a board or device, pass 0 for the eventMask and/or callbackFunction
parameters.

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Note: The callback function may receive more than one event at a time. When using this
function at higher baud rates, some LWRS_RXCHAR events may be missed. It is
recommended to use LWRS_RECEIVE or LWRS_RXFLAG instead.
Note: Once the LWRS_RECEIVE event occurs, it is not triggered again until the input queue
falls below, and then rises back above, notifyCount bytes.
Example
notifyCount = 50; /* Wait for at least 50 bytes in queue */
eventChar
= 13; /* Wait for LF */
eventMask
= LWRS_RXFLAG | LWRS_TXEMPTY | LWRS_RECEIVE;
InstallComCallback (comport, eventMask, notifyCount,
eventChar, ComCallback, NULL);
...
/* Callback Function */
void ComCallback(int portNo, int evnetMask, void *data)
{
if (eventMask & LWRS_RXFLAG)
printf("Received specified character\n");
if (eventMask & LWRS_TXEMPTY)
printf("Transmit queue now empty\n");
if (eventMask & LWRS_RECEIVE)
printf("50 or more bytes in input queue\n");
}

Parameters
Input

COMPort

integer

Range 1 through 32.

eventMask

integer

The events upon which the callback function
is called. See the Parameter Discussion for a
list of valid events. If you want to disable
callbacks, pass 0.

notifyCount

integer

The minimum number of bytes the input
queue must contain before sending the
LWRS_RECEIVE event to the callback
function.
Valid Range: 0 to Size of Input Queue.

eventCharacter

integer

Specifies the character or byte value that
triggers the LWRS_RXFLAG event.
Valid Range: 0 to 255.

callbackPtr

ComCallbackPtr

The name of the user function that processes
the event callback.

callbackData

void *

A pointer to a user-defined four-byte value
that is passed to the callback function.

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Return Value
integer

status

Refer to error codes in Table 5-6.

Parameter Discussion
The callback function must have the following form.
void CallbackFunctionName (int COMPort, int eventMask, void *callbackData);
The eventMask and callbackData parameters are the same values that were passed to
InstallComCallback.
The events are specified using bits in the eventMask parameter. You can specify multiple event
bits in the eventMask parameter. The valid event bits are listed in the table below.
Bit

Hex Value

Com Port Event

Constant Name

0

0x0001

Any character received.

LWRS_RXCHAR

1

0x0002

Received certain character.

LWRS_RXFLAG

2

0x0004

Transmit Queue empty.

LWRS_TXEMPTY

3

0x0008

CTS changed state.

LWRS_CTS

4

0x0010

DSR changed state.

LWRS_DSR

5

0x0020

RLSD changed state.

LWRS_RLSD

6

0x0040

BREAK received.

LWRS_BREAK

7

0x0080

Line status error occurred.

LWRS_ERR

8

0x0100

Ring signal detected.

LWRS_RING

15

0x8000

notifyCount bytes in inqueue.

LWRS_RECEIVE

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The following table further describes the events.
Event Constant
Name

Description

LWRS_RXCHAR

Set when any character is received and placed in the
receiving queue.

LWRS_RXFLAG

Set when the event character is received and placed in the
receiving queue. The event character is specified in the
eventCharacter parameter of this function.

LWRS_TXEMPTY

Set when the last character in the transmission queue is sent.

LWRS_CTS

Set when the CTS (clear-to-send) line changes state.

LWRS_DSR

Set when the DSR (data-set-ready) line changes state.

LWRS_RLSD

Set when the RLSD (receive-line-signal-detect) line changes
state.

LWRS_BREAK

Set when a break is detected on input.

LWRS_ERR

Set when a line-status error occurs. Line-status errors are
CE_FRAME, CE_OVERRUN, and CE_RXPARITY.

LWRS_RING

Set to indicate that a ring indicator was detected.

LWRS_RECEIVE

Set to detect when at least notifyCount bytes are in the
input queue. Once this event has occurred, it does not
trigger again until the input queue falls below, and then rises
back above, notifyCount bytes.

OpenCom
int result = OpenCom (int COMPort, char deviceName[]);
Purpose
Opens a com port.
Parameter
Input

COMPort

integer

Range 1 through 32.

deviceName

string

Name of the COM port.

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Return Value
integer

result

Refer to error codes in Table 5-6.

Parameter Discussion
deviceName is the name of the com port in the ASCII string. For example, COM1 for com port 1
on Microsoft Windows using COMM.DRV, and /dev/ttya for com port 1 on UNIX using the
Zilog 8530 SCC serial comm driver.
If you pass a NULL pointer or an empty string for deviceName, the library uses the following
device names depending on the COM port number you have specified.
Port Number

deviceName on Windows

deviceName on UNIX

1

“COM1”

“/dev/ttya”

2

“COM2’

“/dev/ttyb”

3

“COM3”

“/dev/ttys1”

4

“COM4”

“/dev/ttys2”

and so on
Using This Function
OpenCom uses 512 bytes of the buffer for the input queue, 512 bytes for the output. The
function assumes the default baud rate, parity, stop bits, data bits, port address, and handshake
mode established through the com port configuration of the operating system. The time-out for
I/O operations is 5 seconds. Refer to the functions SetXMode, SetCTSMode, and
SetComTime if you want to change these defaults.

OpenComConfig
int result = OpenComConfig (int COMPort, char deviceName[], long baudRate,
int parity, int dataBits, int stopBits,
int inputQueueSize, int outputQueueSize);
Purpose
Opens a com port, and sets port parameters as specified. If inputQueueSize or
outputQueueSize is between 1 and 29, it is forced to 30.

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Parameters
Input

COMPort

integer

Range 1 through 32.

deviceName

string

Name of the COM port.

baudRate

long

Either 110, 150, 300, 600, 1200, 2400, 4800,
9600, 14400, 19200, 28800, 38400, 56000,
57600, 115200, 128000, or 256000.
SPARCstations do not support 14400, 28800,
56000, 57600, 115200, 128000, and 256000.
PCs do not support 150. Some PC serial
drivers do not support 115200, 128000,
and 256000.
0—no parity.
1—odd parity.
2—even parity.
3—mark parity.
4—space parity.
Either 5, 6, 7, or 8.

parity

integer

dataBits

integer

stopBits

integer

Either 1 or 2.

inputQueueSize

integer

0 selects 512. See discussion below.

outputQueueSize

integer

0 selects 512. See discussion below.

Return Value
integer

result

Refer to error codes in Table 5-6.

Parameter Discussion
deviceName is the name of the com port in the ASCII string. For example, COM1 for com port 1
on Microsoft Windows using COMM.DRV, and /dev/ttya for com port 1 on UNIX using the
Zilog 8530 SCC serial comm driver.
If you pass a NULL pointer or an empty string for deviceName, the library uses the following
device names depending on the COM port number you have specified.
Port Number

deviceName on Windows

deviceName on UNIX

1

“COM1”

“/dev/ttya”

2

“COM2’

“/dev/ttyb”

3

“COM3”

“/dev/ttys1”

4

“COM4”

“/dev/ttys2”

and so on

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Under UNIX, the inputQueueSize and outputQueueSize parameters are ignored. The serial
driver determines the queue size.
Under Windows, if you specify 0 for inputQueueSize or outputQueueSize, 512 is used. If you
specify a value between 0 and 30, 30 is used. On Windows 95 and NT, there is no maximum
limitation on the queue size. On Windows 3.1, the maximum queue size is 65535. However,
some serial drivers have a maximum of 32767 and give undefined behavior when you use a
larger queue size. It is recommended that you use a queue size no greater than 32767.
Under Windows 3.1, the baudRate value may be from 0 to 0xffff. Values below 0xff00 are
interpreted by the comm driver literally. Values from 0xff00 to 0xffff are codes defined by
the particular comm driver to represent rates higher than 0xfeff.
Under Windows 95 and NT, all baudRate values are interpreted literally by the comm driver.
Using This Function
The function disables XON/XOFF mode, and CTS hardware handshaking. The default time-out
for I/O operations is 5 seconds. Refer to the functions SetXMode, SetCTSMode, and
SetComTime if you want to change these defaults.
If the specified port is already open, OpenComConfig closes the port (see CloseCom) then
opens it again.

ReturnRS232Err
int status = ReturnRS232Err (void);
Purpose
Returns the value of rs232err.
Parameters
None
Return Value
status

LabWindows/CVI Standard Libraries

integer

Refer to error codes in
Table 5-6.

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SetComTime
int result = SetComTime (int COMPort, double timeoutSeconds);
Purpose
Sets time-out limit for input/output operations.
Parameters
Input

COMPort

integer

Range 1 through 32.

timeoutSeconds

double-precision

Time-out period for all
read/write functions.

integer

Refer to error codes in
Table 5-6.

Return Value
result

Using This Function
This function sets the time-out parameters for all read and write operations. The default value of
timeoutSeconds is 5.
For an RS-232 read operation, timeoutSeconds specifies the time allowed from the start of the
transfer to the arrival of the first byte. It also specifies the time allowed to elapse between the
arrival of any two consecutive bytes. An RS-232 read operation waits for at least the specified
amount of time for the next incoming byte before it returns a time-out error.
For an RS-232 write operation, timeoutSeconds specifies the time allowed before the first byte
is transferred to the output queue. It also specifies the time allowed between the transfer of any
two consecutive bytes to the output queue. The transfer of bytes to the output queue can become
stalled if the output queue is full and hardware or software handshaking is held off. If the holdoff is not resolved within the time-out period, the RS-232 write operation returns a time-out
error.
If the timeoutSeconds parameter is zero, it disables time-outs and the read or write functions
wait indefinitely for the operation to complete.
The function returns an error if the port is not open or parameter values are invalid.

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SetCTSMode
int result = SetCTSMode (int COMPort, int mode);
Purpose
Enables or disables hardware handshaking as described in the Hardware Handshaking section of
the RS-232 Library Function Overview.
Parameters
Input

COMPort

integer

Range 1 through 32.

mode

integer

0 to disable hardware
handshaking, non-zero to enable
hardware handshaking. See
discussion below.

integer

Refer to error codes in Table 5-6.

Return Value
result
Parameter Discussion
The following are the valid values for mode.
0—LWRS_HWHANDSHAKE_OFF—Hardware handshaking is disabled. The CTS line is ignored.
The RTS and DTR lines are raised the entire time the port is open.
1—LWRS_HWHANDSHAKE_CTS_RTS_DTR—Hardware handshaking is enabled. The CTS line
is monitored. Both the RTS and DTR lines are used for handshaking.
2—LWRS_HWHANDSHAKE_CTS_RTS—Hardware handshaking is enabled. The CTS line is
monitored. The RTS is used for handshaking. The DTR line is raised the entire time the port is
open.
Using This Function
By default, hardware handshaking is not used.
The function returns an error if the port is not open or parameter values are invalid.

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SetXMode
int result = SetXMode (int COMPort, int mode);
Purpose
Enables or disables software handshaking by enabling or disabling XON/XOFF sensitivity on
transmission and reception of data.
Parameters
Input

COMPort

integer

Range 1 through 16.

mode

integer

0 to disable, non-zero to enable.

integer

Refer to error codes in
Table 5-6.

Return Value
result

Using This Function
By default, XON/XOFF sensitivity is disabled. See the Software Handshaking section at the
beginning of this chapter.
The function returns an error if the port is not open or parameter values are invalid.

XModemConfig
int result = XModemConfig (int COMPort, double startDelay,
int maximum#ofRetries, double waitPeriod,
int packetSize);
Purpose
Sets the XModem configuration parameters for the specified com port.

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Parameters
Input

COMPort
startDelay

integer
double-precision

maximum#ofRetries
waitPeriod

integer
double-precision

Range 1 through 32.
0.0 selects the default value
10.0 seconds.
0 selects the default value 10.
0.0 selects the default value
10.0 seconds.
>5.0 is recommended.

packetSize

integer

0 selects the default value 128.

integer

Result of the XModem
configuration operation.

Return Value
result
(Less than zero)

Error code; See Table 5-6.

(Zero)

Success.

Parameter Discussion
XModemSend and XModemReceive use the baud rate, and the input/output queue sizes
specified by OpenComConfig. But they ignore the data bits, the parity and the stop bits
settings of OpenComConfig, and always use 8 bits, no parity, and one stop bit. Instead of using
the time-out value defined by the SetComTime function, XModem functions use a 1 second
time-out between data bytes.
A zero input for any parameter except COMPort sets that parameter to its default value.
startDelay sets the timing for the initial connection between the two communication parties.
When a LabWindows/CVI program assumes the role of receiver, startDelay specifies the
interval (in seconds) during which to send the initial negative acknowledgment character to the
transmitter. That character is sent every startDelay seconds, up to maximum#ofRetries times.
When a LabWindows/CVI program assumes the role of transmitter, startDelay specifies the
interval (in seconds) during which the transmitter waits for the initial negative acknowledgment.
The transmitter waits up to (startDelay*maximum#ofRetries) seconds. The default value of
startDelay is 10.0.
maximum#ofRetries sets the maximum number of times the transmitter retries sending a packet
to the receiver on the occurrence of an error condition. The default value of
maximum#ofRetries is 10.
waitPeriod sets the period of time between the transfers of two packets. When a
LabWindows/CVI program assumes the role of transmitter, it waits for up to waitPeriod seconds

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for an acknowledgment before it re-sends the current packet. When LabWindows/CVI plays the
role of receiver, it waits for up to waitPeriod seconds for the next packet after it sends out an
acknowledgment for the current packet. If it does not receive the next packet within delayPeriod
seconds, it re-sends the acknowledgment, and waits again, up to maximum#ofRetries times. The
default value of waitPeriod is 10.0.
packetSize sets the packet size in bytes. Its value must be less than or equal to the input and
queue sizes. The standard XModem protocol defines packet sizes to be 128 or 1024. If you are
using any other size, make sure the two communication parties understand each other. The
default value of packetSize is 128.
Using This Function
For transfers with a large packet size and a low baud rate, a large delay period is recommended.

XModemReceive
int result = XModemReceive (int COMPort, char fileName[]);
Purpose
Receives packets of information over the com port specified by COMPort and writes the packets
to the specified file.
Parameters
Input

COMPort

integer

Range 1 through 32.

fileName

string

Contains the pathname.

integer

Result of the XModem receive
operation.

Return Value
result
<0

Failure.

0

Success.

Using This Function
This function uses the XModem file transfer protocol. The transmitter must also follow this
protocol for this function to work properly.
The Xmodem protocol requires that the sender and receiver agree on the error checking protocol.
This agreement is negotiated at the beginning of the transfer, and can cause a significant delay.

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XModemReceive tries ((maximum#ofTries + 1) / 2) times to negotiate a CRC error check
transfer. If there is no response, it tries to negotiate a check sum transfer up to
((maximum#ofTries -1) / 2) times.
The file is opened in binary mode, and carriage returns and linefeeds are not treated as ASCII
characters. They are written to the RS-232 line, untouched.
If the size of the file being sent is not an even multiple of the packet size, the file received is
padded with NUL (0) bytes. For example, if the file being sent contains only the string HELLO,
the file written to disk contains the letters HELLO followed by (packet size - 5) bytes of zero. If
the packet size is 128, the file contains the five letters in HELLO and 123 zero bytes.
The standard XModem protocol only supports 128 and 1024 packet sizes. The sender sends an
SOH (0x01) character to indicate that the packet size is 128, or an STX character (0x02) to
indicate that the packet size is 1024. LabWindows/CVI attempts to support any packet size. As a
receiver, when LabWindows/CVI receives an STX character from the sender, it switches to
1024 packet size regardless of what the user specifies. When it receives an SOH character from
the sender, it uses the packet size specified by the user.
For transfers with a large packet size and a low baud rate, a large delay period is recommended.
Example
/* Receive the file c:\test\data from COM1 */
/* NOTE: use \\ in path name in C instead of \. */
int n;
OpenComConfig(1, 9600, 1, 8, 1, 256, 256, 0, 0);
n = XModemReceive (1, "c:\\test\\data");
if (n != 0)
FmtOut ("Error %d in receiving file",rs232err);
else
FmtOut ("File successfully received.");

XModemSend
int result = XModemSend (int COMPort, char fileName[]);
Purpose
Reads data from fileName file and sends it in packets over the com port specified by COMPort.
Parameters
Input

COMPort

integer

Range 1 through 32.

fileName

string

Contains the pathname.

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Return Value
result

integer

Result of the XModem send
operation.

<0

Failure.

0

Success.

Using This Function
The file is opened in binary mode. Carriage returns and linefeeds are not treated as ASCII
characters. They are sent to the receiver untouched.
This function uses the XModem file transfer protocol. The receiver must also follow this
protocol for this function to work properly.
If the size of the file being sent is not an even multiple of the packet size, the last packet is
padded with NUL (0) bytes. For example, if the file being sent contains only the string HELLO
and the packet size is 128, the packet of data sent contains the letters HELLO followed by
123 (packet size - 5) zero bytes.
The standard XModem protocol only supports 128 and 1024 packet sizes. The sender sends an
SOH character (0x01) to indicate that the packet size is 128, or an STX character (0x02) to
indicate that the packet size is 1024. LabWindows/CVI attempts to support any packet size. As a
sender, LabWindows/CVI sends an STX character when you specify packet size as 1024. For
any other packet size, it sends an SOH character.
For transfers with a large packet size and a low baud rate, a large delay period is recommended.

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Chapter 5

Error Conditions
If an error condition occurs during a call to any of the functions in the LabWindows/CVI RS-232
Library, the function returns an error code and the global variable rs232err contains that error
code. This code is a non-zero value that specifies the type of error that occurred. The currently
defined error codes and their meanings are given in Table 5-6.
Table 5-6. RS-232 Library Error Codes
Code

Error Message

-1

Unknown system error.

-2

Invalid port number.

-3

Port is not open.

-4

Unknown I/O error.

-5

Unexpected internal error.

-6

No serial port found.

-7

Cannot open port.

-11

Memory allocation error in creating buffers.

-13

Invalid parameter.

-14

Invalid baud rate.

-24

Invalid parity.

-34

Illegal number of data bits.

-44

Illegal number of stop bits.

-90

Bad file handle.

-91

Error in performing file I/O.

-94

Invalid count (Must be greater than or equal to 0).

-97

Invalid interrupt level.

-99

I/O operation timed out.

-104

Value must be between 0 and 255.

-114

Requested input queue size must be 0 or greater.

-124

Requested output queue size must be 0 or greater.

-151

General I/O error.

-152

Buffer parameter is NULL.

-257

Packet was sent but no acknowledgment was received.
(continues)

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Table 5-6. RS-232 Library Error Codes (Continued)
-258

Packet not sent within retry limit.

-259

Packet not received within retry limit.

-260

End of transmission character encountered when start of
data character expected.

-261

Packet number could not be read.

-262

Packet number inconsistency.

-263

Packet data could not be read.

-264

Checksum could not be read.

-265

Checksum received did not match computed
checksum.

-269

Packet size exceeds input queue size.

-300

Error opening file.

-301

Error reading file.

-302

Did not receive the initial negative acknowledgment
character.

-303

Did not receive acknowledgment after the end of
transmission character was sent.

-304

Error while writing to file.

-305

Did not receive either a start of data or end of
transmission character when expected.

-402

Transfer was canceled because the CAN character was
received.

-503

Invalid start delay.

-504

Invalid maximum number of retries.

-505

Invalid wait period.

-506

Invalid packet size.

-507

Unable to read CRC.

-508

CRC error.

The value of rs232err is zero if the most recently called RS-232 function completed
successfully. Errors above 200 occur only on XModem function calls. Errors 261 through 265
are recorded when the maximum number of retries has been exhausted in trying to receive an
XModem function packet.

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DDE Library
This chapter describes the functions in the LabWindows/CVI DDE (Dynamic Data Exchange)
Library. The DDE Library Function Overview section contains general information about the
DDE Library functions and panels. The DDE Library Function Reference section contains an
alphabetical list of function descriptions. This library is available for LabWindows/CVI for
Microsoft Windows only.

DDE Library Function Overview
The DDE Library includes functions specifically for Microsoft Windows DDE support. This
section contains general information about the DDE Library functions and panels.

The DDE Library Function Panels
The DDE Library function tree appears in Table 6-1. The first- and second-level bold headings in
the tree are the names of function classes and subclasses. Function classes and subclasses are
groups of related function panels. The third-level headings in plain text are the names of
individual function panels. Each DDE function panel generates one or more DDE function
calls. The names of functions are in bold italics to the right of the function panel name.
Table 6-1. DDE Library Function Tree
Server Functions
Register DDE Server
Server DDE Write
Advise DDE Data Ready
Broadcast DDE Data Ready
Unregister DDE Server
Client Functions
Client DDE Execute
Client DDE Read
Client DDE Write
Connect To DDE Server
Set Up DDE Hot Link
Set Up DDE Warm Link
Terminate DDE Link
Disconnect From DDE Server
Get Error String

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RegisterDDEServer
ServerDDEWrite
AdviseDDEDataReady
BroadcastDDEDataReady
UnregisterDDEServer
ClientDDEExecute
ClientDDERead
ClientDDEWrite
ConnectToDDEServer
SetUpDDEHotLink
SetUpDDEWarmLink
TerminateDDELink
DisconnectFromDDEServer
GetDDEErrorString

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DDE Clients and Servers
Interprocess communication with DDE involves a client and a server in each DDE conversation.
A DDE server can execute commands sent from another application, and send and receive
information to and from a client application under Windows. A DDE client can send commands
to a server application to be executed, and request data from a server application.
With the LabWindows/CVI DDE Library, you can write programs to act as a DDE client or
server. A detailed example using Microsoft Excel and LabWindows/CVI follows later in this
chapter to illustrate how to use the DDE Library functions.
To connect to a DDE server from a LabWindows/CVI program, you must know some
information about the application to which you would like to connect. All DDE server
applications have a name and topic that defines the connection. For example, you can connect to
Microsoft Excel as a server in two ways with the ConnectToDDEServer function from a
LabWindows/CVI program. If you want to send commands to be executed by the Excel
application, such as opening worksheets and creating charts, you should specify excel as the
server name and system as the topic name in the call to the ConnectToDDEServer
function. However, if you want to send data to an Excel spreadsheet, you should specify excel
as the server name and the filename of the worksheet that is already loaded in Excel as the topic
name.
If your program acts as a DDE server, where other Windows applications will be sending and
receiving commands and data, you need to call the RegisterDDEServer function in your
program. The RegisterDDEServer function establishes your program as a valid DDE server
so that other applications can connect to it and exchange information. The server callback
function will then be invoked as discussed in the following section.

The DDE Callback Function
Callback functions provide the mechanism for sending and receiving data to and from other
applications through DDE. Similar to the method in which a callback function responds to user
interface events from your User Interface Library object files, a DDE callback function responds
to incoming DDE information.
As shown in Table 6-2, a callback function in a client application can respond to only two types
of DDE messages: DDE_DISCONNECT and DDE_DATAREADY. After you set up a warm link
or hot link (also called an advisory loop) to another application, the callback function defined in
the SetUpDDEHotLink or SetUpDDEWarmLink function will be called whenever the data
values change in the other application, or when the other application is closed.

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DDE callback functions used in a program that acts as a DDE server can be triggered in a
number of ways from client applications. Whenever a client application attempts to connect to
your server program or requests information from your program, the callback function in your
program is executed to process the request. The parameter prototypes for the DDE callback
functions in LabWindows/CVI are defined below:
int CallbackFunction (int handle, char *topicName,
char *itemName, int xType, int dataFmt,
int dataSize, void *dataPtr,
void *callbackData);

Parameters
Input

Note:

handle

The conversation handle which uniquely identifies the client
server connection.

topicName

The server application triggering the callback.

itemName

The data item within the server application that triggers the
callback. Exception: When xType is DDE_EXECUTE,
itemName represents the command string from the client
program.

xtype

The transaction type (see Table 6-2).

dataFmt

The format of the data being transmitted.

dataSize

The number of bytes in the data. May actually be greater
than the number of bytes transmitted. It is recommended
that you encode size information in your data.

dataPtr

Points to the transmitted data.

callbackData

A user-defined data value.

The value of the dataSize parameter is greater than or equal to the actual size of
the data. It is recommended that you encode size information in your data.

Return Value
The callback function should return 1 to indicate success or 0 to indicate failure or rejection of
the requested action.
Transaction Types
All of the DDE transaction types (xType) that can trigger a callback function are listed in
Table 6-2.

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Table 6-2. DDE Transaction Types (xType)
xType
DDE_CONNECT

Server

Client

When ?

Y

N

When a new client requests a
connection.

DDE_DISCONNECT

Y

Y

When conversation partner quits.

DDE_DATAREADY

Y

Y

When conversation partner sends
data.

DDE_REQUESTDATA

Y

N

When client requests data.

DDE_ADVISELOOP

Y

N

When client requests advisory loop.

DDE_ADVISESTOP

Y

N

When client terminates request for
advisory loop.

DDE_EXECUTE

Y

N

When client requests execution of a
command.

Refer to the description for RegisterDDEServer and ConnectToDDEServer for more
information about the DDE callback function.

DDE Links
Whenever a client program needs to be informed of changes to the value of a particular data item
in the server application, a DDE data link is required. You can establish a DDE data link in
LabWindows/CVI by calling the SetUpDDEWarmLink or SetUpDDEHotLink functions.
Whenever the data value changes, the client callback function is triggered, and the data is
available in the dataPtr parameter.
Within one client-server connection, there can be multiple data links, each applying to a different
data item. For example, you can establish a link between your LabWindows/CVI program and a
particular cell in Excel. The data item to which the link applies is specified in the itemName
parameter in the call to SetUpDDEWarmLink or SetUpDDEHotLink functions.
As defined in Windows, warm and hot links differ in that under a warm link the client is merely
alerted when the data value changes, whereas under a hot link the data is actually sent.
LabWindows/CVI makes no distinction between warm links and hot links. In both cases, your
client application receives the data through the client callback function when the data value
changes. (If a warm link is in effect, LabWindows/CVI requests and receives the data from the
server before the callback function is called.) The SetUpDDEWarmLink and
SetUpDDEHotLink functions are provided because some DDE server applications offer only
one type of link.

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A DDE Library Example Using Microsoft Excel and LabWindows/CVI
LabWindows/CVI includes a sample program called ddedemo.prj that uses DDE to send data
to Microsoft Excel. The example program can be found in the samples\ddetcp directory.
The following discussion outlines the process required to open an Excel worksheet file, send data
over DDE, and setup a DDE link with one of the cells in the worksheet from a LabWindows/CVI
program. Start Excel and load the worksheet file called LWCVI.XLS. The sample program
performs the following operations.
1. Connects to the Microsoft Excel worksheet as a client.
The function, ConnectToDDEServer, with excel as the server name and LWCVI.XLS
as the topic name, establishes a connection with the worksheet. The Callback Function
Pointer, ClientCallback, identifies the function which will process the DDE
transactions generated from this particular conversation.
2. Establishes a DDE warm link with a particular cell in the Excel worksheet.
The function, SetUpDDEWarmLink, with the cell address (R5C2) as the item name,
establishes a DDE link between the cell in the worksheet. Thereafter, whenever the value of
cell B5 (row 5, column 2) changes, Excel sends information to LabWindows/CVI by
triggering the clientCallbackFunction.
3. Sends data to the Excel worksheet from LabWindows/CVI.
After the data is formatted as a string, it is sent to Excel using the ClientDDEWrite
function with the Excel cell region (R1C2:R50C2) as the item name, and the character
array, containing 50 elements, as the buffer pointer.
4. The callback function responds to DDE transactions from the Excel worksheet.
The callback function automatically returns the following information:
handle—The conversation which triggered the callback (multiple DDE conversations can be
processed by the same callback function).
item name—The cell(s) involved.
topic name—The Excel system or file in Excel involved.
transaction type—Either DDE_DATAREADY or DDE_DISCONNECT.
data format—CF_TEXT in this case.
data size—Number of bytes in the data.
data pointer—Pointer to the data.
callback data—User defined (NULL in this case).

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When the DDE_DATAREADY transaction is received in the callback function, a numeric
display is updated by passing the data pointer value to a numeric control on the UIR file.
When the DDE event is DDE_DISCONNECT, the DisconnectFromDDEServer
function ends the DDE conversation and program execution is halted.

DDE Library Function Reference
AdviseDDEDataReady
int status = AdviseDDEDataReady (unsigned int conversationHandle,
char itemName[], unsigned int dataFormat,
void *dataPointer, unsigned int dataSize,
unsigned int timeout);
Purpose
Called by a server to write data to a DDE client application. The server should call this only
when the value of a data item changes, and a warm or hot link has been established for the data
item.
Parameters
Input

conversationHandle

unsigned integer

Uniquely identifies the
conversation.

itemName

string

Uniquely identifies the output
item; for example, system.

dataFormat

unsigned integer

Valid data format; for example,
CF_TEXT.

dataPointer

void pointer

Pointer to buffer holding data.

dataSize

unsigned integer

Number of bytes in data. Must
be 0 if dataPointer is NULL.
Limited to 64 kbytes under
Windows 3.1 and Windows 95.

timeout

unsigned integer

Timeout in ms.

integer

Refer to error codes in
Table 6-3.

Return Value
status

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Parameter Discussion
dataFormat must be a valid data format recognized by Microsoft Windows. The following are
the valid data formats supported by Microsoft Windows:
CF_TEXT

CF_PALETTE

CF_BITMAP

CF_PENDATA

CF_METAFILEPICT

CF_RIFF

CF_SYLK

CF_WAVE

CF_DIF

CF_OWNERDISPLAY

CF_TIFF

CF_DSPTEXT

CF_OEMTEXT

CF_DSPBITMAP

CF_DIB

CF_DSPMETAFILEPICT

The Microsoft Windows 3.x Programmer's Reference contains an in-depth discussion of DDE
programming and meaning of each data format type.
Using This Function
This function allows your program, acting as a DDE server, to send data to a client that has set
up a hot or warm link.
When a hot or warm link is set up, your server callback function receives a DDE_ADVISELOOP
transaction type (xType) for a particular data object (identified by itemName). When the hot or
warm link is terminated, your server callback function receives a DDE_ADVISESTOP
transaction type for the data object.
During the period when the hot or warm link is in effect, your server program is responsible for
notifying the client whenever the value of the data object changes. When the data object's value
changes, you can call this function, AdviseDDEDataReady, or
BroadcastDDEDataReady.
AdviseDDEDataReady differs from BroadcastDDEDataReady in that you specify a
particular conversation with a client. AdviseDDEDataReady sends the data only to the
specified client, even if other clients have hot or warm links to the same item.
AdviseDDEDataReady sends the data without invoking your server callback function.
However, if there are other clients with warm links to the same item, they are all notified that
new data is available. If they request the new data, your server callback function is invoked with
the DDE_REQUESTDATA message. If you do not want to send the data to those other clients,
you must write your server callback function so that it does not call ServerDDEWrite in this
case.
If you pass NULL (0) as the dataPointer and 0 as the dataSize, no data is sent to the specified
client. Instead, all clients with warm links to the item are notified. If they request the new data,
your server callback function is invoked with the DDE_REQUESTDATA message, and you can
use the ServerDDEWrite function to send the data in response.
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If successful, this function returns the number of bytes sent. Otherwise, this function returns a
negative error code. See the help for the status control for the error code values.
Note: Your program should not call AdviseDDEDataReady in a tight loop because the
iterations will compete with user interface events for the CPU time. You should use
this function sparingly, and only when the value of the hot- or warm-linked data object
changes. In cases when large data objects are to be returned from the server, your
program should only call AdviseDDEDataReady when the user interface is not
busy.
See Also
RegisterDDEServer, SetUpDDEHotLink, SetUpDDEWarmLink,
BroadcastDDEDataReady

BroadcastDDEDataReady
int status = BroadcastDDEDataReady (char serverName[], char itemName[],
char topicName[], unsigned int dataFormat,
void *dataPointer, unsigned int dataSize)
Purpose
Called by a server to send, to send data to all clients that have set up hot or warm links on the
specified topic and item.
Parameters
Input

serverName

string

Identifies the server from which to send the data.

topicName

string

Identifies the topic with which the data is
associated.

itemName

string

Identifies the item with which the data is
associated.

dataFormat

unsigned
integer

Valid data format; for example, CF_TEXT.

dataPointer

void pointer

Pointer to buffer holding data.

dataSize

unsigned
integer

Number of bytes in data. Limited to 64 KB on
Windows 3.1 and Windows 95.

integer

Refer to error codes in Table 6-3.

Return Value
status

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Parameter Discussion
serverName, topicName, and itemName must be strings of length from 1 to 255. They are used
without regard to case.
Using this Function
This function allows your program, acting as a DDE server, to send data to all clients that have
set up hot or warm links on the specified topic and item.
When a hot or warm link is set up, your server callback function receives a DDE_ADVISELOOP
transaction type (xType) for a particular data object (identified by itemName). When the hot or
warm link is terminated, your server callback function receives a DDE_ADVISESTOP
transaction type for the data object.
During the period when the hot or warm link is in effect, your server program is responsible for
notifying the client whenever the value of the data object changes. When the data object's value
changes, your server program should call either of the following functions,
BroadcastDDEDataReady or AdviseDDEDataReady.
BroadcastDDEDataReady differs from AdviseDDEDataReady in that it is not restricted
to a particular client. BroadcastDDEDataReady sends the data automatically to all clients
with hot links to the item. BroadcastDDEDataReady notifies all clients with warm links to
the item. For each warm-linked client that requests the data, your server callback function is
invoked with the DDE_REQUESTDATA message. You must call ServerDDEWrite in the
callback to send the data.
When successful, this function returns the number of bytes sent. Otherwise, this function returns
a negative error code. Consult the table at the end of this chapter to see the error code values.
Note: Your program should not call this function within a tight loop, because it will compete
with user interface events for the CPU time. This function should be used sparingly,
and only when the value of the hot or warm linked data object changes. In cases when
large data objects are to be returned from the server, it should only be called when the
user interface is not busy.
See Also
RegisterDDEServer, SetUpDDEHotLink, SetUpDDEWarmLink,
AdviseDDEDataReady,

ClientDDEExecute
int status = ClientDDEExecute (unsigned int conversationHandle,
char commandString[], unsigned int timeout);

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Purpose
Called by client to send a command to be executed by a DDE server application.
Parameters
Input

conversationHandle unsigned integer

Uniquely identifies the
conversation.

commandString

string

Command to be executed by
the server application.

timeout

unsigned integer

Timeout in ms.

integer

Refer to error codes in
Table 6-3.

Return Value
status

Parameter Discussion
The commandString represents a valid command sequence for the server application to execute.
Refer to the command function reference manual for the application to which you are connecting
for more information on the commands supported.
See Also
ConnectToDDEServer, ClientDDERead, ClientDDEWrite

ClientDDERead
int status = ClientDDERead (unsigned int conversationHandle, char itemName[],
unsigned int dataFormat, void *dataBuffer,
unsigned int dataSize, unsigned int timeout);
Purpose
Called by client to read data from a DDE server application.
Parameters
Input

conversationHandle

unsigned integer

A handle uniquely identifies the
conversation.

itemName

string

Uniquely identifies the output
item; for example, system.

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Output

DDE Library

dataFormat

unsigned integer

Valid data format; for example,
CF_TEXT.

dataSize

unsigned integer

Number of bytes to read.
Limited to 64 KB under
Windows 3.1 and Windows 95.

timeout

unsigned integer

Timeout in ms.

dataBuffer

void pointer

Buffer in which to receive data.

integer

Refer to error codes in
Table 6-3.

Return Value
status

Parameter Discussion
dataFormat must be a valid data format recognized by Microsoft Windows. The following are
the valid data formats supported by Microsoft Windows:
CF_TEXT

CF_PALETTE

CF_BITMAP

CF_PENDATA

CF_METAFILEPICT

CF_RIFF

CF_SYLK

CF_WAVE

CF_DIF

CF_OWNERDISPLAY

CF_TIFF

CF_DSPTEXT

CF_OEMTEXT

CF_DSPBITMAP

CF_DIB

CF_DSPMETAFILEPICT

Refer to Microsoft programmers' documention for Windows 3.x for an in-depth discussion of
DDE programming and meaning of each data format type.
status returns a positive number representing the number of bytes that were successfully read. A
negative number corresponds to the error code.
See Also
ConnectToDDEServer, ClientDDEWrite

ClientDDEWrite
int status = ClientDDEWrite (unsigned int conversationHandle, char itemName[],
unsigned int dataFormat, void *dataPointer,
unsigned int dataSize, unsigned int timeout);
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Purpose
Called by client to write data to a DDE server application.
Parameters
Input

conversationHandle

unsigned integer

Uniquely identifies the
conversation.

itemName

string

Uniquely identifies the output
item; for example, system.

dataFormat

unsigned integer

Valid data format; for example,
CF_TEXT.

dataPointer

void pointer

Buffer holding data.

dataSize

unsigned integer

Number of bytes to write.
Limited to 64 KB under
Windows 3.1 and Windows 95.

timeout

unsigned integer

Timeout in ms.

integer

Refer to error codes in
Table 6-3.

Return Value
status

Parameter Discussion
dataFormat must be a valid data format recognized by Microsoft Windows. The following are
the valid data formats supported by Microsoft Windows:
CF_TEXT

CF_PALETTE

CF_BITMAP

CF_PENDATA

CF_METAFILEPICT

CF_RIFF

CF_SYLK

CF_WAVE

CF_DIF

CF_OWNERDISPLAY

CF_TIFF

CF_DSPTEXT

CF_OEMTEXT

CF_DSPBITMAP

CF_DIB

CF_DSPMETAFILEPICT

Refer to Microsoft programmers' documention for Windows 3.x for an in-depth discussion of
DDE programming and meaning of each data format type.
status returns a positive number representing the number of bytes that were successfully read. A
negative number corresponds to the error code.

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See Also
ConnectToDDEServer, ClientDDERead

ConnectToDDEServer
int status = ConnectToDDEServer (unsigned int *conversationHandle,
char serverName[], char topicName[],
ddeFuncPtr clientCallbackFunction,
void *callbackData);
Purpose
Establishes a connection (conversation) between your program and a named server on a given
topic name.
Parameters
Input

serverName

string

Name of the server application.

topicName

string

Specifies the type of
conversation with the server.

clientCallbackFunction DDE function
pointer
Output

Pointer to the user callback
function.

callbackData

void pointer

User-defined data.

conversationHandle

unsigned integer

Uniquely identifies the
conversation.

integer

Refer to error codes in
Table 6-3.

Return Value
status

Parameter Discussion
The conversationHandle returns an integer value that uniquely represents a conversation
between a server and a client.
serverName and topicName must be strings of length from 1 to 255. They are used without
regard to case.
Each server application defines its own set of valid topic names. Refer to the command function
reference manual for the server application. A client and a server can have multiple connections
as long as they are under different topic names.

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clientCallbackFunction defines a callback function through which all messages from the server
will be routed.
The callback function must be of the following form:
int (*ddeFuncPtr) (int handle, char *topicName, char *itemName,
int xType, int dataFmt, int dataSize,
void*dataPtr, void *callbackData);
The xType (transaction type) parameter specifies the type of message received from the server.
The clientCallbackFunction can receive only two transaction types: DDE_DISCONNECT and
DDE_DATAREADY.
DDE_DISCONNECT—Received when a server is requesting the termination of a connection, or
when Windows terminates the connection due to an internal error.
DDE_DATAREADY—Received when you have already set up a hot or warm link by calling
SetUpDDEHotLink or SetUpDDEWarmLink, and the server notifies you that new data is
available. (If the server program uses the LabWindows/CVI DDE Library, it notifies you by
calling AdviseDDEDataReady or BroadcastDDEDataReady.) The data is received in
the callback in the dataPtr parameter. The topicName, itemName, dataFmt, dataSize, and
dataPtr parameters contain significant data. The itemName can specify an object to which the
data refers. For example, in Excel, the item name specifies a cell. The dataFmt is one of the
Windows-defined data types, for example, CF_TEXT. The dataSize specifies the number of
bytes in the data pointed to by dataPtr.
Note: The dataSize value is the value LabWindows/CVI receives from Microsoft Windows.
This value can be larger than the actual number of bytes written by the client.
Note: The callback function should return TRUE if the message can be processed
successfully. Otherwise, it should return FALSE. The callback function should be
short and return as soon as possible.
callbackData is a four-byte value that will be passed to the callback function each time it is
called for this client.
You can define the meaning of the callback data. For example, you can use the callback data as a
pointer to a data object that you need to access in the callback function. In this way, you would
not need to declare the data object as a global variable.
If you do not want to use the callback data, you can pass zero.
Note: In the case of DDE_DISCONNECT, the value of callbackData is undefined.
See Also
DisconnectFromDDEServer, RegisterDDEServer

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DisconnectFromDDEServer
int status = DisconnectFromDDEServer (unsigned int conversationHandle);
Purpose
Disconnects your client program from a server application.
Parameters
Input

conversationHandle

unsigned integer

Uniquely identifies the
conversation.

integer

Refer to error codes in
Table 6-3.

Return Value
status

Note: This function ends a conversation between a client and server corresponding to the
conversationHandle that was passed. Remember that there can be more than one
conversation between a client and a server.
See Also
ConnectToDDEServer, RegisterDDEServer

GetDDEErrorString
char *message = GetDDEErrorString (int errorNum)
Purpose
Converts the error number returned by a DDE Library function into a meaningful error message.
Parameters
Input

errorNum

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integer

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Status returned by a
DDE function.

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Chapter 6

Return Value
string

message

Explanation of error.

RegisterDDEServer
int status = RegisterDDEServer (char serverName[],
ddeFuncPtr serverCallbackFunction,
void *callbackData);
Purpose
Registers your program as a valid DDE server, allowing other Windows applications to connect
to it for interprocess communication.
Parameters
Input

serverName

string

Name of the server application.

serverCallbackFunction DDE function
pointer
callbackData

void pointer

Pointer to the user callback
function.
Pointer to the user data.

Return Value
status

integer

Refer to error codes in
Table 6-3.

Parameter Discussion
serverName must be a string of length from 1 to 255. It is used without regard to case.
The serverCallbackFunction is the name of the callback function that will be invoked to
process client requests.
The callback function must be of the following form:
int (*ddeFuncPtr) (int handle, char *topicName, char *itemName,
int xType, int dataFmt, int dataSize,
void *dataPtr, void *callbackData);
The xType (transaction type) parameter specifies the type of request received from the client.
The following transaction types are supported:
DDE_CONNECT

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DDE_DISCONNECT
DDE_DATAREADY
DDE_REQUEST
DDE_ADVISELOOP
DDE_ADVISESTOP
DDE_EXECUTE
DDE_CONNECT—This transaction type is received when a client is requesting a connection.
The topicName parameter specifies the connection topic. The set of valid topic names is defined
by the server and can be used in different ways. For example, Excel uses the topic name to
specify the file on which the client requests to operate. A client can have multiple connections to
the same server as long as there is a different topic name for each connection.
DDE_DISCONNECT—Received when a client is requesting the termination of a connection, or
when Windows terminates the connection due to an internal error.
DDE_DATAREADY—Received when the client has sent data via DDE to the server. The
topicName, itemName, dataFmt, dataSize, and dataPtr parameters contain significant data.
The itemName can specify an object to which the data refers. For example, in Excel, the item
name specifies a cell. The dataFmt is one of the Windows-defined data types, for example,
CF_TEXT. The dataSize specifies the number of bytes in the data pointed to by dataPtr.
Note: The dataSize value is the value LabWindows/CVI receives from Microsoft Windows.
This value can be larger than the actual number of bytes written by the client.
DDE_REQUEST—Received when the client is requesting that data be sent to it via DDE. The
itemName can specify an object to which the data refers. For example, in Excel, the item name
specifies a cell. The dataFmt is one of the Windows-defined data types, for example,
CF_TEXT.
DDE_ADVISELOOP—Received when the client is requesting a hot or warm link (advisory loop)
on a specific item. When a hot or warm link is in effect, the server is supposed to notify the
client whenever the specified item changes value. The server notifies the client of the change in
value by calling the function AdviseDDEDataReady or BroadcastDDEDataReady. The
itemName and dataFmt parameters contain significant values. The itemName can specify an
object to which the data item refers. For example, in Excel, the item name specifies a cell. The
dataFmt is one of the Windows-defined data types, for example, CF_TEXT.
DDE_ADVISESTOP—Received when the client is requesting the termination of an advisory
loop. The itemName contains the same value that was used to set up the advisory loop.
DDE_EXECUTE—Received when the client requests the execution of a command. The
itemName parameter contains the command string. The set of valid command strings is defined
by the server. For example, Excel uses "[Save()]" to save a file.
Using This Function

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This function registers your program as a DDE server with the specified name. Clients
attempting to connect to your program must use the specified name. Thereafter, all requests by
the client will be routed through the specified serverCallbackFunction.
You can register your program as a DDE server multiple times as long as you specify different
server names.
Note: The callback function should return TRUE if the request is successful else return
FALSE. The callback function should be short and should return as soon as possible.
callbackData is a four-byte value that will be passed to the callback function each time it is
called for this server.
You can define the meaning of the callback data. The following are examples of how the
callback data can be used:
1. You can register your program as a DDE server multiple times under different names. For
instance, you can use the same callback function for all of the server instances by using the
callback data to differentiate between them.
2. You can use the callback data to point to a data object that you need to access in the callback
function. In this way, you would not need to declare the data object as a global variable.
If you do not want to use the callback data, you can pass zero.
Note: In the case of DDE_DISCONNECT, the value of callbackData is undefined.
See Also
ConnectToDDEServer, UnregisterDDEServer

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ServerDDEWrite
int status = ServerDDEWrite (unsigned int conversationHandle, char itemName[],
unsigned int dataFormat, void *dataPointer,
unsigned int dataSize, unsigned int timeout);
Purpose
Writes data to a DDE client application when it requests data.
Parameters
Input

conversationHandle

unsigned integer

Uniquely identifies the
conversation.

itemName

string

Uniquely identifies the output
item; for example, system.

dataFormat

unsigned integer

Valid data format; for example,
CF_TEXT.

dataPointer

void pointer

Buffer holding data.

dataSize

unsigned integer

Number of bytes to write.
Limited to 64 KB under
Windows 3.1 and Windows 95.

timeout

unsigned integer

Timeout in ms.

integer

Refer to error codes in
Table 6-3.

Return Value
status

Parameter Discussion
dataFormat must be a valid data format recognized by Microsoft Windows. The following are
the valid data formats supported by Microsoft Windows:
CF_TEXT

CF_PALETTE

CF_BITMAP

CF_PENDATA

CF_METAFILEPICT

CF_RIFF

CF_SYLK

CF_WAVE

CF_DIF

CF_OWNERDISPLAY

CF_TIFF

CF_DSPTEXT

CF_OEMTEXT

CF_DSPBITMAP

CF_DIB

CF_DSPMETAFILEPICT

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Refer to Microsoft programmers' documention for Windows 3.x for an in-depth discussion of
DDE programming and meaning of each data format type.
Using This Function
This function allows your program, acting as a DDE server, to send data to a client. You should
call this function only when your serverCallbackFunction receives transaction type (xType) of
DDE_REQUESTDATA.
If you call the function at any other time, the data is stored until the client requests data. If you
call the function multiple times on the same conversation before the client requests the data, each
new data set is appended to the buffer containing the stored data.
If the client has set up a hot or warm link and you need to send data other than in response to a
DDE_REQUESTDATA transaction, use the AdviseDDEDataReady or
BroadcastDDEDataReady function.
If successful, this function returns the number of bytes written. Otherwise, this function returns a
negative error code.
See Also
RegisterDDEServer, AdviseDDEDataReady

SetUpDDEHotLink
int status = SetUpDDEHotLink (unsigned int conversationHandle, itemName[],
unsigned int dataFormat,
unsigned int timeout);
Purpose
Sets up a hot link (advisory loop) between the client and the server. The function returns zero for
success and a negative error code for failure.
Parameters
Input conversationHandle

unsigned integer

Uniquely identifies the conversation.

itemName

string

Uniquely identifies the output item; for
example, system.

dataFormat

unsigned integer

Valid data format; for example,
CF_TEXT.

timeout

unsigned integer

Timeout in ms.

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Return Value
integer

status

Refer to error codes in Table 6-3.

Parameter Discussion
The itemName represents the information in the server application where the DDE link is
established. For example, the item name could represent an Excel range of cells by using the
range description R1C1:R10C10.
Note: To the client, LabWindows/CVI does not distinguish between a hot link and a warm
link. For both types of links, the clientCallbackFunction is called with a transaction
type of DDE_DATAREADY when the data item is changed at the server site, and the new
data is available in the dataPtr parameter of the callback function. LabWindows/CVI
has two different functions for setting up a warm link or hot link in case some
applications only accept one or the other kind of link.
See Also
RegisterDDEServer, SetUpDDEWarmLink

SetUpDDEWarmLink
int status = SetUpDDEWarmLink (unsigned int conversationHandle,
char itemName[], unsigned int dataFormat,
unsigned int timeout);
Purpose
Sets up a warm link (advisory loop) between the client and the server. The function returns zero
for success and a negative error code for failure.
Parameters
Input

conversationHandle unsigned integer Uniquely identifies the conversation.
string
Uniquely identifies the output item; for
itemName
example, system.
dataFormat

unsigned integer Valid data format; for example,
CF_TEXT.

timeout

unsigned integer Timeout in ms.

Return Value
status

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integer

Refer to error codes in Table 6-3.

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Parameter Discussion
The itemName represents the information in the server application where the DDE link is
established. For example, the item name could represent an Excel range of cells by using the
range description R1C1:R10C10.
Note: To the client, LabWindows/CVI does not distinguish between a hot link and a warm
link. For both types of links, the clientCallbackFunction is called with a transaction
type of DDE_DATAREADY when the data item is changed at the server site, and the new
data is available in the dataPtr parameter of the callback function. LabWindows/CVI
has two different functions for setting up a warm link or hot link in case some
applications only accept one or the other kind of link.
See Also
RegisterDDEServer, SetUpDDEHotLink

TerminateDDELink
int status = TerminateDDELink (unsigned int conversationHandle,
char itemName[], unsigned int dataFormat,
unsigned int timeout);
Purpose
Lets your program, acting as a DDE client, terminate an advisory link, previously set up with the
server either through SetUpDDEWarmLink or SetUpDDEHotLink.
This function returns zero for success or a negative error code for failure.
Parameters
Input conversationHandle unsigned integer Uniquely identifies the conversation.
string
Uniquely identifies the output item; for
itemName
example, system.
dataFormat

unsigned integer Valid data format; for example, CF_TEXT.

timeout

unsigned integer Timeout in ms.

Return Value
status

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Refer to error codes in Table 6-3.

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UnregisterDDEServer
int status = UnregisterDDEServer (char serverName[]);
Purpose
Unregisters your application program as a DDE server.
Parameters
Input

serverName

string

Name of the server application.

integer

Refer to error codes in
Table 6-3.

Return Value
status

See Also
RegisterDDEServer

Error Conditions
If an error condition occurs during a call to any of the functions in the LabWindows/CVI DDE
Library, the status return value contains the error code. This code is a non-zero value that
specifies the type of error that occurred. Error code return values are negative numbers. The
currently defined error codes and their associated meanings are shown in Table 6-3.

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Table 6-3. DDE Library Error Codes
Code
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
-11
-12
-13
-14
-15
-16
-17
-18
-19
-20
-21
-22
-23
-24
-25
-26
-27
-28
-29
-30
-31
-32
-33

Error Message
kDDE_NoError
-kDDE_UnableToRegisterService
-kDDE_ExistingServer
-kDDE_FailedToConnect
-kDDE_ServerNotRegistered
-kDDE_TooManyConversations
-kDDE_ReadFailed
-kDDE_WriteFailed
-kDDE_ExecutionFailed
-kDDE_InvalidParameter
-kDDE_OutOfMemory
-kDDE_TimeOutErr
-kDDE_NoConnectionEstablished
-kDDE_FailedToSetUpHotLink
-kDDE_FailedToSetUpWarmLink
-kDDE_GeneralIOErr
-kDDE_AdvAckTimeOut
-kDDE_Busy
-kDDE_DataAckTimeOut
-kDDE_DllNotInitialized
-kDDE_DllUsage
-kDDE_ExecAckTimeOut
-kDDE_DataMismatch
-kDDE_LowMemory
-kDDE_MemoryError
-kDDE_NotProcessed
-kDDE_NoConvEstablished
-kDDE_PokeAckTimeOut
-kDDE_PostMsgFailed
-kDDE_Reentrancy
-kDDE_ServerDied
-kDDE_SysError
-kDDE_UnadvAckTimeOut
-kDDE_UnfoundQueueId

Note: Error codes from -16 to -33 are native DDEML errors which correspond to Windows
DDE error codes starting from 0x4000.

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Chapter 7
TCP Library
This chapter describes the functions in the LabWindows/CVI TCP (Transmission Control
Protocol) Library. The TCP Library Function Overview section contains general information
about the TCP Library functions and panels. The TCP Library Function Reference section
contains an alphabetical list of function descriptions.
In order to use this library in Microsoft Windows, a version of WINSOCK.DLL has to be present.
The DLL comes with the program that drives the network card.

TCP Library Function Overview
This section contains general information about the TCP Library functions and network
communication using TCP. TCP Library functions provide a platform-independent interface to
the reliable, connection-oriented, byte-stream, network communication protocol.

The TCP Library Function Panels
The first- and second-level bold headings in the tree are the names of function classes and
subclasses. Function classes and subclasses are groups of related function panels. The
third-level headings in plain text are the names of individual function panels. Each TCP Library
function panel generates one TCP Library function call. The names of the corresponding TCP
Library function calls appear in bold italics to the right of the function panel names. The TCP
Library function tree appears in Table 7-1.
Table 7-1. The TCP Library Function Tree
Server Functions
Register TCP Server
Server TCP Read
Server TCP Write
Unregister TCP Server
Disconnect TCP Client
Client Functions
Connect To TCP Server
Client TCP Read
Client TCP Write
Disconnect From TCP Server
Get Error String

© National Instruments Corporation

RegisterTCPServer
ServerTCPRead
ServerTCPWrite
UnregisterTCPServer
DisconnectTCPClient
ConnectToTCPServer
ClientTCPRead
ClientTCPWrite
DisconnectFromTCPServer
GetTCPErrorString

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TCP Clients and Servers
Network communication using the TCP library involves a client and a server in each connection.
A TCP server can send and receive information to and from a client application through a
network. A TCP client can send and request data to and from a server application. Once
registered, a server waits for clients to request connection to it. A client, however, can only
request connection to a pre-existing server.
With the LabWindows/CVI TCP Library, you can write programs to act as a TCP client or
server. Under Windows, you cannot run both a server and a client on the same computer. The
procedure for writing a program using TCP is similar to the procedure followed for using DDE.
Refer to the sample program discussion in Chapter 6, DDE Library. Two additional sample
programs, TCPSERV.PRJ and TCPCLNT.PRJ, provide some guidelines on structuring your
TCP programs as a server or client. These programs are provided as templates only, and will
require modification for operation on your machine.
To connect to a TCP server from a LabWindows/CVI program, you must have some information
about the application to which you would like to connect. All TCP server applications must run
on a specified host, which either has a known host name (for example, aaa.bbb.ccc) or a
known IP address (for example, 123.456.78.90) associated with it. In addition, each server
specifies its own unique port number. These two pieces of information identify different servers
either on the same machine or on different machines. Before any client program can connect to a
server, it has to know the host name and server port number.
If your program is to act as a TCP server, you must call the RegisterTCPServer function in
your program. The RegisterTCPServer function establishes your program as the server
associated with a port number on the local host. Client applications can connect to your program
by using either the host name (where the server application is currently running) or the IP
address, and the port number associated with the server application. The callback function is
invoked whenever the conversation partner requests communication. This is discussed in the
following section.

The TCP Callback Function
Callback functions provide the mechanism for receiving notification of connection, connection
termination, and data availability. Similar to the method in which callback function responds to
user interface events from your User Interface Library object files, a TCP callback function
responds to incoming TCP messages and information.
As shown in Table 7-2, a callback function can respond to three types of TCP messages:
TCP_CONNECT, TCP_DISCONNECT, and TCP_DATAREADY.
TCP callback functions, used in a program acting as a TCP server, can be triggered in a number
of ways from client applications. Whenever a client application attempts to connect to your
server program or requests information from your program, the callback function in your

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program is invoked to process the request. The parameter prototypes for the TCP callback
functions in LabWindows/CVI are defined below:
int CallbackFunction (int handle, int xType, int errCode,
void *callbackData);

where
handle represents the conversation handle
xType represents the transaction type (see table below)
errCode for TCP_DISCONNECT, is negative if the connection is being terminated due to an
error
callbackData is a user-defined data value.
All of the TCP transaction types (xType) that can trigger a callback function are listed in
Table 7-2.
Table 7-2. TCP Transaction Types (xType)
xType
TCP_CONNECT

Server

Client

When ?

Y

N

When a new client requests for
connection.

TCP_DISCONNECT

Y

Y

When conversation partner quits.

TCP_DATAREADY

Y

Y

When conversation partner sends
data.

Refer to the descriptions for RegisterTCPServer and ConnectToTCPServer for more
information about the TCP callback function.

TCP Library Function Reference
ClientTCPRead
int status = ClientTCPRead (unsigned int conversationHandle, void *dataBuffer,
unsigned int dataSize, unsigned int timeout);
Purpose
Reads data from a TCP server application when it contains data that is ready for TCP network
transmission.

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Parameters
Input

conversationHandle

unsigned integer

Uniquely identifies the
conversation.

dataBuffer

void pointer

Buffer in which to receive data.

dataSize

unsigned integer

Maximum number of bytes to
read.

timeout

unsigned integer

Timeout in ms.

integer

Returns the number of bytes
read, or a negative error code if
an error occurs; Refer to error
codes in Table 7-3.

Return Value
status

See Also
ConnectToTCPServer, ClientTCPWrite

ClientTCPWrite
int status = ClientTCPWrite (unsigned int conversationHandle, void *dataPointer,
int dataSize, unsigned int timeout);
Purpose
Writes data to a TCP server application.
Parameters
Input

conversationHandle

unsigned integer

Uniquely identifies the
conversation.

dataPointer

void pointer

Buffer holding data.

dataSize

unsigned integer

Number of bytes to write.

timeout

unsigned integer

Timeout in ms.

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Return Value
integer

status

Returns the number of bytes
written, or a negative error code
if an error occurs; Refer to error
codes in Table 7-3.

See Also
ConnectToTCPServer, ClientTCPRead

ConnectToTCPServer
int status = ConnectToTCPServer (unsigned int *conversationHandle,
unsigned int portNumber,
char serverHostName[],
tcpFuncPtr clientCallbackFunction,
void *callbackData, unsigned int timeout);
Purpose
Establishes a conversation between your program and a pre-existing server. Your program
becomes a client.
Parameters
Input

portNumber

unsigned integer

Uniquely identifies a server on
a single machine.

serverHostName

character array

Can either be the host name or
IP address string.
For example, aaa.bbb.ccc
or 123.456.78.90.

Output

clientCallbackFunction

TCP function
pointer

Pointer to the user callback
function.

callbackData

void pointer

User-defined data.

timeout

unsigned integer

Timeout in ms.

conversationHandle

unsigned integer

Uniquely identifies the
conversation.

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Return Value
status

integer

Refer to error codes in
Table 7-3.

Parameter Discussion
clientCallbackFunction is the name of the function called to process messages to your program
as a TCP client.
The callback function must be of the following form:
int (*tcpFuncPtr) (int handle, int xType, int errCode, void *callbackData);

The xType (transaction type) parameter specifies the type of message received from the server.
The client callback function can receive the following transaction types.
TCP_DISCONNECT
TCP_DATAREADY

The errCode parameter is used only when the transaction type is TCP_DISCONNECT.
The following describes each transaction type.
TCP_DISCONNECT—Received when a server is requesting the termination of a connection, or
when a connection is being terminated due to an error. If the connection is terminated due to an
error, the errCode parameter contains a negative error code. Refer to Table 7-3 for the list of
error codes.
TCP_DATATREADY—Received when the server has sent data via TCP to the client. Your
program, acting as the client, should call ClientTCPRead to obtain the data.
The client callback function should return TRUE if the message can be processed successfully.
Otherwise, the function should return FALSE.
Note: The callback function should be short and should return as soon as possible.
callbackData is a four-byte value that will be passed to the callback function each time it is
called for this client.
You should define the meaning of the callback data. One way to use the callbackData is as a
pointer to a data object that you need to access in the callback function. In this way, you would
not need to declare the data object as a global variable.
If you do not want to use the callbackData, you can pass zero.

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See Also
RegisterTCPServer, DisconnectFromTCPServer

DisconnectFromTCPServer
int status = DisconnectFromTCPServer (unsigned int conversationHandle);
Purpose
Disconnects your client program from a server application.
Parameters
Input

conversationHandle unsigned integer Uniquely identifies the conversation.

Return Value
integer

status

Refer to error codes in Table 7-3.

Note: This function terminates a connection identified by the conversation handle passed.
There can be more than one conversation between a client and a server.
See Also
ConnectToTCPServer, RegisterTCPServer

DisconnectTCPClient
int status = DisconnectTCPClient (unsigned int conversationHandle);
Purpose
Called by a TCP server to terminate a connection with a client. (Be aware that there can be more
than one conversation between a server and a client.)
Parameters
Input

conversationHandle

unsigned integer

Uniquely identifies the connection.

integer

Refer to error codes in Table 7-3.

Return Value
status

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See Also
RegisterTCPServer

GetTCPErrorString
char *message = GetTCPErrorString (int errorNum)
Purpose
Converts the error number returned by a TCP Library function into a meaningful error message.
Parameters
Input

errorNum

integer

Status returned by a TCP function.

string

Explanation of error.

Return Value
message

RegisterTCPServer
int status = RegisterTCPServer (unsigned int portNumber,
tcpFuncPtr serverCallbackFunction,
void *callbackData);
Purpose
Registers your program as a valid TCP server and allows other applications to connect to it for
network communication.
Parameters
Input

portNumber

unsigned integer

serverCallbackFunction TCP function
pointer
callbackData

LabWindows/CVI Standard Libraries

void pointer

7-8

Uniquely identifies a server on
a single machine.
Pointer to the user callback
function.
Pointer to the user data.

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Return Value
status

integer

Refer to error codes in
Table 7-3.

Parameter Discussion
serverCallbackFunction is the name of the function to be called to process client requests.
The callback function must be of the following form:
int (*tcpFuncPtr) (int handle, int xType, int errCode,
void *callbackData)
The xType parameter specifies the type of message received from the server. The server
callback function can receive the following transaction types.
TCP_CONNECT
TCP_DISCONNECT
TCP_DATAREADY

The errCode parameter is used only when the transaction type is TCP_DISCONNECT.
The following describes each transaction type.
TCP_CONNECT—The transaction type is received when a client is requesting a connection.
TCP_DISCONNECT—Received when a client is requesting the termination of a connection, or
when a connection is being terminated due to an error. If the connection is terminated due to an
error, the errCode parameter contains a negative error code. Refer to Table 7-3 for the list of
error codes.
TCP_DATATREADY—Received when the client has sent data via TCP to the server. Your
program, acting as the server, should call ServerTCPRead to obtain the data.
The server callback function should return TRUE if the request is successful. Otherwise, the
function should return FALSE.
Note: Server callback should be short and should return as soon as possible.
callbackData is a four-byte value that will be passed to the callback function each time it is
called for this server.

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It is up to you to define the meaning of the callback data. The following are examples of how the
callback data can be used:
•

You can register your program as a TCP server multiple times under different port numbers.
You could use the same callback function for all of the server instances by using the callback
data to differentiate between them.

•

You can use the callback data to point to a data object that you need to access in the callback
function. In this way, you would not need to declare the data object as a global variable.

If you do not want to use the callback data, you can pass zero.
See Also
ConnectToTCPServer, UnregisterTCPServer

ServerTCPRead
int status = ServerTCPRead (unsigned int conversationHandle, void *dataBuffer,
unsigned int dataSize, unsigned int timeout);
Purpose
Reads data from a TCP client application.
Parameters
Input

conversationHandle

unsigned integer

Uniquely identifies the
conversation.

dataBuffer

void pointer

Buffer in which to receive data.

dataSize

unsigned integer

Number of bytes to read.

timeout

unsigned integer

Timeout in ms.

integer

Returns the number of bytes
written, or a negative error code
if an error occurs; Refer to error
codes in Table 7-3.

Return Value
status

See Also
RegisterTCPServer, ServerTCPWrite

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ServerTCPWrite
int status = ServerTCPWrite (unsigned int conversationHandle, void *dataPointer,
unsigned int dataSize, unsigned int timeout);
Purpose
Writes data to a TCP client application.
Parameters
Input

conversationHandle unsigned integer

Uniquely identifies the conversation.

dataPointer

void pointer

Buffer holding data.

dataSize

unsigned integer

Number of bytes to write.

timeout

unsigned integer

Timeout in ms.

integer

Returns the number of bytes written, or a
negative error code if an error occurs; Refer
to error codes in Table 7-3.

Return Value
status

See Also
RegisterTCPServer, ServerTCPRead

UnregisterTCPServer
int status = UnregisterTCPServer (unsigned int portNumber);
Purpose
Unregisters your server application program as a TCP server.
Parameters
Input

portNumber

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Return Value
integer

status

Refer to error codes in Table 7-3.

See Also
RegisterTCPServer

Error Conditions
If an error condition occurs during a call to any of the functions in the LabWindows/CVI TCP
Library, the status return value contains the error code. This code is a non-zero value that
specifies the type of error that occurred. Error code return values are negative numbers. The
currently defined error codes and their associated meanings are shown in Table 7-3.
Table 7-3. TCP Library Error Codes
Code
0

Error Message
kTCP_NoError

-1

-kTCP_UnableToRegisterService

-2

-kTCP_UnableToEstablishConnection

-3

-kTCP_ExistingServer

-4

-kTCP_FailedToConnect

-5

-kTCP_ServerNotRegistered

-6

-kTCP_TooManyConnections

-7

-kTCP_ReadFailed

-8

-kTCP_WriteFailed

-9

-kTCP_InvalidParameter

-10

-kTCP_OutOfMemory

-11

-kTCP_TimeOutErr

-12

-kTCP_NoConnectionEstablished

-13

-kTCP_GeneralIOErr

-14

-kTCP_ConnectionClosed

-15

-kTCP_UnableToLoadWinsockDLL

-16

-kTCP_IncorrectWinsockDLLVersion

-17

-kTCP_NetworkSubsystemNotReady

-18

-kTCP_ConnectionsStillOpen

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Utility Library
This chapter describes the functions in the LabWindows/CVI Utility Library. The Utility
Library contains functions that do not fit into any of the other LabWindows/CVI libraries. The
Utility Library Function Panels section contains general information about the Utility Library
functions and panels. The Utility Library Function Reference section contains an alphabetical
list of function descriptions.

The Utility Library Function Panels
The Utility Library function panels are grouped in a tree structure according to the type of
operations they perform.
The Utility Library function tree is shown in Table 8-1.
The bold headings in the tree are the names of function classes. Function classes are groups of
related function panels. The headings in plain text are the names of the individual function
panels. The names of the Utility Library functions appear in bold italics beneath the
corresponding function panel names.
Table 8-1. The Utility Library Function Tree
Timer/Wait
Timer
Delay
Synchronized Wait
Date/Time
Date in ASCII Format
Time in ASCII Format
Get System Date
Set System Date
Get System Time
Set System Time
Keyboard
Key Hit?
Get a Keystroke

Timer
Delay
SyncWait
DateStr
TimeStr
GetSystemDate
SetSystemDate
GetSystemTime
SetSystemTime
KeyHit
GetKey
(continues)

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Table 8-1. The Utility Library Function Tree (Continued)
File Utilities
Delete File
Rename File
Copy File
Get File Size
Get File Date
Set File Date
Get File Time
Set File Time
Get File Attributes
Set File Attributes
Get First File
Get Next File
Make Pathname
Split Path
Directory Utilities
Get Directory
Get Project Directory
Get Module Directory
Get Full Path From Project
Set Directory
Make Directory
Delete Directory
Get Drive
Set Drive
External Modules
Load External Module
Load External Module Ex
Run External Module
Get External Module Address
Unload External Module
Release External Module
Port I/O
Input Byte From Port
Input Word From Port
Output Byte To Port
Output Word To Port

DeleteFile
RenameFile
CopyFile
GetFileSize
GetFileDate
SetFileDate
GetFileTime
SetFileTime
GetFileAttrs
SetFileAttrs
GetFirstFile
GetNextFile
MakePathname
SplitPath
GetDir
GetProjectDir
GetModuleDir
GetFullPathFromProject
SetDir
MakeDir
DeleteDir
GetDrive
SetDrive
LoadExternalModule
LoadExternalModuleEx
RunExternalModule
GetExternalModuleAddr
UnloadExternalModule
ReleaseExternalModule
inp
inpw
outp
outpw
(continues)

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Table 8-1. The Utility Library Function Tree (Continued)
Standard Input/Output Window
Clear Screen
Get Stdio Window Options
Set Stdio Window Options
Get Stdio Window Position
Set Stdio Window Position
Get Stdio Window Size
Set Stdio Window Size
Get Stdio Window Visibility
Set Stdio Window Visibility
Get Stdio Port
Set Stdio Port
Run-Time Error Reporting
Set Break On Library Errors
Get Break On Library Errors
Set Break On Protection Errors
Get Break On Protection Errors
Old-Style Functions
Enable Break On Library Errors
Disable Break On Library Errors
Interrupts
Disable Interrupts
Enable Interrupts
Get Interrupt State
Physical Memory Access
Read From Physical Memory
Read From Physical Memory Ex
Write To Physical Memory
Write To Physical Memory Ex
Persistent Variable
Set Persistent Variable
Get Persistent Variable
Task Switching
Disable Task Switching
Enable Task Switching

Cls
GetStdioWindowOptions
SetStdioWindowOptions
GetStdioWindowPosition
SetStdioWindowPosition
GetStdioWindowSize
SetStdioWindowSize
GetStdioWindowVisibility
SetStdioWindowVisibility
GetStdioPort
SetStdioPort
SetBreakOnLibraryErrors
GetBreakOnLibraryErrors
SetBreakOnProtectionErrors
GetBreakOnProtectionErrors
DisableBreakOnLibraryErrors
EnableBreakOnLibraryErrors
DisableInterrupts
EnableInterrupts
GetInterruptState
ReadFromPhysicalMemory
ReadFromPhysicalMemoryEx
WriteToPhysicalMemory
WriteToPhysicalMemoryEx
SetPersistentVariable
GetPersistentVariable
DisableTaskSwitching
EnableTaskSwitching
(continues)

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Table 8-1. The Utility Library Function Tree (Continued)
Launching Executables
Launch Executable
Extended Functions
Launch Executable Extended
Has Executable Terminated?
Terminate Executable
Retire Executable Handle
Miscellaneous
System Help
Get CVI Version
Get Current Platform
In Standalone Executable?
Initialize CVI Run-Time Engine
Close CVI Run-Time Engine
Low-Level Support Driver Loaded
Beep
Breakpoint
Round Real To Nearest Integer
Truncate Real Number
Get Window Display Setting

LaunchExecutable
LaunchExecutableEx
ExecutableHasTerminated
TerminateExecutable
RetireExecutableHandle
SystemHelp
GetCVIVersion
GetCurrentPlatform
InStandaloneExecutable
InitCVIRTE
CloseCVIRTE
CVILowLevelSupportDriverLoaded
Beep
Breakpoint
RoundRealToNearestInteger
TruncateRealNumber
GetWindowDisplaySetting

The classes in the function tree are described here:
•

Timer/Wait functions use the system timer, including functions that wait on a timed basis.

•

Date/Time functions return the date or time in ASCII or integer formats, and set the date or
time.

•

Keyboard functions provide access to user keystrokes.

•

File Utilities functions manipulate files.

•

Directory Utilities functions manipulate directories and disk drives.

•

External Modules functions load, execute, and unload files that contain compiled C object
modules.

•

Port I/O functions read and write data from I/O ports (Supported only under Microsoft
Windows).

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•

Standard Input/Output Window functions control various attributes of the Standard
Input/Output Window.

•

Run-Time Error Reporting functions enable and disable the feature which breaks execution
when a LabWindows/CVI library function returns an error code.

•

Interrupts functions disable and enable the occurrence of interrupts.

•

Physical Memory Access functions read and write data from and to physical memory
addresses. (Supported only under Microsoft Windows).

•

Persistent Variable functions store and retrieve an integer value across multiple builds and
executions of a project in the LabWindows/CVI development environment.

•

Task Switching functions control whether a user can switch to another task under Microsoft
Windows.

•

Launching Executables functions start another executable, check whether it is still running,
and terminate it.

•

Miscellaneous functions perform a variety of operations that do not fit into any of the other
function classes.

The online help with each panel contains specific information about operating each function
panel.

Utility Library Function Reference
This section describes the functions in the LabWindows/CVI Utility Library. The
LabWindows/CVI Utility Library functions are arranged alphabetically.

Beep
void Beep (void);
Purpose
Sounds the speaker.
Parameters
None
Return Value
None

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Breakpoint
void Breakpoint (void);
Purpose
During execution of a program, a call to Breakpoint suspends program operation. While the
program is suspended, you can inspect or modify variables, and use many other features of the
LabWindows/CVI interactive program.
Calling Breakpoint with the debugging level set to None, or from a compiled module, has no
effect.
Parameters
None
Return Value
None

CloseCVIRTE
void CloseCVIRTE (void)
Purpose
This function releases memory in the LabWindows/CVI Run-Time Engine that was allocated by
InitCVIRTE for a particular DLL.
If you call InitCVIRTE from DllMain, you also should call CloseCVIRTE from
DllMain. You should call it in response to the DLL_PROCESS_DETACH message after your
other detach code.
Parameters
None
Return Value
None

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Cls
void Cls (void);
Purpose
In the LabWindows/CVI environment, this function clears the Standard I/O window.
Parameters
None
Return Value
None

CopyFile
int result = CopyFile (char sourceFileName[], char targetFileName[]);
Purpose
Copies the contents of an existing file to another file.
Parameters
Input

sourceFileName

string

File to copy.

targetFileName

string

Copy of original file.

integer

Result of copy operation.

Return Value
result
Return Codes
0

Success.

-1

File not found or directory in path not found.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-5

Invalid path (for either of the file names).

-6

Access denied.

-7

Specified path is a directory, not a file.

-8

Disk is full.

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Parameter Discussion
sourceFileName and targetFileName may contain wildcard characters ‘?’ and ‘*’. If
sourceFileName has wildcards, all matching files are copied. If targetFileName has wildcards,
it will be matched to sourceFileName. If the target file is a directory, the existing file (or group
of files) will be copied into the directory.
sourceFileName may also be the empty string (""), in which case the file found by the most
recent call to GetFirstFile or GetNextFile is copied.

CVILowLevelSupportDriverLoaded
int loaded = CVILowLevelSupportDriverLoaded (void);
Note: This function is available only in the Windows 95 and NT version of
LabWindows/CVI.
Purpose
This function returns an indication of whether the LabWindows/CVI low-level support driver
was loaded at startup. The following Utility Library functions require the LabWindows/CVI lowlevel driver to be loaded at startup.

Function
inp

Platforms where low-level
support driver is needed
Windows NT

inpw

Windows NT

outp

Windows NT

outpw

Windows NT

ReadFromPhysicalMemory

Windows 95 and NT

ReadFromPhysicalMemoryEx Windows 95 and NT
WriteToPhysicalMemory
Windows 95 and NT
WriteToPhysicalMemoryEx

Windows 95 and NT

DisableInterrupts

Windows 95

EnableInterrupts

Windows 95

DisableTaskSwitching

Windows 95

Most of these functions do not return an error if the low-level support driver is not loaded. To
make sure your calls to these functions can execute correctly, call
CVILowLevelSupportDriverLoaded at the beginning of your program.

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Return Value
loaded

integer

Indicates whether the LabWindows/CVI low-level
support driver was loaded at startup.

Return Codes
1

Low-level support driver was loaded at startup.

0

Low-level support driver was not loaded at startup.

DateStr
char *s = DateStr (void);
Purpose
Returns a 10-character string in the form MM-DD-YYYY, where MM is the month, DD is the day,
and YYYY is the year.
Parameters
None
Return Value
10-character string

s

The date in MM-DD-YYYY
format.

Delay
void Delay (double numberofSeconds);
Purpose
Waits the number of seconds indicated by numberofSeconds. The resolution on Windows is
normally 1 millisecond. However, if the following line appears in the CVI section of your
WIN.INI file, the resolution is 55 milliseconds.
useDefaultTimer = True
The resolution on Sun Solaris is 1 millisecond.

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Parameter
Input

numberofSeconds

double-precision

Number of seconds to wait.

Return Value
None

DeleteDir
int result = DeleteDir (char directoryName[]);
Purpose
Deletes an existing directory.
Parameters
Input

directoryName

String.

Return Value
integer

result

Result of operation.

Return Codes
0

Success.

-1

Directory not found.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-6

Access denied, or directory not empty.

-7

Path is a file, not a directory.

DeleteFile
int result = DeleteFile (char fileName[]);
Purpose
Deletes an existing file from disk.

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Parameter
Input

fileName

string

File to delete.

integer

Result of delete operation.

Return Value
result
Return Codes
0

Success.

-1

File not found or directory in path not found.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-5

Invalid path (for example, c:filename in Windows).

-6

Access denied.

-7

Specified path is a directory, not a file.

Parameter Discussion
fileName may contain wildcard characters ‘?’ and ‘*’ in which case all matching files are
deleted.
fileName may also be the empty string ("") in which case the file found by the most recent call
to GetFirstFile or GetNextFile is deleted.

DisableBreakOnLibraryErrors
void DisableBreakOnLibraryErrors (void);
Purpose
If debugging is enabled (if the debugging level in the Run Options dialog box of the Options
menu in the Project window is set to Standard or Extended), this function directs
LabWindows/CVI not to display a run-time error dialog box when a National Instruments library
function reports an error. If debugging is disabled, this function has no effect.

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You can use this function in conjunction with EnableBreakOnLibraryErrors to
temporarily suppress the Break on Library Errors feature around a segment of code. It does not
affect the state of the Break on Library Errors check box in the Run Options dialog box of the
Options menu in the Project window.
Note: This function has been superseded by SetBreakOnLibraryErrors.

DisableInterrupts
void DisableInterrupts (void);
Purpose
Under Windows 3.1 and Windows 95, this function uses the CLI instruction to turn off all
maskable 80x86 interrupts. On UNIX, this function uses sigblock to block all blockable
signals.
Note: For you to be able to use this function under Windows 95, the LabWindows/CVI lowlevel support driver must be loaded.
Note: Under Windows NT, the EnableInterrupts and DisableInterrupts
functions have no effect. Interrupts are always enabled while your program is running
at the user (as opposed to the kernel) level.
Parameter
None
Return Value
None

DisableTaskSwitching
void DisableTaskSwitching (void);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
This function prevents the end-user from using one of the following Windows features to switch
another task.

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•

The , , or  key combination under Windows 3.1 or Windows 95.

•

The Switch To item in the system menu under Windows 3.1.

This function affects the behavior of these keys only while LabWindows/CVI or a
LabWindows/CVI Standalone Executable is the active application under Microsoft Windows.
This function has no effect in Windows NT. See the Alternatives in Windows NT section for
instructions on how to achieve the desired effect.
Note: To use this function on Windows 95, the LabWindows/CVI low-level support driver
must be loaded.
Disabling the Task List
DisableTaskSwitching does not prevent the user from clicking on the desktop to get the
task list in Windows 3.1, or clicking on the task bar in Windows 95. You can prevent the user
from clicking on the desktop by forcing your window to cover the entire screen.
Forcing Window to Cover Entire Screen
You can force your window to cover the entire screen by making the following calls to functions
in the User Interface Library.
SetPanelAttribute
SetPanelAttribute
SetPanelAttribute
SetPanelAttribute
SetPanelAttribute
SetPanelAttribute

(panel,
(panel,
(panel,
(panel,
(panel,
(panel,

ATTR_SIZABLE, FALSE);
ATTR_CAN_MINIMIZE, FALSE);
ATTR_CAN_MAXIMIZE, FALSE);
ATTR_SYSTEM_MENU_VISIBLE, FALSE);
ATTR_MOVABLE, FALSE);
ATTR_WINDOW_ZOOM, VAL_MAXIMIZE);

In these calls, panel is the panel handle for your top-level window. These calls will work in
Windows 3.1, Windows 95, and Windows NT.
Alternatives in Windows 3.1
Under Windows 3.1, you can prevent the end-user accessing the task list by disabling the Task
Manager. Change a line in your system.ini [boot] section from
taskman.exe = taskman.exe

to
taskman.exe =

Forcing your window to cover the entire screen or disabling the Task Manager does not prevent
the user from task switching using the  and  key combinations. You must
also call DisableTaskSwitching to disable the  and  key
combinations. As an alternative to calling DisableTaskSwitching, you can arrange for

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your standalone application to be brought up in place of the Program Manager when Windows
boots. You can do this by changing the following line in your system.ini [boot] section.
shell = progman.exe

to
shell = 

Alternatives in Windows 95
Under Windows 95, you can arrange for your standalone application to appear in place of the
desktop when Windows boots.
You can do this by changing the following line in your system.ini [boot] section.
shell = Explorer.exe

to
shell = 

Alternatives in Windows NT
Under Windows NT, you can achieve the same results as DisableTaskSwitching by
arranging for your LabWindows/CVI application to be brought up in place of the Program
Manager and by disabling the Task Manager. You can do this by making following changes to
the registry entry for the key name,
KEY_LOCAL_MACHINE\Software\Microsoft\CurrentVersion\Winlogon

•

Change the value for SHELL to the pathname of your application executable.

•

Add a value with the name TASKMAN. Set the data to an empty string.

Preventing Interference With Real-Time Processing
Under Windows, many user actions can interfere with real-time processing. The actions in the
following list suspend the processing of events.
•

Moving and sizing top-level windows

•

Bringing down the System menu

•

Pressing the  key combination

You can prevent these user actions from interfering with event processing by doing all of the
following.
•

Call DisableTaskSwitching (or use the alternative for Windows NT mentioned in this
section).

•

Make all of your top-level panels non-movable and non-sizable.

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•

Do not use the Standard I/O Window in your final application.

•

If you use any of the built-in pop-ups in the User Interface Library, make the following calls.
SetSystemPopupsAttribute (ATTR_MOVABLE, 0);
SetSystemPopupsAttribute (ATTR_SYSTEM_MENU_VISIBLE, 0);

An alternative approach is available on Windows 95 and NT. You can enable timer control
callbacks while  is pressed, while the system menu is pulled down, or (in some cases)
while a window is being moved or sized. You can do this by using the following function call.
SetSystemAttribute (ATTR_ALLOW_UNSAFE_TIMER_EVENTS, 1);

This alternative is incomplete and can be unsafe. See the discussion on Unsafe Timer Events in
the Using the System Attributes section of Chapter 3, Programming with the User Interface
Library, of the LabWindows/CVI User Interface Reference Manual.

EnableBreakOnLibraryErrors
void EnableBreakOnLibraryErrors (void);
Purpose
If debugging is enabled (if the debugging level in the Run Options dialog box of the Options
menu in the Project window is set to Standard or Extended), this function directs
LabWindows/CVI to display a run-time error dialog box when a National Instruments library
function reports an error. If debugging is disabled, this function has no effect.
In general, you should check the Break on Library Errors check box in the Run Options dialog
box of the Options menu in the Project window to enable this feature. However, you can use this
function in conjunction with DisableBreakOnLibraryErrors to temporarily suppress the
Break on Library Errors feature around a segment of code. It does not affect the state of the
Break on Library Errors check box.
Note: This function has been superseded by SetBreakOnLibraryErrors.

EnableInterrupts
void EnableInterrupts (void);
Under Windows 3.1 and Windows 95, this function uses the STI instruction to turn on all
maskable 80x86 interrupts. On UNIX, this function reverses the effect of the last call to
DisableInterrupts. It restores the signal processing state to the condition prior to the
DisableInterrupts call.

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Note: For you to be able to use this function under Windows 95, the LabWindows/CVI lowlevel support driver must be loaded.
Note: Under Windows NT, the EnableInterrupts and DisableInterrupts
functions have no effect. Interrupts are always enabled while your program is running
at the user (as opposed to the kernel) level.
Parameter
None
Return Value
None

EnableTaskSwitching
void EnableTaskSwitching (void);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
This function lets the user switch to another task by using the , , and
 key combinations, as well as the Switch-To item in the Control/System menu. This
function only affects the behavior of these keys while LabWindows/CVI or a LabWindows/CVI
standalone executable is the active application.

ExecutableHasTerminated
int status = ExecutableHasTerminated (int executableHandle);
Purpose
Determines whether an application started with LaunchExecutableEx has terminated.
Parameters
Input executableHandle

LabWindows/CVI Standard Libraries

integer The executable handle acquired from
LaunchExecutableEx.

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Return Value
integer Result of operation.

status
Return Codes
-1

Handle is invalid.

0

Executable is still running.

1

Executable has been terminated.

Note: If you launch another LabWindows/CVI executable under Windows 3.x, the launched
executable process will terminate itself after launching the new copy of the
CVI Run-time Engine. If you use ExecutableHasTerminated, the return value
will always be 1 because the process identification for the second Run-time Engine
cannot be tracked. See LaunchExecutableEx for more information.

GetBreakOnLibraryErrors
int state = GetBreakOnLibraryErrors (void);
Purpose
This function returns the state of the Break on library errors option. It returns a 1 if the Break
on library errors option is enabled, or a 0 if it is disabled.
The state of the Break on Library errors option can be changed interactively using the Run
Options command in the Options menu of the Project window. The state of the Break on
Library errors option can also be changed programmatically using
SetBreakOnLibraryErrors, or the EnableBreakOnLibraryErrors and
DisableBreakOnLibraryErrors functions.
If debugging is disabled, this function always returns 0.
Return Value
state

integer

The current state of the Break on library errors option.

Return Codes
1

Break on Library Errors option enabled.

0

Break on Library Errors option disabled.

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GetBreakOnProtectionErrors
int state = GetBreakOnProtectionErrors (void);
Purpose
This function returns the state of the break on protection errors feature. It returns a 1 if the
option is enabled, or a 0 if it is disabled. If debugging is disabled, this function always returns 0.
For more information on the feature, see the documentation for
SetBreakOnProtectionErrors.
Return Value
state

integer

The current state of the break on protection errors option.

Return Codes
1

Break on protection errors option enabled.

0

Break on protection errors option disabled.

GetCVIVersion
int versionNum = GetCVIVersion (void);
Purpose
This function returns the version of LabWindows/CVI you are running. In a standalone
executable, this tells you which version of the LabWindows/CVI run-time libraries you are
using.
The value is in the form Nnn, where the N.nn is the version number that shows in the About
LabWindows/CVI dialog box.
For example, for LabWindows/CVI version 4.0, GetCVIVersion returns 400. For version 4.1,
it would return 410. The values will always increase with each new version of
LabWindows/CVI.
The return value of GetCVIVersion should not be confused with the predefined macro
_CVI_, which specifies the version of LabWindows/CVI in which the source file is compiled.
Return Value
versionNum

integer

LabWindows/CVI Standard Libraries

The version number of LabWindows/CVI or the runtime libraries.

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Return Codes
Nnn

Where N.nn is the LabWindows/CVI version.

GetCurrentPlatform
int platformCode = GetCurrentPlatform (void);
Purpose
This function returns a code representing the operating system under which a project or
standalone executable is running.
The return value of GetCurrentPlatform should not be confused with the predefined
macros such as _NI_mswin_, _NI_unix_, and others, which specify the platform on which
the project is compiled.
This function is useful when you have a program that can run on multiple operating systems but
must take different actions on the different systems. For example, the same standalone
executable can run on both Windows 95 and Windows NT. If the program needs to behave
differently on the two platforms, you can use GetCurrentPlatform to determine the
platform at run-time.
Return Value
platformCode

integer

Indicates the current operating system.

Return Codes
kPlatformWin16

1

Windows 3.1

kPlatformWin95

2

Windows 95

kPlatformWinnt

3

Windows NT

kPlatformSunos4

4

Sun Solaris 1

kPlatformSunos5

5

Sun Solaris 2

kPlatformHPUX9

6

HP-UX 9.x

kPlatformHPUX10

7

HP-UX 10.x

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GetDir
int result = GetDir (char currentDirectory[]);
Purpose
Gets the current working directory on the default drive.
Parameter
Output

currentDirectory

string

Current directory.

integer

Result of operation.

Return Value
result
Return Codes
0

Success.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

Parameter Discussion
currentDirectory must be at least MAX_PATHNAME_LEN bytes long.

GetDrive
int result = GetDrive (int *currentDriveNumber, int *numberofDrives);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
Gets the current default drive number and the total number of logical drives in the system.
Parameters
Output

currentDriveNumber

integer

Current default drive number.

numberofDrives

integer

Number of logical drives.

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Return Value
integer

result

Result of operation.

Return Codes
0

Success.

-1

Current directory is on a network drive that is not mapped to a local drive.
(currentDriveNumber is set correctly, but numberOfDrives is set to -1.)

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-6

Access denied.

Parameter Discussion
The mapping between the drive number and the logical drive letter is 0 = A, 1 = B, and so on.
The total number of logical drives includes floppy-disk drives, hard-disk drives, RAM disks, and
networked drives.

GetExternalModuleAddr
void *address = GetExternalModuleAddr (char name[], int moduleID, int *status);
Purpose
Obtains the address of an identifier in a module that was loaded using
LoadExternalModule.
Parameters
Input

name
moduleID

string
integer

Name of identifier.
ID of loaded module.

Output

status

integer

Zero or error code.

void pointer

Address of the identifier.

Return Value
address

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Return Codes
0

Success.

-1

Out of memory.

-4

Invalid file format.

-5

Undefined references.

-8

Cannot open file.

-9

Invalid module ID.

-10

Identifier not defined globally in module.

-25

DLL initialization failed (e.g. DLL file not found).

Parameter Discussion
moduleID is the value LoadExternalModule returns.
name is the name of the identifier whose address is obtained from the external module. The
identifier must be a variable or function name defined globally in the external module.
status is zero if the function is a success, or a negative error code if it fails.
If GetExternalModuleAddr succeeds, it returns the address of the variable or function in
the module. If the function fails, it returns NULL.
Example
void (*funcPtr) (char buf[], double dval, int *ival);
int module_id;
int status;
char buf[100];
double dval;
int ival;
char *pathname;
char *funcname;
pathname = "EXTMOD.OBJ";
funcname = "my_function";
module_id = LoadExternalModule (pathname);
if (module_id < 0)
FmtOut ("Unable to load %s\n", pathname);
else
{
funcPtr = GetExternalModuleAddr (module_id, funcname, &status);
if (funcPtr == NULL)
FmtOut ("Could not get address of %s\n", funcname);
else
(*funcPtr) (buf, dval, &ival);
}

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GetFileAttrs
int result = GetFileAttrs (char fileName[], int *read-only, int *system, int *hidden,
int *archive);
Note: Only available on the Windows version of LabWindows/CVI.
Purpose
Gets the following attributes of a file:
•

Read-Only

•

System

•

Hidden

•

Archive

The read-only attribute makes it impossible to write to the file or create a file with the same
name.
The system attribute and hidden attribute both prevent the file from appearing in a directory list
and exclude it from normal searches.
The archive attribute is set whenever you modify the file, and cleared by the DOS BACKUP
command.
Parameters
Input

fileName

string

File to get attributes.

Output

read-only

integer

Read only attribute.

system

integer

System attribute.

hidden

integer

Hidden attribute.

archive

integer

Archive attribute.

integer

Result of operation.

Return Value
result
Return Codes
0

Success.

1

Specified file is a directory.

-1

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Parameter Discussion
Each attribute parameter will contain one of the following values:
0—attribute is not set
1—attribute is set
fileName may be the empty string (""), in which case the attributes of the file found by the most
recent call to GetFirstFile or GetNextFile are returned.
Example
/* get the attributes of WAVEFORM.DAT */
int read_only,system,hidden,archive;
GetFileAttrs ("waveform.dat",&read_only,&system,&hidden,&archive);
if (read_only)
FmtOut("WAVEFORM.DAT is a read-only file!");

GetFileDate
int result = GetFileDate (char fileName[], int *month, int *day, int *year);
Purpose
Gets the date of a file.
Parameters
Input

fileName

string

File to get date.

Output

month

integer

Month (1 to 12).

day

integer

Day of month (1 to 31).

year

integer

Year (1980–2099).

integer

Result of operation.

Return Value
result

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Return Codes
0

Success.

-1

File not found or directory in path not found.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-5

Invalid path (for example, c:filename in Windows).

-6

Access denied.

Parameter Discussion
fileName may be the empty string (""), in which case the date of the file found by the most
recent call to GetFirstFile or GetNextFile is returned (Windows only).
Example
/* get the date of WAVEFORM.DAT */
int month, day, year;
GetFileDate ("waveform.dat",&month,&day,&year);

GetFileSize
int result = GetFileSize (char fileName[], long *fileSize);
Purpose
Returns the size of a file.
Parameters
Input

fileName

string

Name of file.

Output

fileSize

long

Size of file in bytes.

integer

Result of operation.

Return Value
result

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Return Codes
0

Success.

-1

File not found or directory in path not found.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-5

Invalid path (for example, c:filename in Windows).

-6

Access denied.

Parameter Discussion
fileName may be the empty string (""), in which case the size of the file found by the most
recent call to GetFirstFile or GetNextFile is returned (Windows only).
Example
long size;
if (GetFileSize ("waveform.dat",&size) == 0)
FmtOut("The size of WAVEFORM.DAT is %i[b4]",size);

GetFileTime
int result = GetFileTime (char fileName[], int *hours, int *minutes, int *seconds);
Purpose
Gets the time of a file.
Parameters
Input

fileName

string

File to get date.

Output

hours

integer

Hours (0 to 23).

minutes

integer

Minutes (0 to 59).

seconds

integer

Number of 2-second increments
(0-29).

integer

Result of operation.

Return Value
result

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Return Codes
0

Success.

-1

File not found or directory in path not found.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-5

Invalid path (for example, c:filename in Windows).

-6

Access denied.

Parameter Discussion
fileName may be the empty string (""), in which case the time of the file found by the most
recent call to GetFirstFile or GetNextFile is returned (Windows only).
Example
/* get the time of WAVEFORM.DAT */
int hours,minutes,seconds;
GetFileTime ("waveform.dat",&hours,&minutes,&seconds);

GetFirstFile
int result = GetFirstFile (char searchPath[], int normal, int read-only, int system,
int hidden, int archive, int directory, char fileName[]);
Purpose
Starts a search for files with specified attributes and returns the first matching file. If you select
multiple attributes, a match occurs on the first file for which one or more of the specified
attributes are set and which matches the pattern in the searchPath parameter. The search
attributes are:
•

Normal

•

Read-only

•

System

•

Hidden

•

Archive

•

Directory

Under UNIX, only the directory attribute is honored. If you pass 1 for the directory attribute,
only directories match. If you pass 0 for the directory attribute, only non-directories match.

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Under Windows, all of the attributes are honored. The normal attribute specifies files with no
other attributes set or with only the archive bit set. The archive attribute specifies files that have
been modified because they were last backed up using the DOS BACKUP command. The readonly attribute specifies files that are protected from being modified or overwritten. The system
and hidden attributes specify files which normally do not appear in a directory listing. The
directory attribute specifies directories.
If you pass 1 only for the normal attribute, any file that is not read-only, not a system file, not
hidden, and not a directory can match. A normal file’s archive bit may be either on or off. The
normal attribute is the only attribute that requires other attributes not to be set. For example, if
you use the read-only attribute, any read-only file can match regardless of its other attributes.
This holds true for the system, hidden, directory, and archive attributes.
If you use more than one attribute, the effect is additive. For example, if you use the read-only
and directory attributes, all read-only files and all directories can match. If you use the normal
and read-only attributes, all normal files and all read-only files can match.
Parameters
Input

Output

searchPath

string

Path to search.

normal

integer

Normal attribute.

read-only

integer

Read-only attribute.

system

integer

System attribute.

hidden

integer

Hidden attribute.

archive

integer

Archive attribute.

directory

integer

Directory attribute.

fileName

string

First file found.

integer

Result of search.

Return Value
result
Return Codes
0

Success.

-1

No files found that match criteria.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-5

Invalid path (for example, c:filename in Windows).

-6

Access denied.

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Parameter Discussion
searchPath may contain the wildcard characters '*' and '?'.
Each attribute parameter can have one of the following values:
0— do not search for files with the attribute
1— search for files with the attribute
fileName contains the basename and extension of the first matching file and must be at least
MAX_FILENAME_LEN characters in length.

GetFullPathFromProject
int result = GetFullPathFromProject (char fileName[], char fullPathName[]);
Purpose
Gets the full pathname for the specified file, if the file is in the currently loaded project.
Parameters
Input

fileName

string

Name of file in project.

Output

fullPathName

string

Full pathname of file.

integer

Result of operation.

Return value
result
Return codes
0
-1

Success.
File was not found in project.

Parameter Discussion
fileName is the name of a file that is in the currently loaded project. The name must be a simple
file name and should not contain any directory paths. For example, file.c is a simple file
name, whereas dir\file.c is not.
fullPathName must be at least MAX_PATHNAME_LEN bytes long.

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Using This Function
This function is useful when your program needs to access a file in the project and you do not
know what directory the file is in.
Example
char *fileName;
char fullPath[MAX_PATHNAME_LEN];
fileName = "myfile.c"
if (GetFullPathFromProject (fileName, fullPath) < 0)
FmtOut ("File %s is not in the project\n", fileName);

Note: Runtime errors are not reported for this function.

GetInterruptState
int interruptstate = GetInterruptState (void);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
This function returns the state of the interrupt bit of the 80x86 CPU status flag.
On Windows NT, this function always returns 1. Interrupts are always enabled while your
program is running at the user (as opposed to the kernel) level.
Return Value
interrupt state

integer

Interrupt bit of 80x86 CPU
status flag.

GetKey
int k = GetKey (void);
Purpose
Waits for the user to press a key and returns the key code as an integer value.
Note: This function only detects keystrokes in the Standard I/O window. It does not detect
keystrokes in windows created with the User Interface Library or in the console
window in a Windows Console Application.

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Parameters
None
Return Value
integer

k

Key code.

Using This Function
The values returned are the same as the key values used in the User Interface Library. See
userint.h.
Keystroke

Return Value



'b'



(VAL_MENUKEY_MODIFIER | 'B')



VAL_F4_VKEY



(VAL_SHIFT_MODIFIER | VAL_F4_VKEY)

Note: This function returns -1 if you are running on UNIX and have done one of the
following.
•

Selected “Use hosts system’s standard Input/Output” in the dialog box brought up
by selecting Options » Environment in the Project window; or

•

Called SetStdioPort to set the port to HOST_SYSTEM_STDIO.

Example
/* Give the user a chance to quit the program */
int k;
FmtOut ("Enter 'q' to quit, any other key to continue ");
k = GetKey ();
if ((k == 0x0051) || (k == 0x0071))
/* q or Q */
exit (0);

GetModuleDir
int result = GetModuleDir (char directoryName[], void *moduleHandle);
Note: This function is available only in the Windows 95 and NT versions of
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Purpose
This function obtains the name of the directory of the specified DLL module.
This function is useful when a DLL and its related files are distributed to multiple users who may
place them in different directories. If your DLL needs to access a file that is in the same directory
as the DLL, you can use the GetModuleDir and MakePathname functions to construct the
full pathname.
If the specified module handle is zero, then this function returns the same result as
GetProjectDir.
Parameter List
Output directoryPathname

string

Directory of module.

Input

void
pointer

Module handle of DLL, or zero for the
project.

moduleHandle

Parameter Discussion
directoryPathname must be at least MAX_PATHNAME_LEN bytes long.
If you want to obtain the directory name of the DLL in which the call to GetModuleDir
resides, then pass __CVIUserHInst as the moduleHandle. You can pass any valid Windows
module handle. If you pass 0 for the moduleHandle, this function obtains the directory of the
project or standalone executable.
Return Value
integer

result

Result of the operation.

Return Codes
0

Success.

-1

The current project has no pathname (that is, it is untitled).

-2

There is no current project.

-3

Out of memory.

-4

The operating system is unable to determine the module directory (moduleHandle is
probably invalid).

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GetNextFile
int result = GetNextFile (char fileName[]);
Purpose
Gets the next file found in the search starting with GetFirstFile.
Parameters
Output

fileName

string

Next file found.

integer

Result of search.

Return Value
result
Return Codes
0

Success.

-1

No more files found matching criteria.

-2

GetFirstFile must initiate search.

Parameter Discussion
fileName will contain the basename and extension of the next matching file and must be at least
MAX_FILENAME_LEN characters in length.

GetPersistentVariable
void GetPersistentVariable (int *value);
Purpose
Returns the value set by SetPersistentVariable. However, if you unloaded the project
since you last called SetPersistentVariable, zero is returned.
In a standalone executable, zero is returned if you have not called SetPersistentVariable
since the start of execution.
Parameters
Output

value

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GetProjectDir
int result = GetProjectDir (char directoryName[]);
Purpose
Gets the name of the directory containing the currently loaded project file.
Parameters
Output

directoryName

string

Directory of project.

integer

Result of operation.

Return value
result
Return codes
0
-1

Success.
Current project has no pathname (it is untitled).

Parameter Discussion
directoryName must be at least MAX_PATHNAME_LEN bytes long.
Using This Function
This function is useful when a project and its related files are distributed to multiple users who
may place them in a different directory on each machine. If your program needs to access a file
that is in the same directory as the project, you can use GetProjectDir and
MakePathname to construct the full pathname.
Example
char *fileName;
char projectDir[MAX_PATHNAME_LEN];
char fullPath[MAX_PATHNAME_LEN];
fileName = "myfile";
if (GetProjectDir (projectDir) < 0)
FmtOut ("Project is untitled\n");
else
MakePathname (projectDir, fileName, fullPath);

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GetStdioPort
void GetStdioPort (int *stdioPort);
Purpose
Gets a value indicating the current destination for data written to the standard output (and the
source of data read from the standard input.)
The Standard I/O port can be either the CVI Standard Input/Output window or the standard
Input/Output of the host system.
This function is valid only on the UNIX version.
Parameters
Output

stdioPort

integer

0 = the CVI Standard
Input/Output window.
1 = the host system's standard
output.

GetStdioWindowOptions
void GetStdioWindowOptions (int *maxNumLines, int *bringToFrontWhenModified,
int *showLineNumbers);
Purpose
Gets the current value of the following Standard Input/Output window options:
Maximum Number of Lines
Bring To Front When Modified
Show Line Numbers

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Parameters
Output

maxNumLines

integer

bringToFrontWhenModified integer

showLineNumbers

integer

The maximum number of lines
that can be stored in the Standard
Input/Output window. If this
amount is exceeded, lines are
discarded from the top.
Indicates whether the Standard
Input/Output window is brought
to the front each time a string or
character is added to it.
1 = Yes.
0 = No.
Indicates whether line numbers
are shown in the Standard
Input/Output window.
1 = Yes.
0 = No.

Parameter Discussion
If you do not want to obtain any of these values, you can pass NULL.

GetStdioWindowPosition
void GetStdioWindowPosition (int *top, int *left);
Purpose
Gets the current position, in pixels, of the client area of the Standard Input/Output window
relative to the upper left corner of the screen. The client area begins under the title bar and to the
right of the frame.

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Parameters
Output

top

integer

The current distance, in pixels,
from the top of client area of the
Standard Input/Output window
to the top of the screen.

left

integer

The current distance, in pixels,
from the leftmost edge of client
area of the Standard
Input/Output window to the left
edge of the screen.

GetStdioWindowSize
void GetStdioWindowSize (int *height, int *width);
Purpose
Gets the height and width, in pixels, of the client area of the Standard Input/Output window. The
client area excludes the frame and the title bar.
Parameters
Output

height

integer

The current height, in pixels, of
the client area of the Standard
Input/Output window.

width

integer

The current width, in pixels, of
the client area of the Standard
Input/Output window.

GetStdioWindowVisibility
void GetStdioWindowVisibility (int *visible);
Purpose
Indicates whether the Standard Input/Output window is currently visible. If the window has been
made into an icon, it is considered to be not visible. If the window cannot be seen merely
because its position is off the screen it is considered to be visible.

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Parameters
Output

visible

integer

1 = Standard I/O window is
visible.
0 = Standard I/O window is not
visible.

GetSystemDate
int status = GetSystemDate (int *month, int *day, int *year);
Note: This function is only available on the Windows version of LabWindows/CVI.
Purpose
Obtains the system date in numeric format.
Parameters
Output

month

integer

Month (1–12).

day

integer

Day of month (1–31).

year

integer

Year (Under Windows 3.1, the
year is limited to the values
1980–2099).

integer

Success or failure.

Return Value
status
Return Codes
0
-1

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Success.
Failure reported by operating system.

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GetSystemTime
int status = GetSystemTime(int *hours, int *minutes, int *seconds);
Note: This function is only available on the Windows version of LabWindows/CVI.
Purpose
Obtains the system time in numeric format.
Parameters
Output

hours

integer

Hours (0–23).

minutes

integer

Minutes (0–59).

seconds

integer

Seconds (0–59).

integer

Success or failure.

Return Value
status
Return Codes
0
-1

Success.
Failure reported by operating system.

GetWindowDisplaySetting
void GetWindowDisplaySetting (int *visible, int *zoomState);
Note: This function is only available on the Windows version of LabWindows/CVI.
Purpose
Indicates how the user of your application wants the initial application window to be displayed.
The values returned by this function reflect the display options set for the program in Program
Manager and other MS Windows shells.

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Parameters
Output

visible

integer

0, if window is to be hidden;
1, if window is to be displayed.

zoomState

integer

ATTR_NO_ZOOM—normal
display;
ATTR_MINIMIZE
ATTR_MAXIMIZE.

Return Value
None
Example
If you want to honor the user’s display options, put the following code where you display your
initial panel.
int showWindow, zoomState;
GetWindowDisplaySetting (&showWindow, &zoomState);
/* load panel or create panel) */
if (showWindow){
SetPanelAttribute (panel, ATTR_WINDOW_ZOOM, zoomState);
SetPanelAttribute (panel, ATTR_VISIBLE, 1);
}

InitCVIRTE
int status = InitCVIRTE (void *hInstance, char *argv[], void *reserved);
Purpose
This function performs initialization of the CVI Run-Time Engine. It is needed only in
executables or DLLs that are linked using an external compiler. Otherwise, it is harmless.
Note: In LabWindows/CVI version 4.0.1, this function was expanded from one to three
parameters. Executables and DLLs created with the one-parameter version of the
function will continue to work properly.

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Parameters
Input

hInstance

void
pointer

0 if called from main.
hInstance if called from WinMain (first parameter).
hInstDLL if called from DllMain (first parameter).

argv

string
array

argv if called from main (second parameter).
Otherwise, 0.

reserved

void
pointer

Reserved for future use. Pass 0.

integer

1 indicates success.
0 indicates failure (probably out of memory).

Return Value
status

Using this Function
The function should be called in your main, WinMain, or DllMain function. Which of these
three functions you are using determines the parameter values you should pass to InitCVIRTE.
The following examples show how to use InitCVIRTE in each case.
int main (int argc, char *argv[])
{
if (InitCVIRTE (0, argv, 0) == 0)
return -1;
/* out of memory */
/* your other code */
return 0;
}
int __stdcall WinMain (HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpszCmdLine,
int nCmdShow)
{
if (InitCVIRTE (hInstance, 0, 0) == 0)
return -1;
/* out of memory */
/* your other code */
return 0;
}
int __stdcall DllMain (void *hinstDLL, int fdwReason,
void *lpvReserved)
{
if (fdwReason == DLL_PROCESS_ATTACH)
{
if (InitCVIRTE (hinstDLL, 0, 0) == 0)
return 0;
/* out of memory */
/* your other ATTACH code */
}
else if (fdwReason == DLL_PROCESS_DETACH)
{

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/* your other DETACH code */
CloseCVIRTE ();
}
return 1;
}

Note: The prototypes for InitCVIRTE and CloseCVIRTE are in cvirte.h, which is
included by utility.h.

inp
char byteRead = inp (int portNumber);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
Reads a byte from a port.
Note: For you to be able to use this function under Windows NT, the LabWindows/CVI lowlevel support driver must be loaded.
Parameters
Input

portNumber

integer

The port.

char

Byte read from port.

Return Value
byteRead

inpw
short wordRead = inpw (int portNumber);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
Reads a word from a port.
Note: For you to be able to use this function under Windows NT, the LabWindows/CVI lowlevel support driver must be loaded.

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Parameters
Input

portNumber

integer

The port.

short

Word read from port.

Return Value
wordRead

InStandaloneExecutable
int standalone = InStandaloneExecutable(void);
Purpose
Returns a non-zero value if your program is running as a standalone executable. If your program
is running in the LabWindows/CVI development environment, a zero is returned.
Return Value
standalone

integer

1 = Program is running as a standalone executable.
0 = Program is running as in LabWindows/CVI.

KeyHit
int result = KeyHit (void);
Purpose
Indicates whether the user has pressed a key on the keyboard.
Note: This function only detects keystrokes in the Standard I/O window. It does not detect
keystrokes in windows created with the User Interface Library or in the console
window in a Windows Console Application.
Parameters
None
Return Value
result

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Indicates if a key has been
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Return Codes
0

Key has not been pressed.

1

Key has been pressed.

Using This Function
The function returns 1 if a keystroke is available in the keyboard buffer, 0 otherwise. After a
keystroke is available, you should make a call to GetKey to flush the keyboard buffer.
Otherwise, KeyHit will continue to return 1.
Note: This function always returns 0 if you are running on UNIX and have done one of the
following.
•

•

Selected Use hosts system’s standard Input/Output in the dialog box brought up
by selecting Options » Environment in the Project window; or
Called SetStdioPort to set the port to HOST_SYSTEM_STDIO.

Example
/* flush any pending keystrokes */
while (KeyHit())
GetKey();
/* perform loop indefinitely until the user presses key */
while (!KeyHit()) {
}

LaunchExecutable
int result = LaunchExecutable (char fileName[]);
Purpose
Starts running a program and returns without waiting for it to exit. The program must be an
actual executable; that is, you cannot launch commands intrinsic to a command interpreter.
Under Microsoft Windows the executable can be either an DOS or Windows executable,
including *.exe, *.com, *.bat, and *.pif files.
If you need to execute a command built into command.com such as copy, dir, and others,
you can call LaunchExecutable with the command
command.com /C DosCommand args, where DosCommand is the shell command you
would like executed. For example, the following command string would copy file.tmp from
the temp directory to the tmp directory:
command.com /C copy c:\\temp\\file.tmp c:\\tmp

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Refer to your DOS documentation for further help with command.com. DOS executables
(.exe, .com, and .bat files) use the settings in _default.pif (in your Windows
directory) when they are running. You can change their priority, display options, and more by
editing _default.pif or by creating another .pif file. Refer to your Microsoft Windows
documentation for help on creating and editing .pif files.
Parameter
Input

fileName

string

Pathname of executable file and
arguments.

integer

Result of operation.

Return Value
result
Return Codes Under UNIX
0

Command was successfully started.

-1

The system-imposed limit on the total number of processes under execution or the
total number of processes per user would be exceeded. This limit is determined
when the system is generated.

-2

There is insufficient swap space for the new process.

-3

vfork failed for unknown reason.

-4

Search permission is denied for a directory listed in the path prefix of the new
process image file, or the new process image file denies execution permission, or
the new process image file is not a regular file.

-5

The length of the path or file, or an element of the environment variable PATH
prefixed to a file exceeds {PATH_MAX}, or a pathname component is longer than
{NAME_MAX} while {_POSIX_NO_TRUNC} is in effect for that file (see man
page for pathconf(2V)).

-6

One or more components of the pathname of the new process image file do not
exist.

-7

A component of the path prefix of the new process image file is not a directory.

-8

The number of bytes used by the new process image's argument list and
environment list is greater than {ARG_MAX} bytes (see man page for
sysconf(2V)).
The new process image file has the appropriate access permission, but is not in the
proper format.

-9

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Return Codes under Microsoft Windows
0

Command was successfully started.

-1

System was out of memory, executable file was corrupt, or relocations were invalid.

-3

File was not found.

-4

Path was not found.

-6

Attempt was made to dynamically link to a task, or there was a sharing or networkprotection error.

-7

Library required separate data segments for each task.

-9

There was insufficient memory to start the application.

-11

Windows version was incorrect.

-12

Executable file was invalid. Either it was not a Windows application or there was an
error in the .EXE image.

-13

Application was designed for a different operating system.

-14

Application was designed for MS-DOS 4.0.

-15

Type of executable file was unknown.

-16

Attempt was made to load a real-mode application (developed for an earlier version of
Windows).

-17

Attempt was made to load a second instance of an executable file containing multiple
data segments that were not marked read-only.

-20

Attempt was made to load a compressed executable file. The file must be
decompressed before it can be loaded.

-21

Dynamic-link library (DLL) file was invalid. One of the DLLs required to run this
application was corrupt.
Application requires Microsoft Windows 32-bit extensions.

-22

Parameter Discussion
fileName is the program to be run.
If the program is not in one of the directories specified in the PATH environment variable, you
must specify the full path. The path can include arguments to be passed to the program.
Under Microsoft Windows, if the program is a .pif, .bat, or .com file, the extension must be
included in the path name.
For example, under Microsoft Windows the following command string launches the Edit
program with the file file.dat.
c:\\dos\\edit.com c:\\file.dat

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LaunchExecutableEx
int result = LaunchExecutableEx (char *fileName, int windowState, int *handle);
Purpose
LaunchExecutableEx performs the same operation as LaunchExecutable with the
following extended features:
•

Under Windows, you can specify how the Windows application displays.

•

This function returns a handle to the executable that can show whether the executable is still
running and also terminate the executable.

Parameters
Input

fileName

string

Pathname of executable file and arguments.

windowState

integer

Specifies how a Windows program is to be shown.
(Ignored under UNIX).

integer

A handle representing the executable launched.

integer

Result of operation.

Output handle
Return Value
result
Return Codes
0

Success.

(non-zero value)

Failure (refer to LaunchExecutable).

Parameter Discussion
The following values are valid for windowState:
LE_HIDE
LE_SHOWNORMAL
LE_SHOWMINIMIZED
LE_SHOWMAXIMIZED
LE_SHOWNA
LE_SHOWMINNOACTIVE

application window is hidden
application window is shown normally and is activated
application window is displayed as an icon and is activated
application window is displayed as a maximized window and
is activated
application window is shown normally but is not activated
application window is shown as an icon but is not activated

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A handle can be passed to ExecutableHasTerminated and TerminateExecutable.
When you no longer need the handle, you should call RetireExecutableHandle. When
you do not want to obtain a handle, you can pass NULL.
When you launch several processes with LaunchExecutableEx but do not call
RetireExecutableHandle on them, you might reach the limit for the maximum number of
processes the system imposes. This happens even when the processes have already terminated;
the program does not recognize that the processes have terminated until you call
RetireExecutableHandle.
Checking Termination of CVI Executables Under Windows 3.1
If you launch another LabWindows/CVI executable under Windows 3.1, the launched executable
process will terminate itself after launching the new copy of the CVI Run-time Engine. If you
use ExecutableHasTerminated, the return value always will be 1 because the process
identification for the second Run-time Engine cannot be tracked. This behavior can also occur
with non-LabWindows/CVI executables.
You can work around this problem when launching LabWindows/CVI runtime executables by
executing the Run-Time Engine directly and passing it the pathname of the executable. For
example:
c:\cvi\cvirt4.exe

c:\test\myapp.exe

The pathname of the Run-Time Engine might not be c:\cvi\cvirt4.exe. You can
determine the pathname of the Run-Time Engine by looking at the [cvirt4] section in
win.ini. (If the runtime executable was made with a different version of CVI, look in the
[cvirtnn] section for that version.)
If you need to pass arguments to your application, create a file containing the arguments and pass
the pathname of that file as the second argument to the Run-Time Engine. For example:
c:\cvi\cvirt4.exe

c:\test\myapp.exe

myargs

The file containing the arguments must be in the same directory as the executable. The first three
characters in the file containing the arguments must be “CVI” in uppercase, as in the following
example:
CVI

arg1

arg2

arg3

The Run-Time Engine deletes the file containing the arguments after reading it.

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LoadExternalModule
int module_id = LoadExternalModule (char pathName[]);
Purpose
Loads a file containing one or more object modules.
Parameter
Input

pathName

string

Relative or absolute pathname
of the module to be loaded.

integer

ID of the loaded module.

Return Value
module_id
Return Codes
-1

Out of memory.

-2

File not found.

-4

Invalid file format.

-6

Invalid path name.

-7

Unknown file extension.

-8

Cannot open file.

-11

.PTH file open error.

-12

.PTH file read error.

-13

.PTH file invalid contents.

-14

DLL header file contains a static function prototype.

-15

DLL function has an unsupported argument type.

-16

DLL has a variable argument function.

-17

DLL header contains a function without a proper prototype.

-18

DLL function has an unsupported return type.

-19

A DLL function’s argument or return type is a function pointer.

-20

A function in the DLL header file was not found in the DLL.
(continues)

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Return Codes (Continued)
-21

Could not load the DLL.

-22

Could not find the DLL header file.

-23

Could not load the DLL header file (out of memory or the file is corrupted).

-24

Syntax error in the DLL header file.

-25

DLL initialization function failed.

-26

Module already loaded with different calling module handle. (See
LoadExternalModuleEx.)

-27

Invalid calling module handle. (See LoadExternalModuleEx.)

-28

Module loaded in Borland mode in the LabWindows/CVI development
environment contains uninitialized global variables that are also defined in other
modules.

Parameter Discussion
This function loads an external object module file. The file need not be listed in your project nor
loaded as an instrument module.
Under Windows 3.1, the file may be an object file (.obj), a library file (.lib), or a
dynamically linked library (.dll). Object and library modules must be compiled with the
Watcom C compiler for Windows or the LabWindows/CVI compiler.
Under Windows 95 and NT, the file may be an object file (.obj), a library file (.lib), or a
DLL import library (.lib). You cannot load a DLL directly. Object and library modules can be
compiled in LabWindows/CVI or an external compiler.
In UNIX, the file may be an object file (.o) or a statically linked library (.a).
All files must conform to the rules for loadable compiled modules in the LabWindows/CVI
Programmer Reference Manual.
By loading external object modules, you can execute code that is not in your project and not in a
loaded instrument module. You can load the external modules only when needed and unload
them when they are no longer needed.
After a module has been loaded, you can execute its code in one of two ways:
•

You can obtain pointers to functions in the module by calling
GetExternalModuleAddr. You can then call the module's functions through the
function pointers.

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•

Utility Library

You can call RunExternalModule. This requires that the module contain a function with
a pre-defined name and prototype. The function serves as the entry point to the module. See
RunExternalModule for more information.

LoadExternalModule can also be used on a source file (.c) that is part of the current
project or a source file that has been loaded as the program for an instrument module. This
allows you to develop your module in source code form and test it using the LabWindows/CVI
debugging capabilities. After you have finished testing your module and compiled it into an
external object or library file, you need to make no modifications to your application source code
other than to change the pathname in the call to LoadExternalModule.
Avoid calling LoadExternalModule on a file in the project when you plan to link your
program in an external compiler. The LabWindows/CVI Utility library does not know the
locations of symbols in executables or DLLs linked in external compilers. You can provide this
information by using the Other Symbols section of the External Compiler Support dialog box
(in the Build menu of the LabWindows/CVI Project window) to create an object module
containing a table of symbols you want to find using GetExternalModuleAddr. If you use
this method, you should pass the empty string ("") to LoadExternalModule for the module
pathname.
If successful, LoadExternalModule returns an integer module ID which can later be passed
to RunExternalModule, GetExternalModuleAddr, and UnloadExternalModule.
If unsuccessful, LoadExternalModule returns a negative error code.
Resolving External References from Object and Static Library Files on Windows 95/NT
There is an important difference between loading an object or static library module and loading a
DLL via an import library. DLLs are prelinked, that is, when an DLL is loaded, no external
references need to be resolved. Object and static library modules, on the other hand, do have
external references that need to be resolved. LoadExternalModule resolves them using
symbols defined in the project or in object, static library, or import library modules that have
already been loaded using LoadExternalModule. This is true even when you call
LoadExternalModule from a DLL. LoadExternalModule does not use symbols in a
DLL to resolve external references unless those symbols have been exported in the import
library.
When you load an object or library module from a DLL, you may want external references to be
resolved through global symbols in the DLL that have not been exported in the import library. If
this is your intention, you must call LoadExternalModuleEx rather than
LoadExternalModule.
Using This Function
pathname may be a relative or absolute pathname. If it is a simple file name (such as
module.obj), LoadExternalModule attempts to find the file as follows.
1. It first looks for the file in the project list.
2. It then looks for the file in the directory that contains the currently loaded project.

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3. If the file has not been found and its extension is .dll, LoadExternalModule searches
for the file in the directories specified in the Windows LoadLibrary call.
If it is a relative pathname with one or more directory paths (such as dir\module.obj),
LoadExternalModule creates an absolute pathname by appending the relative pathname to
the directory that contains the currently loaded project.
If the pathname is for a DLL import library, LoadExternalModule finds the DLL using the
DLL name embedded in the import library and the standard Windows DLL search algorithm.
Example
void (*funcPtr) (char buf[], double dval, int *ival);
int module_id;
int status;
char buf[100];
double dval;
int ival;
char *pathname;
char *funcname;
pathname = "EXTMOD.OBJ";
funcname = "my_function";
module_id = LoadExternalModule (pathname);
if (module_id < 0)
FmtOut ("Unable to load %s\n", pathname);
else
{
funcPtr = GetExternalModuleAddr (module_id, funcname, &status);
if (funcPtr == NULL)
FmtOut ("Could not get address of %s\n", funcname);
else
(*funcPtr) (buf, dval, &ival);
}

LoadExternalModuleEx
int moduleId = LoadExternalModuleEx (char pathName[],
void *callingModuleHandle);
Purpose
LoadExternalModuleEx loads a file containing one or more object modules. It is similar to
LoadExternalModule, except that, on Windows 95 and NT, external references in object
and library modules loaded from a DLL can be resolved using DLL symbols that are not
exported. On platforms other than Windows 95 and NT, LoadExternalModuleEx works
exactly like LoadExternalModule.

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Parameters
Input

pathName

string

Relative or absolute pathname of the module to
be loaded.

callingModuleHandle

void
pointer

Usually, the module handle of the calling DLL.
You can use __CVIUserHInst. Zero
indicates the project or executable.

integer

ID of the loaded module.

Return Value
moduleId
Return Codes
Same as the return codes for LoadExternalModule.
Using this Function
Refer to the function help for LoadExternalModule for detailed information on that
function.
When you call LoadExternalModule on an object or library module, external references
need to be resolved. They are resolved using symbols defined in the project or in object, library,
or DLL import library modules that have already been loaded using LoadExternalModule
(or LoadExternalModuleEx). This is true even if you call LoadExternalModule from
a DLL.
You may want to load an object or library module from a DLL and have the module link back to
symbols that you defined in (but did not export from) the DLL. You can do this using
LoadExternalModuleEx. You must specify the module handle of the DLL as the
callingModuleHandle parameter. You can do so by using the LabWindows/CVI pre-defined
variable __CVIUserHInst.
LoadExternalModuleEx first searches the global DLL symbols to resolve external
references. Any remaining unresolved references are resolved by searching the symbols defined
in the project or in object, library, or import library modules that have already been loaded using
LoadExternalModule (or LoadExternalModuleEx).
LoadExternalModuleEx expects the DLL to contain a table of symbols that can be used to
resolve references. If you create the DLL in LabWindows/CVI, the table is included
automatically. If you create the DLL using an external compiler, you must arrange for this table
to be included in the DLL. You can do this by creating an include file that includes all of the
symbols that need to be in this table. You can then use the External Compiler Support

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command in the Build menu of the Project Window to create an object file containing the table.
You must include this object file in the external compiler project you use to create the DLL.
LoadExternalModuleEx acts identically to LoadExternalModule if either,
•

you pass zero for callingModuleHandle, or

•

you pass __CVIUserHInst for callingModuleHandle, but you are calling the function
from a file that is in the project or your executable, rather than in a DLL, or

•

you are not running in Windows 95 or NT.

You cannot load the same external module using two different calling module handles. The
function reports an error if you attempt to load the an external module when it is already loaded
under a different module handle.

MakeDir
int result = MakeDir (char directoryName[]);
Purpose
Creates a new directory based on the specified directory name.
Note: You can create only one directory at a time.
Parameters
Input

directoryName

string

New directory name.

integer

Result of operation.

Return Value
result
Return Codes
0

Success.

-1

One of the path components not found.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-5

Invalid path (for example, c:filename in Windows).

-6

Access denied.

-8

Disk is full.

-9

Directory or file already exists with same pathname.

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Example
/* make a new directory named \DATA\WAVEFORM on drive C /*
/* assuming that C:\DATA does not exist
*/
MakeDir ("C:\\DATA");
MakeDir ("C:\\DATA\\WAVEFORM");

MakePathname
void MakePathname (char directoryName[], char fileName[], char pathName[]);
Purpose
Constructs a path name from a directory path and a filename. The subroutine ensures that the
directory path and the filename are separated by a backslash.
Parameters
Input

Output

directoryName

string

Directory path.

fileName

string

Base file name and extension.

pathName

string

Path name.

Return Value
None
Parameter Discussion
pathName must be at least MAX_PATHNAME_LEN bytes long. If the pathName constructed
from directoryName and fileName exceeds that size, an empty string is returned in pathName.
Example
char dirname[MAX_PATHNAME_LEN];
char pathname[MAX_PATHNAME_LEN];
GetProjectDir (dirname);
MakePathname (dirname, "FILE.DAT", pathname);

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outp
char byteWritten = outp(int portNumber, char byteToWrite);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
Writes a byte to a port.
Note: For you to be able to use this function under Windows NT, the LabWindows/CVI lowlevel support driver must be loaded.
Parameters
Input

portNumber

integer

The port.

byteToWrite

char

The byte to be written.

char

The byte that was written.

Return Value
byteWritten

outpw
short wordWritten = outpw (short portNumber, int wordToWrite);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
Writes a word to a port.
Note: For you to be able to use this function under Windows NT, the LabWindows/CVI lowlevel support driver must be loaded.
Parameters
Input

portNumber

integer

The port.

wordToWrite

short

The word to be written.

Return Value
wordWritten

LabWindows/CVI Standard Libraries

short

The word that was written.

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ReadFromPhysicalMemory
int status = ReadFromPhysicalMemory (unsigned int physicalAddress,
void *destinationBuffer,
unsigned int numberOfBytes);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
Copies the contents of a region of physical memory into destinationBuffer. The function does
not check whether the memory actually exists. If the memory does not exist, the success value is
returned but no data is read.
Note: For you to be able to use this function under Windows 95 or NT, the LabWindows/CVI
low-level support driver must be loaded.
Parameters
Input

physicalAddress

unsigned integer

The physical address to be read
from. There are no restrictions
on the address; it can be below
or above 1 MB.

destinationBuffer

void pointer

The buffer into which the
physical memory will be copied.

numberOfBytes

unsigned integer

The number of bytes to copy
from physical memory.

integer

Indicates whether the function
succeeded.

Return Value
status

Return Codes
1

Success.

0

Failure reported by the operating system, or low-level
support driver not loaded.

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ReadFromPhysicalMemoryEx
int status = ReadFromPhysicalMemoryEx (unsigned int physicalAddress,
void *destinationBuffer,
unsigned int numberOfBytes,
int bytesAtATime);
Note: This function is available only in the Windows version of LabWindows/CVI.
Purpose
This function copies the contents of a region of physical memory into the specified buffer. It can
copy the data in units of 1, 2, or 4 bytes at a time.
The function does not check whether the memory actually exists. If the memory does not exist,
the success value is returned but no data is read.
Note: For you to be able to use this function under Windows 95 or NT, the LabWindows/CVI
low-level support driver must be loaded.
Parameters
Input

physicalAddress

unsigned
integer

The physical address to read from. There are
no restrictions on the address; it can be above
or below 1 MB.

destinationBuffer

void pointer

The buffer into which the physical memory is
copied.

numberOfBytes

unsigned
integer

The number of bytes to copy from physical
memory.

bytesAtATime

integer

The unit size in which to copy the data. Can be
1, 2, or 4.

integer

Indicates whether the function succeeded.

Return Value
status
Return Codes
1

Success.

0

Failure reported by operating system, or low-level support driver not loaded, or
numberOfBytes is not a multiple of bytesAtATime, or invalid value for
bytesAtATime.

Parameter Discussion
numberOfBytes must be a multiple of bytesAtATime.

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ReleaseExternalModule
int status = ReleaseExternalModule (int moduleID);
Purpose
Decreases the reference count for a module loaded using LoadExternalModule.
When LoadExternalModule is called successfully on a module, that module's reference
count is incremented by one. When you call ReleaseExternalModule, its reference count
is decremented by one.
If the reference count is decreased to zero, then the module ID is invalidated and you cannot
access the module through GetExternalModuleAddr or RunExternalModule. If, in
addition, the module file is not in the project and not loaded as an instrument, the external
module is removed from memory.
If you want to unload the module regardless of the reference count, call
UnloadExternalModule rather than ReleaseExternalModule. Use
ReleaseExternalModule when multiple calls may have been made to
LoadExternalModule on the same module and you do not want to unload the module in
case it is still being used by other parts of the application.
Parameter
Input

moduleID

integer

The module ID returned by LoadExternalModule.

integer

Indicates the result of the operation.

Return Value
status
Return Codes
>0

Success, but the module was not unloaded. The value indicates the number of
remaining references.

0

Success, and the module was unloaded.

-5

The module cannot be unloaded because it is referenced by another external
module that is currently loaded.

-9

Invalid module ID.

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RenameFile
int result = RenameFile (char existingFileName[], char newFileName[]);
Purpose
Renames an existing file.
Parameters
Input

existingFileName

string

Existing file name.

newFileName

string

New file name.

integer

Result of rename operation.

Return Value
result
Return Codes
0

Success.

-1

File not found or directory in path not found.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-5

Invalid path (for either of the file names).

-6

Access denied.

-7

Specified existing path is a directory, not a file.

-8

Disk is full.

-9

New file already exists.

Parameter Discussion
existingFileName and newFileName may contain DOS wildcard characters ‘?’ and ‘*’. If
existingFileName has wildcards, all matching files are renamed. If newFileName has
wildcards, it will be matched to existingFileName.
existingFileName may be the empty string (""), in which case the file found by the most recent
call to GetFirstFile or GetNextFile is renamed.
Under Microsoft Windows, if the arguments to RenameFile specify files on different disk
drives, RenameFile copies the source to the target and then deletes the source file.

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Under UNIX, if the arguments to RenameFile specify files on different file systems,
RenameFile copies the source to the target and then deletes the source file.

RetireExecutableHandle
int status = RetireExecutableHandle (int executableHandle);
Purpose
Informs the Utility Library that you no longer intend to use the handle acquired from
LaunchExecutableEx. When you call this function the Utility Library can reuse the
memory allocated to keep track of the state of the executable.
Under UNIX, if the process has terminated, the system removes the process from the list of
processes. This keeps the system from reaching the limit on the total number of processes under
execution by a single user which the system imposes.
Parameters
Input

executableHandle

integer

The executable handle acquired from
LaunchExecutableEx.
-1 = handle is invalid.
0 = success.

integer

Result of operation.

Return Value
status

RoundRealToNearestInteger
long n = RoundRealToNearestInteger (double inputRealNumber);
Purpose
Rounds its floating-point argument and returns the result as a long integer. A value with a
fractional part of exactly 0.5 is rounded to the nearest even number. This function is encountered
in translations.
Parameter
Input

inputRealNumber

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Return Value
long

n

Result of the rounding operation.

Example
long n;
n = round
n = round
n = round
n = round
n = round
n = round
n = round
n = round

(1.2);
(1.8);
(1.5);
(0.5);
(-1.2);
(-1.8);
(-1.5);
(-0.5);

/*
/*
/*
/*
/*
/*
/*
/*

result:
result:
result:
result:
result:
result:
result:
result:

1L
2L
2L
0L
-1L
-2L
-2L
0L

*/
*/
*/
*/
*/
*/
*/
*/

RunExternalModule
int result = RunExternalModule (int moduleID, char *buffer);
Purpose
Calls the pre-defined entry point function in an external module (see LoadExternalModule).
Parameters
Input

moduleID

integer

ID of loaded module.

buffer

string

Parameter buffer.

integer

Indicates the result of the operation.

Return Value
result
Return Codes
0

Success.

-1

Out of memory.

-3

Entry point is undefined.

-4

Invalid file format.

-5

Undefined references.

-8

Cannot open file.

-9

Invalid module ID.

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Parameter Discussion
moduleID is the value LoadExternalModule returns. buffer is a character array in
which you can pass information to and from the module.
RunExternalModule requires that the module define the following function:
void _xxx_entry_point (char [])

where xxx is the base name of the file, in lowercase. For example, if the pathname of the
file is as follows:
C:\LW\PROGRAMS\TEST01.OBJ

then the name of the entry point must be:
_test01_entry_point

Example
int module_id;
int status;
char *pathname;
pathname = "EXTMOD.OBJ";
module_id = LoadExternalModule (pathname);
if (module_id <0)
FmtOut ("Unable to load %s\n", pathname);
else {
RunExternalModule (module_id, "");
UnloadExternalModule (module_id);
}

SetBreakOnLibraryErrors
int oldState = SetBreakOnLibraryErrors (int newState);
Purpose
When debugging is enabled and a National Instruments library function reports an error,
LabWindows/CVI can display a runtime error dialog box and suspend execution. You can use
this function to enable or disable this feature.
In general, it is best to use the Break on library errors checkbox in the Run Options command
of the Project window to enable or disable this feature. You should use this function only when
you want the temporarily disable the Break on library errors feature around a segment of code.
This function does not affect the state of the Break on library errors checkbox in the Run
Options command of the Project window.

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If debugging is disabled, this function has no effect. Run-time errors are never reported when
debugging is disabled.
Parameters
Input

newState

integer

Pass a nonzero value to enable. Pass zero to disable.

integer

Previous state of the break on library errors feature.

Return Value
oldState
Return Codes
1

Was previously enabled.

0

Was previously disabled, or debugging is disabled.

Example
int oldValue;
oldValue = SetBreakOnLibraryErrors (0);
/* function calls that may legitimately return errors */
SetBreakOnLibraryErrors (oldValue);

SetBreakOnProtectionErrors
int oldState = SetBreakOnProtectionErrors (int newState);
Purpose
If debugging is enabled, LabWindows/CVI uses information it gathers from compiling your
source code to make extensive run-time checks to protect your program. When it encounters a
protection error at run-time, LabWindows/CVI displays a dialog box and suspends execution.
Examples of protection errors are
•

An invalid pointer value is dereferenced in source code.

•

An attempt is made in source code to read or write beyond the end of an array.

•

A function call is made in source code in which an array is smaller than is expected by the
function.

•

Pointer arithmetic is performed in source code which generates an invalid address.

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You can use this function to prevent LabWindows/CVI from displaying the dialog box and
suspending execution when it encounters a protection error. In general, it is better not to disable
the break on protection errors feature. Nevertheless, you may want to disable it temporarily
around a line of code for which LabWindows/CVI is erroneously reporting a protection error.
If debugging is disabled, this function has no effect. Run-time errors are not reported when
debugging is disabled.
Note: If an invalid memory access generates a processor exception, LabWindows/CVI reports
the error and terminates your program regardless of the debugging level or the state of
the break on protection errors feature.
Parameters
Input

newState

integer

Pass a nonzero value to enable. Pass zero to
disable.

integer

Previous state of the break on protection errors
feature.

Return Value
oldState

Return Codes
1

Was previously enabled.

0

Was previously disabled, or debugging is disabled.

Example
int oldValue;
oldValue = SetBreakOnProtectionErrors (0);
/* the statement that erroneously reports an error */
SetBreakOnProtectionErrors (oldValue);

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SetDir
int result = SetDir (char directoryName[]);
Purpose
Sets the current working directory to the specified directory. Under Windows 3.1, this function
can change the current working directory on any drive, however it does not change the default
drive. To change the default drive, use the SetDrive function.
Parameters
Input

directoryName

string

New current working directory.

integer

Result of operation.

Return Value
result
Return Codes
0

Success.

-1

Specified directory not found or out of memory.

Parameter Discussion
Under Windows 3.1, directoryName must not contain a drive letter.

SetDrive
int result = SetDrive (int driveNumber);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
Sets the current default drive.
Parameters
Input

driveNumber

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integer

New drive number (0 to 25).

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Return Value
integer

result

Result of operation.

Return Codes
0

Success.

-1

Invalid drive number.

Using This Function
The mapping between the drive number and the logical drive letter is 0 = A, 1 = B, and so on.

SetFileAttrs
int result = SetFileAttrs (char fileName[], int read-only, int system, int hidden,
int archive);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
Sets the read-only, system, hidden and archive attributes of a file.
The read-only attribute protects a file from being overwritten and prevents the creation of a file
with the same name.
The system attribute and hidden attribute both prevent the file from appearing in a directory list
and exclude it from normal searches.
The archive attribute is set whenever the file is modified, and cleared by the DOS BACKUP
command.
Parameters
Input

fileName
read-only

string
integer

File to set attributes.
Read-only attribute.

system

integer

System attribute.

hidden

integer

Hidden attribute.

archive

integer

Archive attribute.

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Return Value
result

return value

Result of operation.

Return Codes
0
-1

Success.
One of the following errors occurred:
• File not found.
• Attribute cannot be changed.

Parameter Discussion
Each attribute parameter can have one of the following values:
0—clears the attribute
1—sets the attribute
-1—leaves the attribute unchanged
fileName may be the empty string (""), in which case the attributes of the file found by the most
recent call to GetFirstFile or GetNextFile are set.

SetFileDate
int status = SetFileDate (char fileName[], int month, int day, int year);
Purpose
Sets the date of a file.

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Parameters
Input

fileName

string

File to set attributes.

month

integer

Month (1 to 12)
1 —January
2 —February
3 —March
4 —April
5 —May
6 —June
7 —July
8 —August
9 —September
10 —October
11 —November
12 —December

day

integer

Day of month (1 to 31)

year

integer

Year (1980–2099)

integer

Result of operation.

Return Value
status
Return Codes
0

Success.

-1

File not found or directory in path not found.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-5

Invalid date, or invalid path (for example, c:filename in Windows).

-6

Access denied.

Parameter Discussion
fileName may be the empty string (""), in which case the date of the file found by the most
recent call to GetFirstFile or GetNextFile is set.

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SetFileTime
int result = SetFileTime (char fileName[], int hours, int minutes, int seconds);
Purpose
Sets the time of a file.
Parameters
Input

fileName

string

File to set date.

hours

integer

Hours (0 to 23).

minutes

integer

Minutes (0 to 59).

seconds

integer

Seconds (0-58); Odd Values are
rounded down.

integer

Result of operation.

Return Value
result
Return Codes
0

Success.

-1

File not found or directory in path not found.

-3

General I/O error occurred.

-4

Insufficient memory to complete operation.

-5

Invalid time, or invalid path (for example, c:filename in Windows).

-6

Access denied.

Parameter Discussion
fileName may be the empty string (""), in which case the time of the file found by the most
recent call to GetFirstFile or GetNextFile is set.
seconds value must be entered in increments of 2.

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SetPersistentVariable
void SetPersistentVariable (int value);
Purpose
Lets you store an integer value across multiple builds and executions of your project in the
LabWindows/CVI development environment. When you unload a project or load a new project,
the value is reset to zero.
This function is useful when your program performs an action (such as setting up your
instruments) that takes a long time and that you do not want to be repeated each time you re-run
your program. Global variables in your program are reinitialized to zero each time you run your
project. Thus, they cannot be used to indicate that you have already taken the action once.
To get around this problem, LabWindows/CVI maintains an integer variable across multiple
builds and executions of your project. This function sets the value of that variable. To retrieve
the variable value, call GetPersistentVariable().
Parameters
Input

value

integer

The value to assign to the
persistent variable.

SetStdioPort
int status = SetStdioPort (int stdioPort);
Purpose
Sets the current destination for data written to the standard output (and the source of data read
from standard input).
You can specify either the CVI Standard Input/Output window or the standard input/output of
the host system.
Note: This function is valid only on the UNIX version of LabWindows/CVI.

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Parameters
Input

stdioPort

integer

CVI_STDIO_WINDOW (0) =
the CVI Standard Input/Output
window.
HOST_SYSTEM_STDIO (1) =
the host system's standard
output.

integer

Indicates whether the function
succeeded.

Return Value
status

Return Codes
0
-2

Success.
Destination was not a valid range.

Parameter Discussion
In a standalone executable, the default value for stdioPort is CVI_STDIO_WINDOW.
In the CVI Development System, the default value for stdioPort is the current state of the Use
host system's standard input/output option in the dialog box brought up by the Environment
command in the Options menu of the Project window. The value that you set using this function
is reflected the next time you bring up the environment dialog.

SetStdioWindowOptions
int status = SetStdioWindowOptions (int maxNumLines,
int bringToFrontWhenModified,
int showLineNumbers);
Purpose
Sets the current value of the following Standard Input/Output window options:
Maximum Number of Lines
Bring To Front When Modified
Show Line Numbers

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Parameters
Input

maxNumLines

integer

bringToFrontWhenModified

integer

showLineNumbers

integer

The maximum number of lines
that can be stored in the
Standard Input/Output Window.
If this amount is exceeded, lines
are discarded from the top.
Valid range: 100 to 1000000.
Indicates whether the Standard
Input/Output window is brought
to the front each time a string or
character is added to it.
1 = Yes.
0 = No.
Indicates whether line numbers
are shown in the Standard
Input/Output window.
1 = Yes.
0 = No.

Return Value
status

integer

Indicates whether the function
succeeded.

Return Codes
0
-1

Success.
Maximum number of lines is not within the valid
range.

Parameter Discussion
maxNumLines—In an executable, the default value is 10000. In the CVI Development System,
the default value is the value set in the dialog box brought up by the Environment command in
the Options menu of the Project window. The value that you set using this function is reflected
the next time you bring up the Environment dialog box.
bringToFrontWhenModified—In an executable, the default value is 1 ("bring to front when
modified"). In the CVI Development System, the default value is the current state of the "Bring
Standard Input/Output window to front whenever modified" option in the dialog box brought up
by the Environment command in the Options menu of the Project window. The value that you
set using this function is reflected the next time you bring up the Environment dialog box.

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showLineNumbers—In an executable, the default value is 0 ("do not show line numbers"). In
the CVI Development System, the default value is the current state of the Line Numbers option
in the View menu of the Standard Input/Output Window. The value that you set using this
function is reflected the next time you bring up the View menu.

SetStdioWindowPosition
int status = SetStdioWindowPosition (int top, int left);
Purpose
Sets the current position, in pixels, of the client area of the Standard Input/Output window
relative to the upper left corner of the screen. The client area begins under the title bar and to the
right of the frame.
Parameters
Input

top

integer

left

integer

The distance, in pixels, of the top of client
area of the Standard Input/Output window
relative to the top of the screen.
Valid Range: VAL_AUTO_CENTER
-16000 to +16000.
The distance, in pixels, of the leftmost edge of
client area of the Standard Input/Output
window relative to the leftmost edge of the
screen.
Valid Range: VAL_AUTO_CENTER
-16000 to +16000.

Return Value
status

integer

Indicates whether the function succeeded.

Return Codes
0
-1

Success.
top is not within the valid range.

-2

left is not within the valid range.

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Parameter Discussion
To vertically center the Standard Input/Output window client area within the area of the screen,
pass VAL_AUTO_CENTER as the top parameter.
To horizontally center the Standard Input/Output window client area within the area of the
screen, pass VAL_AUTO_CENTER as the left parameter.

SetStdioWindowSize
int status = SetStdioWindowSize (int height, int width);
Purpose
Sets the height and width, in pixels, of the client area of the Standard Input/Output window. The
client area excludes the frame and the title bar.
Parameters
Input

height

integer

width

integer

The height, in pixels, of the client area of the
Standard Input/Output window.
Valid Range: 0 to 16000.
The width, in pixels, of the client area of the
Standard Input/Output window.
Valid Range: 0 to 16000.

Return Value
status

integer

Indicates whether the function succeeded.

Return Codes
0
-1

Success.
height is not within the valid range.

-2

width is not within the valid range.

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SetStdioWindowVisibility
void SetStdioWindowVisibility (int visible);
Purpose
Either brings to the front or hides the Standard Input/Output window.
Parameters
Input

visible

integer

1 = Standard I/O window is visible.
0 = Standard I/O window is hidden.

SetSystemDate
int status = SetSystemDate (int month, int day, int year);
Note: This function is only available on the Windows version of LabWindows/CVI. Under
Windows NT, you must have system administrator status to use this function.
Purpose
Sets the system date.
Parameters
Input

month

integer

Month (1–12).

day

integer

Day of month (1–31).

year

integer

Year (Under Windows 3.1, the year is limited to
the values 1980–2099).

integer

Success or failure.

Return Value
status
Return Codes
0

Success.

-1

Failure reported by operating system, probably due to invalid parameter.

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SetSystemTime
int status = SetSystemTime(int hours, int minutes, int seconds);
Note: This function is only available on the Windows version of LabWindows/CVI. Under
Windows NT, you must have system administrator status to use this function.
Purpose
Sets the system time.
Parameters
Input

hours

integer

Hours (0–23).

minutes

integer

Minutes (0–59).

seconds

integer

Seconds (058). Odd values are
rounded down.

integer

Success or failure.

Return Value
status
Return Codes
0
-1

Success.
Failure reported by operating system, probably due to
an invalid parameter.

SplitPath
void SplitPath (char pathName[], char driveName[], char directoryName[],
char fileName[]);
Purpose
Splits a path name into the drive name, the directory name, and the file name.

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Parameters
Input

pathName

string

Path name to be split.

Output

driveName

string

Drive name.

directoryName

string

Full directory path, ending with
directory separator character.

fileName

string

Simple file name.

Return Value
None
Parameter Discussion
The driveName, directoryName, and fileName parameters can each be NULL. If not NULL,
they must be buffers of the following size or greater.
drive name
directory name
file name

MAX_DRIVENAME_LEN
MAX_DIRNAME_LEN
MAX_FILENAME_LEN

On operating systems without drive names (such as UNIX), driveName will always be filled in
with the empty string.
Example
char pathName[MAX_PATHNAME_LEN];
char driveName[MAX_DRIVENAME_LEN];
char dirName[MAX_DIRNAME_LEN];
char fileName[MAX_FILENAME_LEN];
SplitPath (pathName, driveName, dirName, fileName);
/*
If pathName contains
c:\cvi\samples\apps\update.c
then
“c:”
driveName contains
“\cvi\samples\apps\”
dirName contains
“update.c”
fileName contains
If pathName is
\\computer\share\dirname\foo.c
then
drive name is
""
directory name is
" \\computer\share\dirname\"
file name is
"foo.c"
*/

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SyncWait
void SyncWait (double beginTime, double interval);
Purpose
Waits until the number of seconds indicated by interval have elapsed since beginTime.
Parameters
Input

beginTime
interval

double-precision
double-precision

Value returned by Timer.
Number of seconds to wait after
begin_time.

Parameter Discussion
beginTime must be a value returned by the Timer function.
The resolution on Windows is normally 1 millisecond. However, if the following line appears
in the CVI section of your WIN.INI file, the resolution is 55 milliseconds.
useDefaultTimer = True
The resolution on Sun Solaris is 1 millisecond.
Return Value
None

SystemHelp
int status = SystemHelp (char helpFile[], unsigned int command,
unsigned long additionalLongData,
char additionalStringData[]);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
Starts Windows Help (WINHELP.EXE) and passes optional data indicating the nature of the help
requested by the application. The application specifies the path of the help file that the
application is to display.
For information about creating help files, see the Microsoft Windows Programming
Documentation (not included with LabWindows/CVI).

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Parameters
Input

helpFile

string

Points to a string containing the
help file that the Help
application is to display.
Specifies the type of help
requested.

command

unsigned integer

additionalLongData

unsigned long
integer

This value parameter depends
on the command parameter as
described in the Parameter
Discussion.

additionalStringData

string

This value parameter depends
on the command parameter as
described in the Parameter
Discussion.

integer

Non-zero on success, zero on
failure.

Return Value
status

Parameter Discussion
helpFile contains a filename that may be followed by an angle bracket (<) and the name of a
secondary window if the topic is to be displayed in a secondary window rather than in the
primary window. The name of the secondary window must have been defined in the [WINDOWS]
section of the Help Project (.HPJ) file.
command can be one of the following values:
HELP_COMMAND—Execute a Help Macro. In this case, additionalStringData is the Help
macro to be executed.
HELP_CONTENTS—Displays the Help contents topic as defined by the Contents option in the
[OPTIONS] section of the .HPJ file.
HELP_CONTEXT—Display Help for a particular topic identified by a context number that has
been defined in the [MAP] section of the .HPJ file. In this case, additionalLongData is the
context number of the topic.
HELP_CONTEXTNOFOCUS—Display Help for a particular topic identified by a context number
that has been defined in the [MAP] section of the .HPJ file. Help does not change the focus to
the window displaying the topic.

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HELP_CONTEXTPOPUP—Displays in a pop-up window a particular Help topic identified by a
context number that has been defined in the [MAP] section of the .HPJ file. The main help
window is not displayed. In this case, additionalLongData is the context number of the topic.
HELP_HELPONHELP—Displays the contents topic of the designated Using Help file.
HELP_KEY—Displays the topic in the keyword list that matches the keyword passed in the
additionalStringData parameter if there is one exact match. If there is more than one match, it
displays the first topic found. If there is no match it displays an error message.
HELP_PARTIALKEY—Displays the topic found in the keyword list that matches the keyword
passed in the additionalStringData parameter if there is one exact match. If there is more than
one match, displays the Search dialog box with the topics listed in the Go To list box. If there is
no match, it displays the Search dialog box. If you just want to bring up the Search dialog box
without passing a keyword, you should use a pointer to an empty string ("").
HELP_POPUPID—Displays in a pop-up window the topic identified by a context string. The
main window help is not displayed.
HELP_QUIT—Closes the help file. It will have no effect if the help file was opened by another
executable.
HELP_SETCONTENTS—Determines which Contents topic Help should display when the user
chooses the Contents button in Help. This call should never be used with HELP_CONTENTS. If
a Help file has two or more Contents topics, the application must assign one as the default. To
ensure that the correct Contents topic remains set, the application should call SystemHelp()
with command set to HELP_SETCONTENTS and the additionalLongData parameter
specifying the corresponding context identifier.

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TerminateExecutable
int status = TerminateExecutable (int executableHandle);
Purpose
Attempts to terminate an executable if it has not already terminated.
Under Windows the system terminates an executable by sending close messages to each window
in the application. If the application does not honor the close messages, then the application does
not terminate. The TerminateExecutable function gives up control for a limited period to
give the application an opportunity to process the close messages. This period should be
sufficient for all applications. When you need to allow more time, your program can call the
ProcessSystemEvents function in a loop, as shown in the following example.
Example
#define TIME_LIMIT 5.0 /* number of seconds */
double startTime;
startTime = Timer ();
TerminateExecutable (handle);
while (!ExecutableHasTerminated(handle)
&& (Timer()-startTime > TIME_LIMIT))
ProcessSystemEvents();

Under UNIX, you can allow more time by sending the SIGKILL message to the process. The
SIGKILL message cannot be blocked, caught, or ignored, and therefore should always succeed.
Parameters
Input

executableHandle

integer

The executable handle acquired from
LaunchExecutableEx.

Return Value
status

integer

Result of operation.

Return Codes
-1

Handle is invalid.

0

Handle is invalid.

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Timer
double t = Timer (void);
Purpose
Returns the number of seconds that have elapsed since the first call to Timer, Delay, or
SyncWait or the first operation on a timer control. The value is never reset to zero except
when you restart your program. The resolution on Windows is normally 1 millisecond.
However, if the following line appears in the CVI section of your WIN.INI file, the
resolution is 55 milliseconds.
useDefaultTimer = True

The resolution on Sun Solaris is 1 millisecond.
Parameters
None
Return Value
t

double-precision

Number of seconds since first
call to Timer.

TimeStr
char *s = TimeStr (void);
Purpose
Returns an 8-character string in the form HH:MM:SS, where HH is the hour, MM is in minutes,
and SS is in seconds.
Parameters
None
Return Value
s

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TruncateRealNumber
double y = TruncateRealNumber (double inputRealNumber);
Purpose
Truncates the fractional part of inputRealNumber and returns the result as a real number.
Parameters
Input

inputRealNumber

double-precision.

Return Value
double-precision

y

Value of inputRealNumber
without its fractional part.

UnloadExternalModule
int status_id = UnloadExternalModule (int moduleID);
Purpose
Unloads an external module file loaded via LoadExternalModule.
Parameter
Output

moduleID

integer

ID of loaded module.

integer

Indicates the result of the
operation.

Return Value
status_id

Return Codes
0
-9

Success.
Failure due to invalid module_id.

Parameter Discussion
moduleID is the value returned by LoadExternalModule, or -1. If -1 is used, all
external modules are unloaded.
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Example
int module_id;
int status;
char *pathname'
pathname = "PROG.OBJ";
module_id = LoadExternalModule (pathname);
if (module_id <0)
FmtOut ("Unable to load %s\n", pathname);
else {
RunExternalModule (module_id, "");
UnloadExternalModule (module_id);
}

WriteToPhysicalMemory
int status = WriteToPhysicalMemory (unsigned int physicalAddress,
void *sourceBuffer,
unsigned int numberOfBytes);
Note: This function is available only on the Windows versions of LabWindows/CVI.
Purpose
Copies the contents of destinationBuffer into a region of physical memory. The function does
not check whether the memory actually exists. If the memory does not exist, the success value is
returned but no data is read.
Note: For you to be able to use this function under Windows 95 or NT, the LabWindows/CVI
low-level support driver must be loaded.
Parameters
Input

physicalAddress

unsigned integer

The physical address to be written
to. There are no restrictions on
the address; it can be below or
above 1 MB.

sourceBuffer

void pointer

The buffer from which the
physical memory will be copied.

numberOfBytes

unsigned integer

The number of bytes to copy to
physical memory.

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Return Value
status

integer

Indicates whether the function
succeeded.

Return Codes
1
0

Success.
Failure reported by the operating system, or low-level
support driver not loaded.

WriteToPhysicalMemoryEx
int status = WriteToPhysicalMemoryEx (unsigned int physicalAddress,
void *sourceBuffer,
unsigned int numberOfBytes,
int bytesAtATime);
Note: This function is available only in the Windows version of LabWindows/CVI.
Purpose
This function copies the contents of the specified buffer to a region of physical memory. It can
copy the data in units of 1, 2, or 4 bytes at a time.
The function does not check whether the memory actually exists. If the memory does not exist,
success is returned but no data is written.
Note: For you to be able to use this function on Windows 95 or NT, the LabWindows/CVI
low-level support driver must be loaded.
Parameters
Input

physicalAddress

unsigned
integer

The physical address to write to. There are no
restrictions on the address; it can be above or
below 1 MB.

sourceBuffer

void pointer

The buffer from which the physical memory is
written.

numberOfBytes

unsigned
integer

The number of bytes to copy to physical memory.

bytesAtATime

integer

The unit size in which to copy the data. Can be 1,
2, or 4.

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Return Value
integer

status

Indicates whether the function succeeded.

Return Codes
1

Success.

0

Failure reported by operating system, or low-level support driver not loaded, or
numberOfBytes is not a multiple of bytesAtATime, or invalid value for
bytesAtATime.

Parameter Discussion
numberOfBytes must be a multiple of bytesAtATime.

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X Property Library
_____________________________________________________________________________
This chapter describes the functions in the Lab/Windows CVI X Property Library. The X
Property Library contains functions that read and write properties to and from X Windows. The
X Property Library Overview section contains general information about the X Property Library
functions and panels. The X Property Library Function Reference section contains an
alphabetical list of function descriptions.
These functions provide a mechanism for communication among X clients. This library provides
capabilities similar to those available in the TCP library, but differs from the TCP library in the
following significant ways.
•

It conforms to a conventional method for X interclient communication.

•

It works between any X clients that are connected to the same display, and does not require
any particular underlying communication protocol such as TCP.

•

It provides a method for sharing data among X clients without explicit point-to-point
connections between them.

The X Property Library Overview section contains general information about the X Property
Library. The X Property Library Function Reference section alphabetically lists function names,
with descriptions.

X Property Library Overview
The X Property Library is available only in the UNIX versions of LabWindows/CVI. This
section contains general information about the X Property Library functions and panels.

The X Property Library Function Panels
The X Property Library function panels are grouped in a tree structure according to the types of
operations performed. The X Property Library Function tree appears in Table 9-1.
The first- and second-level bold headings in the tree are the names of function classes and
subclasses. Function classes and subclasses are groups of related function panels. The thirdlevel headings in plain text are the names of individual function panels. Each X Property Library
function panel generates an X Property Library function call. The name of the function is in bold
italics to the right of the function panel name.

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Table 9-1. The X Property Library Function Tree
Accessing Remote Hosts
Connect To X Server
Disconnect From X Server
Managing Property Types
Create New Property Type
Get Property Type Name
Get Property Type Size
Get Property Type Unit
Destroy Property Type
Managing Property Information
Create New Property
Get Property Name
Get Property Type
Destroy Property
Accessing Window Properties
Get Single Window Property Item
Put Single Window Property Item
Get Window Property Value
Put Window Property Value
Remove Window Property
Handling Property Events
Install Property Callback
Uninstall Property Callback
Get Error String

ConnectToXDisplay
DisconnectFromXDisplay
CreateXPropType
GetXPropTypeName
GetXPropTypeSize
GetXPropTypeUnit
DestroyXPropType
CreateXProperty
GetXPropertyName
GetXPropertyType
DestroyXProperty
GetXWindowPropertyItem
PutXWindowPropertyItem
GetXWindowPropertyValue
PutXWindowPropertyValue
RemoveXWindowProperty
InstallXPropertyCallback
UninstallXPropertyCallback
GetXPropErrorString

X Interclient Communication
X applications often use X properties to communicate with each other. Properties are essentially
tagged data associated with a window. Applications communicate by reading and writing
properties to and from windows. In addition, an X application can request that the X server
notify it whenever a specific property value changes on a window.
The X applications that need to communicate with each other must first connect to the same X
display. Then they must agree upon the names and types of properties as well as the X window
IDs that they use to transfer the data. Although it is a simple matter to agree upon the names and
types of properties in advance, the window IDs cannot be known in advance because they are
different for each invocation of the program. There must be a mechanism for transferring the
window IDs from one client to another. A client usually accomplishes this by placing a property
that contains the window ID on the root window, which is a window that all clients can access.
The window ID refers to the window containing the data for transfer to other clients. The other
clients read this property from the root window to determine where the data is stored.

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With the LabWindows/CVI X Property Library functions, you can connect to X displays and
obtain the root window ID, read and write properties on windows, and monitor when specific
properties change.

Property Handles and Types
Before you can read or write properties on windows, you must create the property and its type.
The function CreateXProperty takes a property name and a property type and returns a
property handle you can use to access properties on windows. The property type, created by the
function CreateXPropType, contains the attributes that determine how data for the property
are stored and retrieved. More specifically, these attributes are the size and unit. The size is the
number of bytes in a single property item. The unit is the number of bytes in the basic entities
that make up a property item. See the description of CreateXPropType for more information
on the meanings of the size and unit attributes.
Table 9-2 lists the three predefined property types that you do not have to create. These types are
useful for defining properties to store X window IDs, integers, and strings.
Table 9-2. Predefined Property Types
Property Type
WINDOW_X_PROP_TYPE
INTEGER_X_PROP_TYPE
STRING_X_PROP_TYPE

Name
"WINDOW"
"INTEGER"
"STRING"

Size/Unit
sizeof(WindowX)
sizeof(int)
sizeof(char)

Communicating with Local Applications
You can use the function ConnectToXDisplay to connect to any X server on a network.
However, if your program communicates only with other applications connected to the same
display as LabWindows/CVI, you do not need to connect to the display using
ConnectToXDisplay. Instead, use the global variable CVIXDisplay, which is a pointer to
the X display that LabWindows/CVI uses. The variable CVIXRootWindow contains the
X window ID of the root window of the display that LabWindows/CVI uses.

The Hidden Window
Before you can read or write property data, you need the X window IDs of the windows that will
have the properties associated with them.
One option is to always use the root window ID for attaching properties. You could get the root
window ID for the local display from the variable CVIXRootWindow. To get the root window
ID for a remote display you could use the value returned by ConnectToXDisplay. This
approach has disadvantages. First, if your program adds a property to the root window and does

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not delete it, the property remains there indefinitely. Second, because there is only one root
window, there may be conflicts when multiple applications attempt to access the same properties.
To overcome those disadvantages, LabWindows/CVI provides a hidden window. Before it runs
your program, LabWindows/CVI creates a window that never displays. The X window ID for
this window is available in the X Property Library from the global variable
CVIXHiddenWindow. This window ID is always available to your program for reading and
writing properties. When your program terminates, LabWindows/CVI removes the window and
all of its properties.

Property Callback Functions
You can use the X Property Library to instruct LabWindows/CVI to notify your program
whenever a property (or set of properties) on a window (or set of windows) changes. The
function InstallPropertyCallback registers a function that is called whenever any of the
specified properties changes. The callback function must have the type
PropertyCallbackTypeX as defined in xproplib.h. LabWindows/CVI passes the X
display, window, and property that changed to the callback function. The state parameter of the
callback function will be either NewValueX, if the property value changed, or DeleteX, if the
property was deleted. The function UninstallPropertyCallback disables the callback
function.

Error Codes
PropLibXErrType is the data type of all return values in the X Property Library functions.
PropLibXErrType is an enumerated (enum) type containing descriptive constant names and
numeric values for the errors. PropLibXErrType and its enumerated values are all integers.
All error values are negative numbers.
The following table lists all the enumerated constant names and their corresponding numeric
values. Detailed descriptions of these error types appear in the function descriptions in the
following section.

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Table 9-3. X Property Library Error Types and Descriptions
Constant Name
NoXErr

Value

Description

0

The function was successful.

InvalidParamXErr

-1

The value passed to one or more of the parameters
was invalid. Refer to each function description for
specific information.

InvalidDisplayXErr

-2

The display argument is not a valid display. The
value for this argument must either be the value
returned by ConnectToXDisplay or be the
predefined value CVIXDisplay.

InvalidWindowXErr

-3

The window argument is not a valid window.
InstallXPropertyCallback—One or more
of the windows in the windowList argument are not
valid.

InvalidPropertyXErr

-4

The property argument is not a valid property
handle. This argument must be the value returned
by CreateXProperty.
InstallXPropertyCallback—One or more
of the property handles in the propertyList
argument are not valid.

InvalidPropTypeXErr

-5

The propertyType argument is not a valid property
type. This value must either be one of the
predefined property types or be a value returned by
CreateXPropType.

TooManyConnectionsXErr -6

The program has already made the maximum
number of connections as defined by the constant
MAX_X_DISPLAYS. Use
DisconnectFromXDisplay to allow more
connections.

CannotConnectXErr

-7

The connection could not be made to the X server.
This happens for a number of reasons including an
invalid display name, a network problem, or a
security problem.

DupPropertyXErr

-8

A property with the same propertyName, but with
different propertyType already exists.
(continues)

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Table 9-3. X Property Library Error Types and Descriptions (Continued)
DupPropTypeXErr

-9

A property type with the same typeName, but with
different size or unit already exists.

PropertyInUseXErr

-10

A property callback was installed with
InstallPropertyCallback for this property.
It is not possible to destroy properties for which
callbacks are installed.

PropTypeInUseXErr

-11

There is a property created by
CreateXProperty that has this property type. It
is not possible to destroy property types if there are
properties that use them.

TypeMismatchXErr

-12

The actual X type of the property value on the
window does not match the type specified for
property.

UnitMismatchXErr

-13

The actual X format of the property value on the
window does not match the unit specified for
property.

InvalidIndexXErr

-14

The index specified is larger than the actual number
of property items on the window.

SizeMismatchXErr

-15

The number of bytes in the property value is not a
multiple of the size specified for property.

OverflowXErr

-16

Arithmetic overflow occurred with calculations
involving the property item sizes and the number of
items specified.

InvalidCallbackXErr

-17

The function specified is not installed as a callback.

MissingPropertyXErr

-18

The property does not exist on the window.

InsuffMemXErr

-19

There is insufficient memory to perform the
operation.
CreateXProperty—There is insufficient
memory to store the property information or there
are already 256 properties.
CreateXPropType—There is insufficient
memory to store the property information or there
are already 64 property types.

GeneralXErr

-20

An Xlib function failed for an unknown reason.

BrokenConnectionXErr

-21

The connection to the X server was broken. This
occurs if the remote server terminated.

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Using the Library Outside of LabWindows/CVI
You can use the LabWindows/CVI X Property Library in applications developed outside of
LabWindows/CVI. By linking your program with the library file libxprop.a in the
misc/lib directory of the LabWindows/CVI installation directory, you can use all the
functions of the X Property Library in your program. You cannot use the libxprop.a library
within LabWindows/CVI. The following two functions are available only outside of
LabWindows/CVI:
• void _InitXPropertyLib(DisplayPtrX cviDisplay, WindowX rootWindow,
WindowX hiddenWindow)
This function sets the global variables CVIXDisplay, CVIXRootWindow,
CVIXHiddenWindow of the X Property Library.
• void HandlePropertyNotifyEvent(EventPtrX event)
This function calls the functions that are installed as property callbacks. You should call this
function whenever you receive an XPropertyNotify event to automatically invoke
callback functions. The event must be a valid XPropertyEvent.

X Property Library Function Reference
This section describes the functions in the LabWindows/CVI X Property Library. The
LabWindows/CVI X Property functions are arranged alphabetically.

ConnectToXDisplay
PropLibXErrType status = ConnectToXDisplay (const char *displayName,
DisplayPtrX *display,
WindowX *rootWindow);
Purpose
Connect to a remote X server.
Use this function to access an X server on a remote computer. This function returns a display
pointer and the root window, which you can use to read and write properties on the root window
of the remote X server.
If you want to communicate only with applications using the same display as your application,
you do not need this function. Instead, use the global variables CVIXDisplay and
CVIXRootWindow, which contain the display and root window of the X server used by
LabWindows/CVI.

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Parameters
Input

displayName

Output display

rootWindow

string

Determines the X server connection and
which communication domain to use.

DisplayPtrX
(passed by
reference)

Pointer to the display of the remote X server.
Use this value as the argument to other
library functions to communicate with the
remote X server.

WindowX
(passed by
reference)

Root window of the remote X server. Use
this value as the parameter to other library
functions to access properties on the root
window of the remote X server.

Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. status values are shown in the following table.
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to one or more of the parameters.

TooManyConnectionsXErr

-6 The program has already made the maximum
number of connections as defined by the constant
MAX_X_DISPLAYS. Use
DisconnectFromXDisplay to allow more
connections.

CannotConnectXErr

-7 The connection could not be made to the X server.
This happens for a number of reasons including an
invalid display name, a network problem, or a
security problem.

Parameter Discussion
Valid values for displayName include any valid arguments to the Xlib function
XOpenDisplay. The format is hostname:server or hostname:server.screen,
where:
•

hostname specifies the name of the host computer on which the display is physically
connected.

•

server specifies the number of the server on its host computer (usually 0).

•

screen specifies the number of the default screen on the server (usually 0).

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See Also
Refer to the Xlib Programming Manual or to Xlib—C Language X Interface, MIT X Consortium
Standard for more information about the XOpenDisplay and DefaultRootWindow
functions.
_____________________________________________________________________________

CreateXProperty
PropLibXErrType status = CreateXProperty (const char *propertyName,
PropTypeHandleX propertyType,
PropertyHandleX *property);
Purpose
Create X property information.
Use this function to define the attributes of the properties that you read and write on X windows.
You must create properties with this function before you can access them on X windows.
Each property has a unique name and a type (created by CreateXPropType) that you cannot
change except by destroying the property and recreating it.
Note: You can create a maximum of 256 different properties.
Parameters
Input

propertyName string

propertyType

Output property

Name of the property. Each property
name is unique and has a type, which
cannot be changed once the property is
created.

PropTypeHandleX

Type of the property. This value must be
either a predefined type or a value returned
by CreateXPropType.

PropertyHandleX
(passed by reference)

Handle to the property information
created. Use this value as the parameter to
other library functions to access the
property on X windows.

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Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to one or more of the parameters.

InvalidPropTypeXErr

-5 The propertyType argument is not a valid property type.
This value must either be one of the predefined property
types or be a value returned by CreateXPropType.

DupPropertyXErr

-8 A property with the same propertyName, but with
different propertyType already exists.

InsuffMemXErr

-19 There is insufficient memory to store the property
information or there are already 256 properties.

Parameter Discussion
propertyType is added with the property the first time you write a property to a window. When
you access a property on a window on which the property already exists, its type must match this
value for the access to succeed.
See Also
Refer to the Xlib Programming Manual or to Xlib—C Language X Interface, MIT X Consortium
Standard for more information about the XInternAtom function.
_____________________________________________________________________________

CreateXPropType
PropLibXErrType status = CreateXPropType (const char *typeName,
unsigned int size, unsigned int unit,
PropTypeHandleX *propertyType);
Purpose
Creates X property type. You can use this function to define the attributes of the properties that
you read and write on X windows. You must create property types with this function before you
can create properties.
Each property type has a unique name and set of attributes that cannot be changed except by
destroying the property and recreating it.

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There are three predefined property types that you do not need to create using this function.
These types, listed below, are useful for defining properties to store window IDs, integers and
strings.
Property Type
WINDOW_X_PROP_TYPE
INTEGER_X_PROP_TYPE
STRING_X_PROP_TYPE

Name
"WINDOW"
"INTEGER"
"STRING"

Size/Unit
sizeof(WindowX)
sizeof(int)
sizeof(char)

Note: You can create a maximum of 64 different property types.
Parameters
Input

typeName

string

Name of the property type. Each
property type name is unique and has
one set of attributes, which cannot be
changed after you create the property
type.

size

unsigned integer

Number of bytes in a single property
item.

unit

unsigned integer

Number of bytes in the basic units that
make up a property item.

PropTypeHandleX
(passed by reference)

Property type created. Use this value as
the type parameter to
CreateXProperty to create
properties.

Output propertyType

Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. status values are shown in the following table.
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to one or more of the parameters; size
argument is 0; unit is not 1, 2, or 4; or size is not a multiple
of unit.

DupPropTypeXErr

-9 A property type with the same typeName, but with
different size or unit already exists.

InsuffMemXErr

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Parameter Discussion
Usually, you can use the expression sizeof(TYPE) for the size parameter, where TYPE is the
C data type (char, int, and others) used to store the property value. This value must be a
multiple of the unit argument.
unit specifies how the X server should view the property item (as an array of 1-byte, 2-byte or
4-byte objects) and is necessary to perform simple byte-swapping between different types of
computers. See the notes near the end of this function description.
If the property item consists of a single object, such as an integer or a character, the unit should
be just the size of the object. An exception is the double type, for which the default unit
should be 4 bytes.
If the property item is a structure or array containing a number of smaller objects, then the unit
should be the number of bytes in the smaller objects.
Note: If you are communicating with a remote X server on a computer that has different
byte-ordering than your application, the unit specified is used to perform the byte
swapping. However, byte swapping cannot be properly performed for structures
containing different size members or for double type. For these special cases, use a
unit of 1 and then explicitly perform byte swapping where needed.
Note: The LabWindows/CVI X Property Library specifies units in the number of BYTES as
opposed to BITS. Thus, the "format" values of 8, 16 and 32 used by Xlib functions
correspond to units of 1, 2 and 4, respectively in the functions of the LabWindows/CVI
X Property Library.
See Also
Refer to the Xlib Programming Manual or to Xlib—C Language X Interface, MIT X Consortium
Standard for more information about the XInternAtom function.

DestroyXProperty
PropLibXErrType status = DestroyXProperty (PropertyHandleX property);
Purpose
Destroys X property information. You can use this function when you no longer need to access a
property. This function frees memory allocated by CreateXProperty. The property handle
cannot be used after this function is called.
All property information is destroyed when the program terminates.
Note: It is not possible to destroy properties for which callbacks are installed.

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Parameter
Input

property

PropertyHandleX

Handle to the property information to be
destroyed. This value must either be one
of the predefined property types or be a
value returned by CreateXPropType.

Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0 The function was successful.

InvalidPropertyXErr

PropertyInUseXErr

-4 The property argument is not a valid property. This
argument must be the value returned by
CreateXProperty.
-10 A property callback was installed with
InstallPropertyCallback for this property.

_____________________________________________________________________________

DestroyXPropType
PropLibXErrType status = DestroyXPropType (PropTypeHandleX propertyType);
Purpose
Destroys X property type. You can use this function when you no longer need a property type.
This function frees memory that was allocated by CreateXPropType. The property type
cannot be used after this function is called.
All property types are destroyed when the program terminates.
Note: It is not possible to destroy property types if there are properties that use them.
Parameter
Input

propertyType

PropertyHandleX Handle of the property type to be destroyed.
This value must either be one of the
predefined property types or be a value
returned by CreateXPropType.

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Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0 The function was successful.

InvalidPropTypeXErr

PropTypeInUseXErr

-5 The propertyType argument is not a valid property type.
This value must either be one of the predefined property
types or be a value returned by CreateXPropType.
-11 There is a property created by CreateXProperty that
has this property type.

DisconnectFromXDisplay
PropLibXErrType status = DisconnectFromXDisplay (DisplayPtrX display);
Purpose
Disconnects from a remote X server. You can use this function to end access to a remote
X server you connected using ConnectToXDisplay. After this function is called, you can no
longer access the remote X server.
Parameter
Input

display

DisplayPtrX

A pointer to the display of the remote
X server to be disconnected. This value
must have been obtained from
ConnectToXDisplay.

Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to the parameter.

InvalidDisplayXErr

-2 The display argument is not a valid display. This value
must be the value returned by ConnectToXDisplay.

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See Also
Refer to the Xlib Programming Manual or to Xlib—C Language X Interface, MIT X Consortium
Standard for more information about the XCloseDisplay function.

GetXPropErrorString
char *message = GetXPropErrorString (PropLibXErrType errorNum)
Purpose
Converts the error number returned by an X Property Library function into a meaningful error
message.
Parameters
Input

PropLibXErrType Status returned by an X Property
function.

errorNum

Return Value
string

message

Explanation of error.

____________________________________________________________________________________________

GetXPropertyName
PropLibXErrType status = GetXPropertyName (PropertyHandleX property,
char **propertyName);
Purpose
Gets a property name. This function returns a pointer to the name associated with the property
handle.
Parameters
Input

property

Output propertyName

PropertyHandleX Property handle for which the name is to
be obtained. This value must have been
obtained from CreateXProperty.
character pointer
(passed by reference)

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Warning:

Chapter 9

The propertyName pointer points to memory allocated by CreateXProperty.
You must not attempt to free this pointer or to change its contents.

Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to the name parameter.

InvalidPropertyXErr

-4 The property argument is not a valid property handle. This
argument must be the value returned by
CreateXProperty.

_____________________________________________________________________________

GetXPropertyType
PropLibXErrType status = GetXPropertyType (PropertyHandleX property,
PropTypeHandleX *propertyType);
Purpose
Gets the type of a property.
This function returns a pointer to the type associated with the property handle.
Parameters
Input

property

Output propertyType

PropertyHandleX Property handle for which the name is to
be obtained. This value must have been
obtained from CreateXProperty.
PropTypeHandleX The property type. Use the functions
(passed by reference) GetXPropTypeName,
GetXPropTypeSize, and
GetXPropTypeUnit to get more
information about the property type.

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Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to the parameter.

InvalidPropertyXErr

-4 The property argument is not a valid property handle. This
argument must be the value returned by
CreateXProperty.

GetXPropTypeName
PropLibXErrType status = GetXPropTypeName (PropTypeHandleX propertyType,
char **typeName);
Purpose
Gets a property type name. This function returns the name associated with the property type.
Parameters
Input

propertyType

Output typeName

PropTypeHandleX Handle to property type for which the
name is to be obtained. This value must
either be one of the predefined property
types or be a value returned by
CreateXPropType.
character pointer
(passed by reference)

The property type name.

Warning: The typeName pointer points to memory allocated by CreateXPropType. You
must not attempt to free this pointer or to change its contents.
Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to the name parameter.

InvalidPropTypeXErr

-5 The propertyType argument is not a valid property type.
This value must either be one of the predefined property
types or be a value returned by CreateXPropType.

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See Also
CreateXPropType

GetXPropTypeSize
PropLibXErrType status = GetXPropTypeSize (PropTypeHandleX propertyType,
unsigned int *size);
Purpose
Gets a property type size. This function returns the size associated with the property type. The
size is the number of bytes in a single property item.
Parameters
Input

propertyType

Output size

PropTypeHandleX Handle to property type for which the size
is to be obtained. This value must either
be one of the predefined property types or
be a value returned by
CreateXPropType.
unsigned integer
(passed by reference)

The size associated with the property type.
The size is the number of bytes in a single
property item.

Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to the size parameter.

InvalidPropTypeXErr

-5 The propertyType argument is not a valid property type.
This value must either be one of the predefined property
types or be a value returned by CreateXPropType.

See Also
CreateXPropType

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GetXPropTypeUnit
PropLibXErrType status = GetXPropTypeUnit (PropTypeHandleX propertyType,
unsigned int *unit);
Purpose
Get a property type unit.
This function returns the unit associated with the property type. The unit is the number of bytes
(1, 2, or 4) in the basic objects that make up a property item.
Parameters
Input

propertyType

Output unit

PropTypeHandleX

Handle to property type for which the unit is
to be obtained. This value must either be one
of the predefined property types or be a value
returned by CreateXPropType.

unsigned integer
(passed by
reference)

The unit associated with the property type.
The unit is the number of bytes (1, 2 or 4) in
the basic objects that make up a property item.

Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0

The function was successful.

InvalidParamXErr

-1

NULL was passed to the unit parameter.

InvalidPropTypeXErr -5

The propertyType argument is not a valid property type.
This value must either be one of the predefined property
types or be a value returned by CreateXPropType.

See Also
CreateXPropType

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GetXWindowPropertyItem
PropLibXErrType status = GetXWindowPropertyItem (DisplayPtrX display,
WindowX window,
PropertyHandleX property,
void *propertyItem);
Purpose
Get a single property item from a window.
This function obtains the value of the specified property on the window and copies a single item
into the supplied buffer. When there are more than one item in the property value, this function
obtains only the first one. This function does not change the property value.
If the property does not exist on the window, this function reports the
MissingPropertyXErr error.
Use the function GetXWindowPropertyValue to get multiple property items.
Parameters
Input

display

DisplayPtrX

A pointer to the display of the X server to
which the window belongs.

window

WindowX

The window from which the property
item is to be obtained.

property

PropertyHandleX

Handle of the property to be obtained.
This value must have been obtained with
CreateXProperty.

generic pointer

Property item obtained from window.

Output propertyItem

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Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0

The function was successful.

InvalidParamXErr

-1

NULL was passed to one or more parameters.

InvalidDisplayXErr

-2

The display argument is not a valid display. This
argument must either be the predefined value
CVIXDisplay or be the value returned by
ConnectToXDisplay.

InvalidWindowXErr

-3

The window argument is not a valid window.

InvalidPropertyXErr

-4

The property argument is not a valid property handle.
This argument must be the value returned by
CreateXProperty.

TypeMismatchXErr

-12 The actual X type of the property value on the window
does not match the type specified for property.

UnitMismatchXErr

-13 The actual X format of the property value on the window
does not match the unit specified for property.

SizeMismatchXErr

-15 The number of bytes in the property value is not a multiple
of the size specified for property.

MissingPropertyXErr

-18 The property does not exist on the window.

InsuffMemXErr

-19 There is insufficient memory to perform the operation.

GeneralXErr

-20 An Xlib function failed for some unknown reason.

BrokenConnectionXErr -21 The connection to the X server was broken. This occurs if
the remote server terminated.
Parameter Discussion
display must either be the predefined value CVIXDisplay or be the value returned by
ConnectToXDisplay. Use CVIXDisplay if the window is on the same display used by
LabWindows/CVI.
For the window parameter, use CVIXRootWindow to access the default root window of the
display used by LabWindows/CVI. Use CVIXHiddenWindow to access the hidden window
associated with your application.
propertyItem must point to an object of the same size as the property item. You can get the size
of the property item by calling the function GetXPropertySize.

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See Also
Refer to the Xlib Programming Manual or to Xlib—C Language X Interface, MIT X Consortium
Standard for more information about the XGetWindowProperty function.

GetXWindowPropertyValue
PropLibXErrType status = GetXWindowPropertyValue (DisplayPtrX display,
WindowX window, PropertyHandleX property,
unsigned int index, unsigned int numberofItemsRequested,
int delete, unsigned int *numberofItemsReturned,
unsigned int *numberOfItemsRemaining,
void *propertyValue);
Purpose
Get the value of a property on a window.
This function obtains the value of the specified property on the window and copies it into the
supplied buffer.
Note: If the property does not exist on the window, this function does NOT report an error.
Instead, the number of items returned is set to 0.

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Parameters
Input

display

DisplayPtrX

A pointer to the display of the
X server to which the window
belongs.

window

WindowX

The window from which the
property value is to be obtained.

property

PropertyHandleX Handle of the property to be
obtained. This value must have
been obtained with
CreateXProperty.

index

unsigned integer

Index into the property value
where reading is to begin.
Specify the number of property
items to skip from the start of the
property value.

numberofItemsRequested

unsigned integer

Number of property items to
obtain from the window.

delete

integer

Flag indicating whether to delete
the property value from the
window after it is obtained.
Specify 1 to delete the portion of
the property value that was
obtained. Specify 0 to leave the
property value as it is.

Output numberofItemsReturned

unsigned integer
Number of property items that
(passed by reference) were obtained from the window.

Number of property items on the
numberOfItemsRemaining unsigned integer
(passed by reference) window that were neither skipped
nor obtained. Pass NULL for
this parameter if you do not need
this information.
propertyValue

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generic pointer

9-23

Property value obtained from
window. This parameter must
point to an array of size N by M
bytes, where N is the size of the
property item, and M is the
number of items requested.

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Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0

The function was successful.

InvalidParamXErr

-1

NULL was passed to one or more parameters.

InvalidDisplayXErr

-2

The display argument is not a valid display. This
argument must either be the predefined value
CVIXDisplay or be the value returned by
ConnectToXDisplay.

InvalidWindowXErr

-3

The window argument is not a valid window.

InvalidPropertyError -4

The property argument is not a valid property handle.
This argument must be the value returned by
CreateXProperty.

TypeMismatchXErr

-12 The actual X type of the property value on the window
does not match the type specified for property.

UnitMismatchXErr

-13 The actual X format of the property value on the window
does not match the unit specified for property.

InvalidIndexXErr

-14 The index specified is larger than the actual number of
property items on the window.

SizeMismatchXErr

-15 The number of bytes in the property value is not a multiple
of the size specified for property.

InsuffMemXErr

-19 There is insufficient memory to perform the operation.

GeneralXErr

-20 An Xlib function failed for some unknown reason.

BrokenConnectionXErr -21 The connection to the X server was broken. This occurs if
the remote server terminated.
Parameter Discussion
display must either be the predefined value CVIXDisplay or be the value returned by
ConnectToXDisplay. Use CVIXDisplay if the window is on the same display used by
LabWindows/CVI.
For the window parameter, use CVIXRootWindow to access the default root window of the
display used by LabWindows/CVI. Use CVIXHiddenWindow to access the hidden window
associated with your application.
numberofItemsReturned will be less than or equal to the number of property items requested.
If the property does not exist on the window or there is no property value, this value will be 0.
You must check this value to determine if any property items were read.

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See Also
Refer to the Xlib Programming Manual or to Xlib—C Language X Interface, MIT X Consortium
Standard for more information about the XGetWindowProperty function.

InstallXPropertyCallback
PropLibXErrType status = InstallXPropertyCallback (DisplayPtrX display,
const WindowX windowList[],
unsigned int numberofWindows,
const PropertyHandleX propertyList[], unsigned
int numberofProperties,
const void *callbackData, PropertyCallbackTypeX
*callbackFunction);
Purpose
Install a property callback function.
The specified function is called whenever one of the specified properties on one of the specified
windows changes in any way. If more than one function is installed for the same property, the
functions are called in the reverse order in which they were installed.
If the function is already installed as a callback function, the list of windows and properties that
are associated with that function are replaced with those specified by the new installation.
Parameters
DisplayPtrX

A pointer to the display of the
X server to which the window
belongs.

windowList

const WindowX []

An array of windows on which
the properties may exist.

numberofWindows

unsigned integer

Number of windows in the
Window List. This value must
be greater than 0.

propertyList

const
PropertyCallbackTypeX []

An array of handles to
properties for which the
callback is called.

Input display

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Parameters (Continued)
numberofProperties

unsigned integer

Number of properties in the
Property List.

callbackData

generic pointer

Pointer to data to be passed to
the callback function. This
value is passed to the callback
function as the userData
parameter.

callbackFunction

PropertyCallbackTypeX *

Pointer to the function to be
called when the properties
change.

Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
Table 9-4. Status Values for InstallXPropertyCallback
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to one or more parameters. The
number of windows argument is 0.

InvalidDisplayXErr

-2 The display argument is not a valid display. This
argument must either be the predefined value
CVIXDisplay or be the value returned by
ConnectToXDisplay.

InvalidWindowXErr

-3 One or more of the windows in the windowList argument
are not valid.

InvalidPropertyXErr

-4 One or more of the property handles in the propertyList
argument are not valid. These properties must be values
returned by CreateXProperty.

InsuffMemXErr

-19 There is insufficient memory to perform the operation.

BrokenConnectionXErr -21 The connection to the X server was broken. This occurs if
the remote server terminated.
Parameter Discussion
display must either be the predefined value CVIXDisplay or be the value returned by
ConnectToXDisplay. Use CVIXDisplay if the window is on the same display used by
LabWindows/CVI.
To specify a single window, named win, pass the expression &win for the windowList
parameter and pass 1 for the numberOfWindows. Use &CVIXRootWindow to access the

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default root window of the display used by LabWindows/CVI. Use &CVIXHiddenWindow to
specify the hidden window associated with your application.
If numberofProperties is 0 or the propertyList value is ANY_X_PROPERTY, the callback
function is called whenever any property changes on any of the windows in the windowList.
The values in the propertyList array must have been obtained with CreateXProperty.
To specify a single property, named prop, pass the expression &prop for this parameter and
pass 1 for the numberOfProperties. If this value is ANY_X_PROPERTY or the
numberOfProperties is 0, the callback function is called whenever any property changes on any
of the windows in the windowList.
See Also
Refer to the Xlib Programming Manual or to Xlib—C Language X Interface, MIT X Consortium
Standard for more information about the PropertyNotify event.

PutXWindowPropertyItem
PropLibXErrType status = PutXWindowPropertyItem (DisplayPtrX display,
WindowX window, PropertyHandleX property,
void *propertyItem);
Purpose
This function stores the supplied property item with the specified property on the window. Any
existing property value is replaced by this value.
To store multiple property items, use the function PutXWindowPropertyValue.
Parameters
Input

display

DisplayPtrX

A pointer to the display of the X server to
which the window belongs.

window

WindowX

The window on which the property item is to
be stored.

property

PropertyHandleX Handle of the property to be stored. This
value must have been obtained with
CreateXProperty.

propertyItem generic pointer

© National Instruments Corporation

Property item to be stored on the window.
This parameter must point to an object of the
same size as a property item. You can get
the property item size by calling the function
GetXPropertySize.

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Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to one or more parameters.

InvalidDisplayXErr

-2 The display argument is not a valid display. This
argument must either be the predefined value
CVIXDisplay or be the value returned by
ConnectToXDisplay.

InvalidWindowXErr

-3 The window argument is not a valid window.

InvalidPropertyXErr

-4 The property argument is not a valid property handle.
This argument must be the value returned by
CreateXProperty.

InsuffMemXErr

-19 There is insufficient memory to perform the operation.

GeneralXErr

-20 An Xlib function failed for some unknown reason.

BrokenConnectionXErr -21 The connection to the X server was broken. This occurs if
the remote server terminated.
Parameter Discussion
display must either be the predefined value CVIXDisplay or be the value returned by
ConnectToXDisplay. Use CVIXDisplay if the window is on the same display used by
LabWindows/CVI.
For the window parameter, use CVIXRootWindow to access the default root window of the
display used by LabWindows/CVI. Use CVIXHiddenWindow to access the hidden window
associated with your application.
See Also
Refer to the Xlib Programming Manual or to Xlib—C Language X Interface, MIT X Consortium
Standard for more information about the XChangeProperty function.
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PutXWindowPropertyValue
PropLibXErrType status = PutXWindowPropertyValue (DisplayPtrX display,
WindowX window, PropertyHandleX property,
unsigned int numberofItems, int mode,
void *propertyValue);
Purpose
This function stores the supplied value with the property on the window.
To store a single property item, you can use the function PutXWindowPropertyItem.
Parameters
Input

display

DisplayPtrX

A pointer to the display of the X server to
which the window belongs.

window

WindowX

The window on which the property value is to
be stored.

property

PropertyHandleX

Handle of the property to be stored. This
value must have been obtained with
CreateXProperty.

numberofItems

unsigned integer

Number of property items to store on the
window.

mode

integer

Mode in which property value is stored.

propertyValue

generic pointer

Property value to be stored on the window.
This parameter must be an array of size N by M
bytes, where N is the size of a property item,
and M is the number of items to be written.

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Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to one or more parameters. mode is not
ReplaceXPropMode, PrependXPropMode or
AppendXPropMode.

InvalidDisplayXErr

-2 The display argument is not a valid display. This
argument must either be the predefined value
CVIXDisplay or be the value returned by
ConnectToXDisplay.

InvalidWindowXErr

-3 The window argument is not a valid window.

InvalidPropertyXErr

-4 The property argument is not a valid property handle.
This argument must be the value returned by
CreateXProperty.

TypeMismatchXErr

-12 The actual X type of the property value on the window
does not match the type specified for property. This can
only occur if you set mode to append or prepend.

UnitMismatchXErr

-13 The actual X format of the property value on the window
does not match the unit specified for property. This can
only occur if you set mode to append or prepend.

OverflowXErr

-16 Arithmetic overflow occurred with calculations involving
the property item sizes and the number of items specified.

InsuffMemXErr

-19 There is insufficient memory to perform the operation.

GeneralXErr

-20 An Xlib function failed for some unknown reason.

BrokenConnectionXErr -21 The connection to the X server was broken. This occurs if
the remote server terminated.
Parameter Discussion
display must either be the predefined value CVIXDisplay or be the value returned by
ConnectToXDisplay. Use CVIXDisplay if the window is on the same display used by
LabWindows/CVI.
For the window parameter, use CVIXRootWindow to access the default root window of the
display used by LabWindows/CVI. Use CVIXHiddenWindow to access the hidden window
associated with your application.

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The following values are valid for the mode parameter:
ReplaceXPropMode—Replace the existing property value with the new value.
PrependXPropMode—Add the new property value to the beginning of the existing value.
AppendXPropMode—Add the new property value to the end of the existing value.
See Also
Refer to the Xlib Programming Manual or to Xlib—C Language X Interface, MIT X Consortium
Standard for more information about the XChangeProperty function.

RemoveXWindowProperty
PropLibXErrType status = RemoveXWindowProperty (DisplayPtrX display,
WindowX window,
PropertyHandleX property);
Purpose
Remove the property from a window.
This function deletes the property value and removes the property from the window.
Parameters
Input

display

DisplayPtrX

A pointer to the display of the X server to
which the window belongs.

window

WindowX

The window from which the property is
to be removed.

property

PropertyHandleX Handle of the property to be removed.
This value must have been obtained with
CreateXProperty.

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Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr

0 The function was successful.

InvalidParamXErr

-1 NULL was passed to one or more parameters.

InvalidDisplayXErr

-2 The display argument is not a valid display. This
argument must either be the predefined value
CVIXDisplay or be the value returned by
ConnectToXDisplay.

InvalidWindowXErr

-3 The window argument is not a valid window.

InvalidPropertyXErr

-4 The property argument is not a valid property handle.
This argument must be the value returned by
CreateXProperty.

InsuffMemXErr

-19 There is insufficient memory to perform the operation.

BrokenConnectionXErr -21 The connection to the X server was broken. This occurs if
the remote server terminated.
Parameter Discussion
display must either be the predefined value CVIXDisplay or be the value returned by
ConnectToXDisplay. Use CVIXDisplay if the window is on the same display used by
LabWindows/CVI.
For the window parameter, use CVIXRootWindow to access the default root window of the
display used by LabWindows/CVI. Use CVIXHiddenWindow to access the hidden window
associated with your application.
See Also
Refer to the Xlib Programming Manual or to Xlib—C Language X Interface, MIT X Consortium
Standard for more information about the XDeleteProperty function.

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UninstallXPropertyCallback
PropLibXErrType status = UninstallXPropertyCallback
(PropertyCallbackTypeX *callbackFunction);
Purpose
Uninstall a property callback function.
After a callback function is uninstalled, it is no longer called when properties change. All
property callback functions are automatically uninstalled when the program terminates.
Note: Although you cannot selectively uninstall certain properties or windows associated
with a callback function, you can reinstall a callback function with a new set of
windows and properties using InstallXPropertyCallback.
Parameters
Input callbackFunction PropertyCallbackTypeX* The function that was installed with
InstallXPropertyCallback.
Return Values
The return value indicates the success or failure status of the function call. A negative value
indicates an error. The following table shows status values.
NoXErr
InvalidCallbackXErr

0 The function was successful.
-17 The function specified is not installed as a callback.

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Chapter 10
Easy I/O for DAQ Library
This chapter describes the functions in the Easy I/O for DAQ Library. The Easy I/O for DAQ
Library Function Overview section contains general information about the functions, and
guidelines and restrictions you should know when using the Easy I/O for DAQ Library. The Easy
I/O for DAQ Library Function Reference section contains an alphabetical list of function
descriptions.

Easy I/O for DAQ Library Function Overview
The functions in the Easy I/O for DAQ Library make it easier to write simple DAQ programs
than if you use the Data Acquisition Library.
This library implements a subset of the functionality of the Data Acquisition Library, but it does
not use the same functions as the Data Acquisition Library. Read the advantages and limitations
listed here to see if the Easy I/O for DAQ Library is appropriate for your application.
You must have NI-DAQ for PC Compatibles installed to use the Easy I/O for DAQ library. The
Easy I/O for DAQ library has been tested using version 4.6.1 and later of NI-DAQ. It has not
been tested using previous versions of NI-DAQ.
The sample programs for the Easy I/O for DAQ library are located in the
cvi\samples\easyio directory. These sample programs are discussed in the EASYIO
section of cvi\samples.doc.
Note: It is recommended that you do not mix calls to the Data Acquisition Library with
similar types of calls to the Easy I/O for DAQ Library in the same application. For
example, do not mix analog input calls to the Data Acquisition Library with analog
input calls to the Easy I/O for DAQ Library in the same program.

Advantages of Using the Easy I/O for DAQ Library
If you want to scan multiple analog input channels on an MIO board using the Data Acquisition
Library, you have to programmatically build a channel list and a gain list before calling
SCAN_Op.
The Easy I/O for DAQ functions accept a channel string and upper and lower input limit
parameters so that you can easily perform a scan in one step.
In the Data Acquisition Library you may have to use Lab_ISCAN_Op, or SCAN_Op, or
MDAQ_Start depending on which DAQ device you are using. Also, if you are using SCXI,
there are a number of SCXI specific functions that must be called prior to actually acquiring data.

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Chapter 10

The Easy I/O for DAQ functions are device independent which means that you can use the same
function on a Lab series board, an MIO board, an EISA-A2000 or SCXI module.

Limitations of Using the Easy I/O for DAQ Library
The Easy I/O for DAQ Library currently only works with Analog I/O, Counter/Timers, and
simple Digital I/O.
The Easy I/O for DAQ Library does not currently work with multirate scanning.

Easy I/O for DAQ Library Function Panels
The Easy I/O for DAQ Library function panels are grouped in a tree structure according to the
types of operations performed. The Easy I/O for DAQ Library function tree is in Table 10-1.
The first- and second-level bold headings in the function tree are names of the function classes.
Function classes are groups of related function panels. The third-level headings in plain text are
the names of individual function panels. Each Easy I/O for DAQ function panel generates a
function call. The actual function names are in bold italics in columns to the right.
Table 10-1. Easy I/O for DAQ Function Tree
Analog Input
AI Sample Channel
AI Sample Channels
AI Acquire Waveform(s)
AI Acq. Triggered Waveform(s)
Asynchronous Acquisition
AI Start Acquisition
AI Check Acquisition
AI Read Acquisition
AI Clear Acquisition
Plot Last Waveform(s) to Popup
Analog Output
AO Update Channel
AO Update Channels
AO Generate Waveform(s)
AO Check Waveform(s)
AO Clear Waveform(s)

AISampleChannel
AISampleChannels
AIAcquireWaveforms
AIAcquireTriggeredWaveforms
AIStartAcquisition
AICheckAcquisition
AIReadAcquisition
AIClearAcquisition
PlotLastAIWaveformsPopup
AOUpdateChannel
AOUpdateChannels
AOGenerateWaveforms
AOCheckWaveforms
AOClearWaveforms
(continues)

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Table 10-1. Easy I/O for DAQ Function Tree (Continued)
Digital Input/Output
Read From Digital Line
Read From Digital Port
Write To Digital Line
Write To Digital Port
Counter/Timer
Counter Measure Frequency
Counter Event or Time Configure
Continuous Pulse Gen Configure
Delayed Pulse Gen Configure
Frequency Divider Configure
Pulse Width or Period Meas Conf
Counter Start
Counter Read
Counter Stop
I Counter Control
Miscellaneous
Get DAQ Error Description
Get Number Of Channels
Get Channel Indices
Get Channel Name From Index
Get AI Limits of Channel
Group By Channel
Set Multitasking Mode

ReadFromDigitalLine
ReadFromDigitalPort
WriteToDigitalLine
WriteToDigitalPort
CounterMeasureFrequency
CounterEventOrTimeConfig
ContinuousPulseGenConfig
DelayedPulseGenConfig
FrequencyDividerConfig
PulseWidthOrPeriodMeasConfig
CounterStart
CounterRead
CounterStop
ICounterControl
GetDAQErrorString
GetNumChannels
GetChannelIndices
GetChannelNameFromIndex
GetAILimitsOfChannel
GroupByChannel
SetEasyIOMultitaskingMode

•

The Analog Input function class contains all of the functions that perform A/D conversions.

•

The Asynchronous Acquisition function class contains all of the functions that perform
asynchronous (background) A/D conversions.

•

The Analog Output function class contains all of the functions that perform D/A
conversions.

•

The Digital Input/Output function class contains all of the functions that perform digital
input and output operations.

•

The Counter/Timer function class contains all of the functions that perform counting and
timing operations.

•

The Miscellaneous function class contains functions that do not fit into the other categories,
but are useful when writing programs using the Easy I/O for DAQ Library.

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Chapter 10

Device Numbers
The first parameter to most of the Easy I/O for DAQ functions is the device number of the DAQ
device you want to use for the given operation. After you have followed the installation and
configuration instructions in Chapter 1, Introduction to NI-DAQ, of the NI-DAQ User Manual
for PC Compatibles, the configuration utility displays the device number for each device you
have installed in the system. You can use the configuration utility to verify your device numbers.
You can use multiple DAQ devices in one application; to do so, simply pass the appropriate
device number to each function.

Channel String for Analog Input Functions
The second parameter to most of the analog input functions is the channel string containing the
analog input channels that are to be sampled.
Refer to Chapter 2, Hardware Overview, in your NI-DAQ User Manual for PC Compatibles to
determine exactly what channels are valid for your hardware.
The syntax for the Channel String is as follows:
•

If you are using an MIO board, NEC-AI-16E-4, or NEC-AI-16XE-50, list the channels in
the order in which they are to be read, as in the following example:
"0,2,5"
"0:3"

•

/* reads channels 0, 2, and 5 in that order */
/* reads channels 0 through 3 inclusive
*/

If you are using AMUX-64T boards:
You can address AMUX-64T channels when you attach one, two, or four AMUX-64T boards
to a plug-in data acquisition board.
Refer to Chapter 2, Hardware Overview, in your NI-DAQ User Manual for PC Compatibles
to determine how AMUX-64T channels are multiplexed onto onboard channels.
The onboard channel to which each block of four, eight, or 16 AMUX-64T channels are
multiplexed and the scanning order of the AMUX-64T channels are fixed. To specify a range
of AMUX-64T channels, therefore, you enter in the channel list the onboard channel into
which the range is multiplexed. For example, if you have one AMUX-64T:
"0"

/* reads channels 0 through 3 on each AMUX-64T board in that order */

To sample a single AMUX-64T channel, you must also specify the number of the AMUX64T board, as in the following example:
"AM1!3" /* samples channel 3 on AMUX-64T board 1
"AM4!8" /* samples channel 8 on AMUX-64T board 4

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*/

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•

If you are using a Lab-PC+, DAQCard-500/700/1200, DAQPad-1200, PC-LPM-16:
These devices can only sample input channels in descending order, and you must end with
channel 0 ("3:0"). If you are using a Lab-PC+ or 1200 product in differential mode, you
must use even-numbered channels ("6,4,2,0").

•

If you are using a DAQPad-MIO-16XE-50:
You can read the value of the cold junction compensation temperature sensor using the
following string as the channel:
"cjtemp"

•

If you are using SCXI:
You can address SCXI channels when you attach one or more SCXI chassis to a plug-in data
acquisition board. If you operate a module in parallel mode, you can select a SCXI channel
either by specifying the corresponding onboard channels or by using the SCXI channel
syntax described below. If you operate the modules in multiplexed mode, you must use the
SCXI channel syntax.

The SCXI channel syntax is as follows:
•
•

"OB1!SCx!MDy!a" /* channel a on the module in slot y of the chassis with
ID x is multiplexed into onboard channel 1 */
"OB0!SCx!MDy!a:b" /* channels a through b inclusive on the module in slot
y of the chassis with ID x is multiplexed into onboard channel 0 */

SCXI channel ranges cannot cross module boundaries. SCXI channel ranges must always
increase in channel number.
The following examples of the SCXI channel syntax introduce the special SCXI channels:
•
•
•
•

•

"OB0!SCx!MDy!MTEMP"
/* The temperature sensor configured in MTEMP mode
on the multiplexed module in slot y of the chassis with ID x. */
"OB1!SCx!MDy!DTEMP"
/* The temperature sensor configured in DTEMP mode
on the parallel module in slot y of the chassis with ID x. */
"OB0!SCx!MDy!CALGND" /* (SCXI-1100 and SCXI-1122 only) The grounded
amplifier of the module in slot y of the chassis with ID x. */
"OB0!SCx!MDy!SHUNT0" /* (SCXI-1121, SCXI-1122 and SCXI-1321 only) Channel
0 of the module in slot y of the chassis with ID x, with the shunt resistor
applied. */
"OB0!SCx!MDy!SHUNT0:3" /* (SCXI-1121, SCXI-1122 and SCXI-1321 only) Channel
0 through 3 of the module in slot y of the chassis with ID x, with the
shunt resistors applied at each channel. */

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Command Strings
You can use command strings within the Channel String to set per-channel limits and an
interchannel sample rate. For example,
"cmd hi 10.0 low -10.0; 7:4; cmd hi 5.0 low -5.0; 3:0"

specifies that channels 7 through 4 should be scanned with limits of +/- 10.0 volts and
channels 3 through 0 should be scanned with limits of +/- 5.0 volts. As you view the
Channel String from left to right, when a high/low limit command is encountered, those limits
are assigned to the following channels until the next high/low limit command is encountered.
The High Limit and Low Limit parameters to AISampleChannels are the initial high/low
limits. These parameters can be thought of as the left-most high/low limit command.
The following Channel String,
"cmd interChannelRate 1000.0; 0:3"

specifies that channels 0 through 3 should be sampled at 1000.0 Hz, in other words, there should
be 1/1000.0 = 1ms of delay between each channel. If you do not set an interchannel sample rate,
the channels are sampled as fast as possible for your hardware to achieve pseudo simultaneous
scanning.
The syntax for the command string can be described using the following guide:
•

items enclosed in [] are optional

•

 is an integer or real number

•

 is a line-feed character

•

;| means you may use either ; or  to separate command strings from channel
strings

•

! may be used as an optional command separator

•

spaces are optional

The syntax for the initial command string that appears before any channels are specified is:
"cmd [interChannelRate [!]] [hi  [!]low [!]];|"

The syntax for command strings that appear after any channels are specified is:
";| cmd hi [!] low [!] ;|"

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Channel String for Analog Output Functions
The second parameter to most of the analog output functions is the channel string containing the
analog output channels that are to be driven.
Refer to the chapter specific to your DAQ device in the DAQ Hardware Overview Guide to
determine what channels are valid for your hardware. The document is an Adobe Acrobat file,
daqhwov.pdf, that you can view on screen and also print. daqhwov.pdf is part of a set of
.pdf files that come with every DAQ device sold by National Instruments.
The syntax for the Channel String is as follows:
•

If you are using a DAQ device without SCXI, list the channels to be driven, as in the
following example:
"0,2,5"
"0:3"

•

/* drives channels 0, 2, and 5 */
/* drives channels 0 through 3 inclusive */

If you are using SCXI, you can address SCXI channels when you attach one or more SCXI
chassis to a plug-in data acquisition board.

The SCXI channel syntax is as follows:
"SCx!MDy!a"
"SCx!MDy!a:b"

/* channel a on the module in slot y of the chassis with ID x */
/* channels a through b inclusive on the module in slot y of
the chassis with ID x */

SCXI channel ranges cannot cross module boundaries. SCXI channel ranges must always
increase in channel number.

Valid Counters for the Counter/Timer Functions
The second parameter to most of the counter/timer functions is the counter used for the
operation. The valid counters you can use depends on your hardware as shown in Table 10-2.
Table 10-2. Valid Counters
Device Type

Valid Counters

DAQ-STC Devices

0 and 1

Am9513 MIO boards

1, 2, and 5

PC-TIO-10

1 through 10

EISA-A2000

2

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Easy I/O for DAQ Function Reference
This section describes each function in the Easy I/O for DAQ Library. The function descriptions
are arranged alphabetically.

AIAcquireTriggeredWaveforms
short error = AIAcquireTriggeredWaveforms (short device, char channelString[],
long numberOfScans,
double scansPerSecond,
double highLimitVolts,
double lowLimitVolts,
double *actualScanRate,
unsigned short triggerType,
unsigned short edgeSlope,
double triggerLevelV,
char triggerSource[],
long pretriggerScans,
double timeLimitsec,
short fillMode, double waveforms[]);
Purpose
This function performs a timed acquisition of voltage data from the analog channels specified in
the channelString. The acquisition does not start until the trigger conditions are satisfied.
If you have an E Series DAQ device, you can select Equivalent Time Sampling for the Trigger
Type to sample repetitive waveforms at up to 20 MHz. See the help for the Trigger Type
parameter for details.

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Parameters
Input

Output

device

short integer

Assigned by configuration utility.

channelString

string

Analog input channels that are to be sampled.

numberOfScans

long integer

Number of scans to be acquired complete. One
scan involves sampling every channel in the
channelString once.

scansPerSecond

double

Number of scans performed per second. Any
particular channel to be scanned at this rate.

highLimitVolts

double

Maximum voltage to be measured.

lowLimitVolts

double

Minimum voltage to be measured.

triggerType

unsigned
short integer

The trigger type.

edgeSlope

unsigned
short integer

The edge/slope condition for triggering.

triggerLevelV

double

Voltage at which the trigger is to occur.

triggerSource

string

Specifies which channel is the trigger source.

pretriggerScans

long integer

Specifies the number of scans to retrieve before
the trigger point.

timeLimitsec

double

The maximum length of time in seconds to wait
for the data.

fillMode

short integer

Specifies whether the waveforms array are in
GROUP_BY_CHANNEL or GROUP_BY_SCAN
mode.

actualScanRate

double

The actual scan rate. The actual scan rate may
differ slightly from the scan rate you specified,
given the limitations of your particular DAQ
device.

waveforms

double array

Array containing the voltages acquired on the
channels specified in the channelString.

short integer

Refer to error codes in Table 10-5.

Return Value
error

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Parameter Discussion
channelString is the analog input channels that are to be sampled. Refer to the Channel String
for Analog Input Functions subsection of the Easy I/O for DAQ Library Function Overview
section of this chapter for the syntax of this string.
triggerType is the trigger type. The trigger types are:
Hardware Analog Trigger:
Digital Trigger A:
Digital Triggers A & B:
Scan Clock Gating:
Software Analog Trigger:
Equivalent Time Sampling

HW_ANALOG_TRIGGER
DIGITAL_TRIGGER_A
DIGITAL_TRIGGER_AB
SCAN_CLOCK_GATING
SW_ANALOG_TRIGGER
ETS_TRIGGER

•

If you choose Hardware or Software Analog Trigger, data is retrieved after the analog
triggering parameters have been satisfied. Be sure that the Trigger Source is one of the
channels listed in the channel string. Hardware triggering is more accurate than software
triggering, but it is not available on all boards.

•

If you choose Digital Trigger A:
– If pretriggerScans is 0, the trigger starts the acquisition. For the MIO-16, connect the
digital trigger signal to the START TRIG input.
– If pretriggerScans is greater than 0, the trigger stops the acquisition after all posttrigger
data is acquired. For the MIO-16, connect the digital trigger signal to the STOP TRIG
input.

•

If you choose Digital Trigger A & B:
– pretriggerScans must be greater than 0. A digital trigger starts the acquisition and a
digital trigger stops the acquisition after all posttrigger data is acquired.
– For the MIO-16, the START TRIG input starts the acquisition and the STOP TRIG input
stops the acquisition.

•

If you choose Scan Clock Gating, an external signal gates the scan clock on and off. If the
scan clock gate becomes FALSE, the current scan completes, and the scan clock ceases
operation. When the scan clock gate becomes TRUE, the scan clock immediately begins
operation again.

•

If you choose Equivalent Time Sampling: This is a mode in which the Equivalent Time
Sampling technique is used on an E Series DAQ device to achieve an effective acquisition
rate of up to 20 MHz.
– The signal that is being measured must be a periodic waveform.
– The trigger conditions must be satisfied or this function times out.
– Equivalent Time Sampling is the process of taking A/D conversions from a periodic
waveform at special points in time such that when the A/D conversions are placed sideby-side, they represent the original waveform as if it had been sampled at a high
frequency.

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For example, if the A/D conversions (represented by x's) on the waveform shown below are
placed side-by-side, they represent one cycle of the waveform.
_
_
_
x
_
_
_
/ \
/ \
x \
/ \
/ x
/ \
/ \
/
\
x
\
/
\
/
\
/
\
/
x
/
\
x
\_/
\_/
\_/
\_/
\_/
\_/
x_/
x
x x
x
x
x
x

Equivalent Time Sampling is accomplished in this function as follows:
1. Set a hardware analog trigger condition for measuring your waveform using the Edge/Slope,
Trigger Level, and Trigger Source parameters of this function.
2. Whenever a hardware analog trigger occurs, the internal ATCOUT signal is strobed.
3. The ATCOUT signal is internally routed to the gate of GPCTR0, which is configured to
generate a pulse each time it receives a rising edge at it's gate input.
4. The output of GPCTR0 is internally routed to the data acquisition sample clock to control the
A/D conversion rate.
5. The very high effective scan rate is achieved through a pre-pulse delay that is programmed
into GPCTR0. This delay automatically increments before each GPCTR0 pulse so that the
A/D conversions occur at slightly larger intervals from the trigger condition as trigger
conditions occur over time.
6. Because the waveform being measured is periodic, A/D conversions that are at particular
intervals from trigger conditions over time can look the same as A/D conversions at
particular intervals from one unique trigger point in time.
In the following figure:
tn => the nth trigger condition
dn => delay between the nth trigger and the nth conversion
x => an A/D conversion
- - - => the trigger level
_
_
_
x
_
_
_
/ \
/ \
x \
/ \
/ x
/ \
/ \
/
\
x
\
/
\
/
\
/
\
/
x
/
\
x- - -\-/- - -\-/- - -\-/- - -\-/- - -\-/- - -\-/- - -x-/________________________________________________________
t0
t1
t2
t3
t4
t5
t6
||
|-|
|--|
|---|
|----| |-----| |------|
d0
d1
d2
d3
d4
d5
d6

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When the A/D conversions are placed side-by-side, they represent the original waveform as if it
had been sampled at a high frequency.
x
x x
x
x
x
x

edgeSlope specifies whether the trigger occurs when the trigger signal voltage is leading
(POSITIVE_SLOPE) or trailing (NEGATIVE_SLOPE).
triggerLevelV the voltage at which the trigger is to occur. triggerLevelV is valid only when the
Trigger Type is hardware or software analog trigger.
triggerSource specifies which channel is the trigger source. triggerSource must be one of the
channels listed in the channelString. Or if you pass "" or NUL, the first channel in the
channelString is used as the triggerSource. triggerSource is valid only when the Trigger Type
is hardware or software analog trigger.
timeLimitsec is the maximum length of time in seconds to wait for the data. If the time you set
expires, the function returns a timeout error (timeOutErr = -10800).
Other Values:
-2.0 disables the time limit.
Warning:

This setting leaves your computer in a suspended state until the trigger
condition occurs.

-1.0 (default) lets the function calculate the timeout based on the acquisition rate and number
of scans requested.
fillMode specifies whether the waveforms array is grouped by channels or grouped by scans.
Consider the following examples:
•

If you scan channels A through C and Number of Scans is 5, then the possible fill modes are:
GROUP_BY_CHANNEL
A1 A2 A3 A4 A5 B1 B2 B3 B4 B5 C1 C2 C3 C4 C5
\----------/
\----------/
\----------/

or
GROUP_BY_SCAN
A1 B1 C1 A2 B2 C2 A3 B3 C3 A4 B4 C4 A5 B5 C5
\----/
\----/
\----/
\----/
\----/

•

If you are to pass the array to a graph, you should acquire the data grouped by channel.

•

If you are to pass the array to a strip chart, you should acquire the data grouped by scan.

•

You can also acquire the data grouped by scan and later reorder it to be grouped by channel
using the GroupByChannel function.

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waveforms is an array containing the voltages acquired on the channels specified in the
channelString. The acquired voltages are placed into the array in the order specified by
fillMode. This array must be declared as large as:
(number of channels) * (numberOfScans)
You can determine the number of channels using the GetNumChannels function.

AIAcquireWaveforms
short error = AIAcquireWaveforms (short device, char channelString[],
long numberOfScans, double scansPerSecond,
double highLimitVolts, double lowLimitVolts,
double *actualScanRate, short fillMode,
double waveforms[]);
Purpose
This function performs a timed acquisition of voltage data from the analog channels specified in
the channelString.
Parameters
Input

Output

device

short
integer

Assigned by configuration utility.

channelString

string

Analog input channels that are to be sampled.

numberOfScans

long
integer

Number of scans to be acquired. One scan involves
sampling every channel in the channelString once.

scansPerSecond

double

Number of scans performed per second. Any
particular channel is scanned at this rate.

highLimitVolts

double

Maximum voltage to be measured.

lowLimitVolts

double

Minimum voltage to be measured.

fillMode

short
integer

Specifies one of the following modes for the
waveforms array: GROUP_BY_CHANNEL or
GROUP_BY_SCAN.

actualScanRate

double

The actual scan rate may differ slightly from the scan
rate you specified, given the limitations of your
particular DAQ device.

waveforms

double
array

Array containing the voltages acquired on the
channels specified in the channelString.

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Return Value
error

short
integer

Refer to error codes in Table 10-5.

Parameter Discussion
channelString is the analog input channels that are to be sampled. Refer to the Channel String
for Analog Input Functions subsection of the Easy I/O for DAQ Library Function Overview
section of this chapter for the syntax of this string.
fillMode specifies whether the waveforms array is grouped by channels or grouped by scans.
Consider the following examples:
•

If you scan channels A through C and Number of Scans is 5, then the possible fill modes are:
GROUP_BY_CHANNEL
A1 A2 A3 A4 A5 B1 B2 B3 B4 B5 C1 C2 C3 C4 C5
\----------/
\----------/
\----------/

or
GROUP_BY_SCAN
A1 B1 C1 A2 B2 C2 A3 B3 C3 A4 B4 C4 A5 B5 C5
\----/
\----/
\----/
\----/
\----/

•

If you are to pass the array to a graph, you should acquire the data grouped by channel.

•

If you are to pass the array to a strip chart, you should acquire the data grouped by scan.

•

You can also acquire the data grouped by scan and later reorder it to be grouped by channel
using the GroupByChannel function.

waveforms is an array containing the voltages acquired on the channels specified in the
channelString. The acquired voltages is placed into the array in the order specified by fillMode.
This array must be declared as large as:
(number of channels) * (numberOfScans)
You can determine number of channels using the function GetNumChannels.

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AICheckAcquisition
short error = AICheckAcquisition (unsigned long taskID,
unsigned long *scanBacklog);
Purpose
This function can be used to determine the backlog of scans that have been acquired into the
circular buffer but have not been read using AIReadAcquisition.
If AIReadAcquisition is called with read mode set to LATEST_MODE, scanBacklog is
reset to zero.
Parameters
Input

taskID

unsigned
long integer

The task ID that was returned from
AIStartAcquisition.

Output

scanBacklog

unsigned
long integer

Returns the backlog of scans that have been acquired
into the circular buffer but have not been read using
AIReadAcquisition.

Return Value
short integer

error

Refer to error codes in Table 10-5.

AIClearAcquisition
short error = AIClearAcquisition (unsigned long taskID);
Purpose
This function clears the current asynchronous acquisition that was started by
AIStartAcquisition.
Parameters
Input

unsigned
long integer

taskID

The task ID that was returned from
AIStartAcquisition.

Return Value
error

short integer

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AIReadAcquisition
short error = AIReadAcquisition (unsigned long taskID, long scanstoRead,
unsigned short readMode,
unsigned long *scanBacklog,
short fillMode, double waveforms[]);
Purpose
This function reads the specified number of scans from the internal circular buffer established by
AIStartAcquisition.
If the specified number of scans is not available in the buffer, the function waits until the scans
are available. You can call AICheckAcquisition before calling AIReadAcquisition to
determine how many scans are available.
Parameters
Input

Output

taskID

unsigned long
integer

The task ID that was returned from
AIStartAcquisition.

scanstoRead

long integer

The number of scans that are read from the internal
circular buffer.

readMode

unsigned
short integer

Specifies whether scans are read from the circular
buffer in CONSECUTIVE_MODE or
LATEST_MODE.

fillMode

short integer

Specifies one of the following modes for the
waveforms array: GROUP_BY_CHANNEL or
GROUP_BY_SCAN.

scanBacklog

unsigned long
integer

Returns the backlog of scans that have been acquired
into the circular buffer but have not been read using
AIReadAcquisition.

waveforms

double array

Array containing the voltages acquired on the
channels specified in the channelString.

short integer

Refer to error codes in Table 10-5.

Return Value
error
Parameter Discussion
readMode specifies whether scans are read from the circular buffer in CONSECUTIVE_MODE or
LATEST_MODE. In CONSECUTIVE_MODE scans are read from the internal circular buffer
starting from the last scan that was read. Using this mode, you are guaranteed that you will not
lose data unless an error occurs. In LATEST_MODE the most recently acquired n scans are read

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from the internal circular buffer, where n is scanstoRead. Calling AIReadAcquisition in
this mode resets the scanBacklog to zero.
scanBacklog returns the backlog of scans that have been acquired into the circular buffer but
have not been read using AIReadAcquisition. If AIReadAcquisition is called in
"latest" read mode, the scan backlog is reset to zero. You can also call AICheckAcquisition
to determine the scan backlog before calling AIReadAcquisition.
waveforms is an array containing the voltages acquired on the channels specified in the
channelString. The acquired voltages are placed into the array in the order specified by
fillMode. This array must be declared as large as:
(number of channels) * (scanstoRead)
You can determine the number of channels by using the function GetNumChannels.

AISampleChannel
short error = AISampleChannel (short device, char singleChannel[],
double highLimitVolts, double lowLimitVolts,
double *voltage);
Purpose
This function acquires a single voltage from a single analog input channel.
Parameters
Input

Output

device

short integer

Assigned by configuration utility.

singleChannel

string

The analog input channel that is to be sampled.

highLimitVolts

double

Maximum voltage to be measured.

lowLimitVolts

double

Minimum voltage to be measured.

voltage

double
(passed by
reference)

Returns the measured voltage.

short integer

Refer to error codes in Table 10-5.

Return Value
error

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Parameter Discussion
singleChannel is the analog input channel that is to be sampled. See the Channel String for
Analog Input Functions subsection of the Easy I/O for DAQ Library Function Overview section
in this chapter for the syntax of this string.

AISampleChannels
short error = AISampleChannels (short device, char channelString[],
double highLimitVolts, double lowLimitVolts,
double voltageArray[]);
Purpose
This function performs a single scan on a set of analog input channels.
Parameters
Input

device

short
integer

Assigned by configuration utility.

channelString

string

Analog input channels that are to be sampled.

highLimitVolts

double

Maximum voltage to be measured.

lowLimitVolts

double

Minimum voltage to be measured.

double
array

Array containing the voltages acquired on the
channels specified in the channelString.

short
integer

Refer to error codes in Table 10-5.

Output voltageArray

Return Value
error

Parameter Discussion
channelString is the analog input channels that are to be sampled. Refer to the Channel String
for Analog Input Functions subsection of the Easy I/O for DAQ Library Function Overview
section of this chapter for the syntax of this string.
voltageArray is an array containing the voltages acquired on the channels specified in the
channelString. The acquired voltages are placed into the array in the order specified in the
channelString. This array must be declared as large as the number of channels specified in the
channelString. You can use the function GetNumChannels to determine the number of
channels.

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AIStartAcquisition
short error = AIStartAcquisition (short device, char channelString[],
int bufferSize, double scansPerSecond,
double highLimitVolts, double lowLimitVolts,
double *actualScanRate,
unsigned long *taskID);
Purpose
This function starts a continuous asynchronous acquisition on the analog input channels specified
in the channelString. Data is acquired into an internal circular buffer. Use
AIReadAcquisition to retrieve scans from the internal buffer.
Parameters
Input

Output

device

short integer

Assigned by configuration utility.

channelString

string

Analog input channels that are to be sampled.

bufferSize

integer

The size of the internal circular buffer in scans.

scansPerSecond

double

Number of scans performed per second. Any
particular channel is scanned at this rate.

highLimitVolts

double

Maximum voltage to be measured.

lowLimitVolts

double

Minimum voltage to be measured.

actualScanRate

double

The actual scan rate may differ slightly from the
scan rate you specified, given the limitations of
your particular DAQ device.

taskID

unsigned
long integer

An identifier for the asynchronous acquisition.

short integer

Refer to error codes in Table 10-5.

Return Value
error
Parameter Discussion
channelString is the analog input channels that are to be sampled. Refer to the Channel String
for Analog Input Functions subsection of the Easy I/O for DAQ Library Function Overview
section of this chapter for the syntax of this string.
taskID is an identifier for the asynchronous acquisition that must be passed to
AICheckAcquisition
AIReadAcquisition
AIClearAcquisition

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Chapter 10

AOClearWaveforms
short error = AOClearWaveforms (unsigned long taskID);
Purpose
This function clears the waveforms generated by AOGenerateWaveforms when you passed 0
for its Iterations parameter.
Parameters
Input

taskID

unsigned
long integer

The task ID that was returned from
AOGenerateWaveforms.

Return Value
error

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AOGenerateWaveforms
short error = AOGenerateWaveforms (short device, char channelString[],
double updatesPerSecond,
int updatesPerChannel, int iterations,
double waveforms[],
unsigned long *taskID);
Purpose
This function generates a timed waveform of voltage data on the analog output channels
specified in the channelString.
Parameters
Input

Output

device

short integer Assigned by configuration utility.

channelString

string

The analog output channels to which the
voltages are applied.

updatesPerSecond

double

The number of updates that are performed per
second. Any particular channel is updated at
this rate.

updatesPerChannel

integer

The number of D/A conversions that compose
a waveform for a particular channel.

iterations

integer

The number of waveform iterations that are
performed before the operation is complete; 0
= continuous.

waveforms

double array The voltages to be applied to the channels
specified in the channelString.

taskID

unsigned
long integer

Returns an identifier for the waveform
generation. If you pass 0 as the iterations
parameter you need to pass the taskID to
AOClearWaveforms to clear the waveform
generation.

Return Value
error

short integer Refer to error codes in Table 10-5.

Parameter Discussion
channelString is the analog output channels to which the voltages are applied. Refer to the
Channel String for Analog Output Functions subsection of the Easy I/O for DAQ Library
Function Overview section of this chapter for the syntax of this string.

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updatesPerChannel is the number of D/A conversions that compose a waveform for a particular
channel. If updatesPerChannel is 10, then each waveform is composed of 10 elements from the
waveforms array.
iterations is the number of waveform iterations that are performed before the operation is
complete. If you pass 0, the waveform(s) are generated continuously and you need to call
AOClearWaveforms to clear waveform generation.
waveforms is the array containing the voltages to be applied to the channels specified in the
channelString. The voltages are applied to the analog output channels in the order specified in
the channelString. For example, if the channelString is
"0:3,5",
the array should contain the voltages in the following order:
waveforms[0]
waveforms[1]
waveforms[2]
waveforms[3]
waveforms[4]
waveforms[5]
waveforms[6]
waveforms[7]
waveforms[8]
waveforms[9]
.
.
.
waveforms[n-5]
waveforms[n-4]
waveforms[n-3]
waveforms[n-2]
waveforms[n-1]

/*
/*
/*
/*
/*
/*
/*
/*
/*
/*

the
the
the
the
the
the
the
the
the
the

1st
1st
1st
1st
1st
2nd
2nd
2nd
2nd
2nd

/*
/*
/*
/*
/*

the
the
the
the
the

last
last
last
last
last

update
update
update
update
update
update
update
update
update
update

update
update
update
update
update

on
on
on
on
on
on
on
on
on
on

on
on
on
on
on

channel
channel
channel
channel
channel
channel
channel
channel
channel
channel

channel
channel
channel
channel
channel

0
1
2
3
5
0
1
2
3
5

*/
*/
*/
*/
*/
*/
*/
*/
*/
*/

0
1
2
3
5

*/
*/
*/
*/
*/

AOUpdateChannel
short error = AOUpdateChannel (short device, char singleChannel[],
double voltage);
Purpose
This function applies a specified voltage to a single analog output channel.

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Parameters
Input

device

short integer

Assigned by configuration utility.

singleChannel

string

The analog output channel to which the voltage are
applied.

voltage

double

The voltage that is applied to the analog output
channel.

short integer

Refer to error codes in Table 10-5.

Return Value
error
Parameter Discussion
singleChannel is the analog output channel to which the voltage are applied. Refer to the
Channel String for Analog Output Functions subsection of the Easy I/O for DAQ Library
Function Overview section of this chapter for the syntax of this string.

AOUpdateChannels
short AOUpdateChannels (short device, char channelString[],
double voltageArray[]);
Purpose
This function applies specified voltages to the analog output channel specified in the
channelString.
Parameters
Input

device

short integer

Assigned by configuration utility.

channelString

string

The analog output channels to which the voltages
are applied.

voltageArray

double array

The voltages that are applied to the specified analog
output channels.

short integer

Refer to error codes in Table 10-5.

Return Value
error

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Parameter Discussion
channelString is the analog output channels to which the voltages are applied. Refer to the
Channel String for Analog Output Functions subsection of the Easy I/O for DAQ Library
Function Overview section of this chapter for the syntax of this string.
voltageArray is the voltages that are applied to the specified analog output channels. This array
should contain the voltages to be applied to the analog output channels in the order that is
specified in the channelString. For example, if the channelString contains:
"0,1,3"

then
voltage[0] = 1.2;
voltage[1] = 2.4;
voltage[2] = 3.6;

/* 1.2 volts applied to channel 0 */
/* 2.4 volts applied to channel 1 */
/* 3.6 volts applied to channel 3 */

ContinuousPulseGenConfig
short error = ContinuousPulseGenConfig (short device, char counter[],
double frequency, double dutyCycle,
unsigned short gateMode,
unsigned short pulsePolarity,
double *actualFrequency,
double *actualDutyCycle,
unsigned long *taskID);
Purpose
Configures a counter to generate a continuous TTL pulse train on its OUT pin.
The signal is created by repeatedly decrementing the counter twice, first for the delay to the pulse
(phase 1), then for the pulse itself (phase 2). The function selects the highest resolution timebase
to achieve the desired characteristics.
You can also call the CounterStart function to gate or trigger the operation with a signal on
the counter's GATE pin.

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Parameters
Input

Output

device

short
integer

Assigned by configuration utility.

counter

string

The counter to be used for the counting operation.

frequency

double

The desired repetition rate of the continuous pulse
train.

dutyCycle

double

The desired ratio of the duration of the pulse phase
(phase 2) to the period (phase 1 + phase 2).

gateMode

unsigned
short
integer

Specifies how the signal on the counter's GATE pin
is used.

pulsePolarity

unsigned
short
integer

The polarity of phase 2 of each cycle.

actualFrequency

double

The achieved frequency based on the resolution and
range of your hardware.

actualDutyCycle

double

The achieved duty cycle based on the resolution and
range of your hardware.

taskID

unsigned
long
integer

The reference number assigned to this operation.
You pass taskID to CounterStart,
CounterRead, and CounterStop.

short
integer

Refer to error codes in Table 10-5.

Return Value
error

Parameter Discussion
counter is the counter to be used for the counting operation. The valid counters are shown in
Table 10-2, which is found in the Valid Counters for the Counter/Timer Functions subsection of
the Easy I/O for DAQ Library Function Overview section of this chapter.
dutyCycle is the desired ratio of the duration of the pulse phase (phase 2) to the period (phase 1
+ phase 2). The default of 0.5 generates a square wave.
•

If dutyCycle = 0.0, the function computes the closest achievable duty cycle using a
minimum pulse phase (phase 2) of three timebase cycles.

•

If dutyCycle = 1.0, the function computes the achievable duty cycle using a minimum delay
phase (phase 1) of three timebase cycles.

•

A duty cycle very close to 0.0 or 1.0 may not be possible.

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gateMode specifies how the signal on the counter's GATE pin is used. The options are:
•

UNGATED_SOFTWARE_START—ignore the gate signal and start when CounterStart is
called.

•

COUNT_WHILE_GATE_HIGH—count while the gate signal is TTL high after
CounterStart is called.

•

COUNT_WHILE_GATE_LOW—count while the gate signal is TTL low after
CounterStart is called.

•

START_COUNTING_ON_RISING_EDGE—start counting on the rising edge of the TTL
gate signal after CounterStart is called.

•

START_COUNTING_ON_FALLING_EDGE—start counting on the falling edge of the TTL
gate signal after CounterStart is called.

pulsePolarity is the polarity of phase 2 of each cycle. The options are:
•

POSITIVE_POLARITY—the delay (phase 1) is a low TTL level and the pulse (phase 2) is a
high level.

•

NEGATIVE_POLARITY—the delay (phase 1) is a high TTL level and the pulse (phase 2) is
a low level.

CounterEventOrTimeConfig
short error = CounterEventOrTimeConfig (short device, char counter[],
unsigned short counterSize,
double sourceTimebase,
unsigned short countLimitAction,
short sourceEdge,
unsigned short gateMode,
unsigned long *taskID);
Purpose
Configures one or two counters to count edges in the signal on the specified counter's SOURCE
pin or the number of cycles of a specified internal timebase signal.
When you use this function with the internal timebase and in conjunction with CounterStart
and CounterRead your program can make more precise timing measurements than with the
Timer function.
You can also call the CounterStart function to gate or trigger the operation with a signal on
the counter's GATE pin.

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Parameters
Input

Output

device

short
integer

Assigned by configuration utility.

counter

string

The counter to be used for the counting operation.

counterSize

unsigned
short
integer

Determines the size of the counter used to
perform the operation.

sourceTimebase

double

USE_COUNTER_SOURCE: count TTL edges at
counter’s SOURCE pin; or supply a valid
internal timebase frequency to count the TTL
edges of an internal clock.

countLimitAction

unsigned
short
integer

The action to take when the counter reaches
terminal count.

sourceEdge

short
integer

The edge of the counter source or timebase signal
on which it increments.

gateMode

unsigned
short
integer

Specifies how the signal on the counter's GATE
pin is used.

taskID

unsigned
long
integer

The reference number assigned for the counter
reserved for this operation. You pass taskID to
CounterStart, CounterRead, and
CounterStop.

short
integer

Refer to error codes in Table 10-5.

Return Value
error

Parameter Discussion
counter is the counter to be used for the counting operation. The valid counters are shown in
Table 10-2, which is found in the Valid Counters for the Counter/Timer Functions subsection of
the Easy I/O for DAQ Library Function Overview section of this chapter.
counterSize determines the size of the counter used to perform the operation.
•

For a device with DAQ-STC counters, counterSize must be ONE_COUNTER (24-bit).

•

For a device with Am9513 counters, counterSize can be ONE_COUNTER (16-bit) or
TWO_COUNTERS (32-bit).

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Chapter 10

If you use TWO_COUNTERS, counter+1 is cascaded with the specified counter. Counter+1 is
defined as shown in Table 10-3.
Table 10-3. Definition of Am 9513: Counter +1
counter

counter+1

1

2

2

3

3

4

4

5

5

1

6

7

7

8

8

9

9

10

10

6

sourceTimebase determines whether the counter uses its SOURCE pin or an internal timebase
as its signal source. Pass USE_COUNTER_SOURCE to count TTL edges at counter’s SOURCE
pin, or pass a valid internal timebase frequency to count the TTL edges of an internal clock.
Valid internal timebase frequencies are:
1000000
100000
10000
1000
100
20000000
100000

(Am9513)
(Am9513)
(Am9513)
(Am9513)
(Am9513)
(DAQ-STC)
(DAQ-STC)

countLimitAction is the action to take when the counter reaches terminal count. The parameter
accepts the following attributes:
•

COUNT_UNTIL_TC—count until terminal count, and set the overflow status when it is
reached. This mode is not available on the DAQ-STC.

•

COUNT_CONTINUOUSLY—count continuously. The Am9513 does not set the overflow
status at terminal count, but the DAQ-STC does.

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sourceEdge is the edge of the counter source or timebase signal on which it increments, and this
parameter accepts the following attributes:
•

COUNT_ON_RISING_EDGE

•

COUNT_ON_FALLING_EDGE

gateMode specifies how the signal on the counter's GATE pin is used. The options are:
•

UNGATED_SOFTWARE_START—ignore the gate signal and start when CounterStart is
called.

•

COUNT_WHILE_GATE_HIGH—count while the gate signal is TTL high after
CounterStart is called.

•

COUNT_WHILE_GATE_LOW—count while the gate signal is TTL low after
CounterStart is called.

•

START_COUNTING_ON_RISING_EDGE—start counting on the rising edge of the TTL
gate signal after CounterStart is called.

•

START_COUNTING_ON_FALLING_EDGE—start counting on the falling edge of the TTL
gate signal after CounterStart is called.

CounterMeasureFrequency
short error = CounterMeasureFrequency (short device, char counter[],
unsigned short counterSize,
double gateWidthSampleTimeinSec,
double maxDelayBeforeGateSec,
unsigned short counterMinus1GateMode,
double *actualGateWidthSec,
short *overflow, short *valid,
short *timeout, double *frequency);
Purpose
Measures the frequency of a TTL signal on the specified counter's SOURCE pin by counting
rising edges of the signal during a specified period of time. In addition to this connection, you
must also wire the counter's GATE pin to the OUT pin of counter-1. For a specified Counter,
Counter-1 and Counter+1 are defined as shown in Table 10-4.

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Table 10-4. Adjacent Counters
Am9513
counter-1

counter

counter+1

5

1

2

1

2

3

2

3

4

3

4

5

4

5

1

10

6

7

6

7

8

7

8

9

8

9

10

9

10

6

counter-1

counter

counter+1

1

0

1

0

1

0

DAQ-STC

This function is useful for relatively high frequency signals when many cycles of the signal occur
during the timing period. Use the PulseWidthOrPeriodMeasConfig function for
relatively low frequency signals. Keep in mind that
period = 1/frequency
This function configures the specified counter and counter+1 (optional) as event counters to
count rising edges of the signal on counter's SOURCE pin. The function also configures
counter-1 to generate a minimum-delayed pulse to gate the event counter, starts the event
counter and then the gate counter, waits the expected gate period, and then reads the gate
counter until its output state is low. Next the function reads the event counter and computes the
signal frequency (number of events/actual gate pulse width) and stops the counters. You can
optionally gate or trigger the operation with a signal on counter-1's GATE pin.

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Parameters
Input

Output

device

short
integer

Assigned by configuration utility.

counter

string

The counter to be used for the counting
operation.

counterSize

unsigned
short
integer

Determines the size of the counter used to
perform the operation: ONE_COUNTER or
TWO_COUNTERS.

gateWidthSampleTimeinSec double

The desired length of the pulse used to gate
the signal. The lower the signal frequency,
the longer the Gate Width must be.

maxDelayBeforeGateSec

double

The maximum expected delay between the
time the function is called and the start of
the gating pulse. If the gate signal does not
start in this time, a timeout occurs.

counterMinus1GateMode

unsigned
short
integer

The gate mode for counter-1.

actualGateWidthSec

double

The length in seconds of the gating pulse
that is used.

overflow

short
integer

1 = counter rolled past terminal count; 0 =
counter did not roll past terminal count. If
overflow is 1, the value of frequency is
inaccurate.

valid

short
integer

Set to 1 if the measurement completes
without a counter overflow. A timeout and
a valid measurement may occur at the same
time. A timeout does not produce an error.

timeout

short
integer

Set to 1 if the time limit expires during the
function call. A timeout and a valid
measurement may occur at the same time.
A timeout does not produce an error.

frequency

double

The frequency of the signal. It is computed
as the (number of rising edges) /
(actualGateWidthSec).

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Return Value
short
integer

error

Refer to error codes in Table 10-5.

Parameter Discussion
counter is the counter to be used for the counting operation. The valid counters are shown in
Table 10-2, which is found in the Valid Counters for the Counter/Timer Functions subsection of
the Easy I/O for DAQ Library Function Overview section of this chapter.
counterSize determines the size of the counter used to perform the operation.
•

For a device with DAQ-STC counters, counterSize must be ONE_COUNTER (24-bit).

•

For a device with Am9513 counters, counterSize can be ONE_COUNTER (16-bit) or
TWO_COUNTERS (32-bit).

•

If you use TWO_COUNTERS, counter+1 is cascaded with the specified counter. counter+1 is
defined as shown in Table 10-3 in the function description for
CounterEventOrTimeConfig.

counterMinus1GateMode is the gate mode for counter-1. The possible values are:
•

UNGATED_SOFTWARE_START

•

COUNT_WHILE_GATE_HIGH

•

COUNT_WHILE_GATE_LOW

•

START_COUNTING_ON_RISING_EDGE

counter-1 is used to gate counter so that rising edges are counted over a precise sample time.
For a specified counter, counter-1 is defined as shown in Table 10-4.

CounterRead
short error = CounterRead

(unsigned long taskID, short *overflow,
long *count);

Purpose
Reads the counter identified by taskID.

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Parameters
Input

taskID

unsigned long
integer

The reference number assigned to the counting
operation by one of the counter configuration
functions.

Output

overflow

short integer

1 = counter rolled past terminal count; 0 = counter
did not roll past terminal count.

count

long integer

The value of the counter at the time it is read.

short integer

Refer to error codes in Table 10-5.

Return Value
error
Parameter Discussion
overflow indicates whether the counter rolled over past its terminal count. If overflow is 1, the
value of count is inaccurate.

CounterStart
short error = CounterStart (unsigned long taskID);
Purpose
Starts the counter identified by taskID.
Parameters
Input

taskID

unsigned
long integer

The reference number assigned to the counting
operation by one of the counter configuration
functions.

short integer

Refer to error codes in Table 10-5.

Return Value
error

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CounterStop
short error = CounterStop (unsigned long taskID);
Purpose
Stops a count operation immediately.
Parameters
Input

taskID

unsigned
long integer

The reference number assigned to the
counting operation by one of the counter
configuration functions.

Return Value
error

short integer Refer to error codes in Table 10-5.

DelayedPulseGenConfig
short error = DelayedPulseGenConfig (short device, char counter[],
double pulseDelay, double pulseWidth,
unsigned short timebaseSource,
unsigned short gateMode,
unsigned short pulsePolarity,
double *actualDelay,
double *actualPulseWidth,
unsigned long *taskID);
Purpose
Configures a counter to generate a delayed TTL pulse or triggered pulse train on its OUT pin.
The signal is created by decrementing the counter twice, first for the delay to the pulse (phase 1),
then for the pulse itself (phase 2). The function selects the highest resolution timebase to achieve
the desired characteristics.
You can also call the CounterStart function to gate or trigger the operation with a signal on
the counter's GATE pin.

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Parameters
Input

Output

device

short integer

Assigned by configuration utility.

counter

string

The counter to be used for the counting
operation.

pulseDelay

double

The desired duration of the delay (phase 1)
before the pulse.

pulseWidth

double

The desired duration of the pulse (phase 2)
after the delay.

timebaseSource

unsigned short
integer

The signal that causes the counter to count.

gateMode

unsigned short
integer

Specifies how the signal on the counter's
GATE pin is used.

pulsePolarity

unsigned short
integer

The polarity of phase 2 of each cycle.

actualDelay

double

The achieved delay based on the resolution
and range of your hardware.

actualPulseWidth

double

The achieved pulse width based on the
resolution and range of your hardware.

taskID

unsigned long
integer

The reference number assigned to this
operation. You pass taskID to
CounterStart, CounterRead, and
CounterStop.

short integer

Refer to error codes in Table 10-5.

Return Value
error
Parameter Discussion
counter is the counter to be used for the counting operation. The valid counters are shown in
Table 10-2, which is found in the Valid Counters for the Counter/Timer Functions subsection of
the Easy I/O for DAQ Library Function Overview section of this chapter.
pulseDelay is the desired duration of the delay (phase 1) before the pulse. This parameter accepts
the following attributes:
•

The unit is seconds if timebaseSource is USE_INTERNAL_TIMEBASE and cycles if
timebaseSource is USE_COUNTER_SOURCE.

•

If pulseDelay = 0.0 and timebaseSource is internal, the function selects a minimum delay of
three cycles of the timebase used.

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•

pulseWidth is the desired duration of the pulse (phase 2) after the delay

•

The unit is seconds if timebaseSource is USE_INTERNAL_TIMEBASE and cycles if
timebaseSource is USE_COUNTER_SOURCE.

•

If pulseDelay = 0.0 and timebaseSource is internal, the function selects a minimum delay of
three cycles of the timebase used.

timebaseSource is the signal that causes the counter to count. This parameter accepts the
following attributes:
•

USE_INTERNAL_TIMEBASE—An internal timebase is selected based on the pulse delay
and width, in units of seconds.

•

USE_COUNTER_SOURCE—The signal on the counter's SOURCE pin is used and the units
of pulse delay and width are cycles of that signal.

gateMode specifies how the signal on the counter's GATE pin is used. This parameter accepts
the following attributes:
•

UNGATED_SOFTWARE_START—ignore the gate signal and start when CounterStart is
called.

•

COUNT_WHILE_GATE_HIGH—count while the gate signal is TTL high after
CounterStart is called.

•

COUNT_WHILE_GATE_LOW—count while the gate signal is TTL low after
CounterStart is called.

•

START_COUNTING_ON_RISING_EDGE—start counting on the rising edge of the TTL
gate signal after CounterStart is called.

•

START_COUNTING_ON_FALLING_EDGE—start counting on the falling edge of the TTL
gate signal after CounterStart is called.

•

RESTART_ON_EACH_RISING_EDGE—restart counting on each rising edge of the TTL
gate signal after CounterStart is called.

•

RESTART_ON_EACH_FALLING_EDGE—restart counting on each falling edge of the TTL
gate signal after CounterStart is called.

pulsePolarity is the polarity of phase 2 of each cycle. This parameter accepts the following
attributes:
•

POSITIVE_POLARITY—the delay (phase 1) is a low TTL level and the pulse (phase 2) is a
high level.

•

NEGATIVE_POLARITY—the delay (phase 1) is a high TTL level and the pulse (phase 2) is
a low level.

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FrequencyDividerConfig
short error = FrequencyDividerConfig (short device, char counter[],
double sourceTimebase,
double timebaseDivisor,
unsigned short gateMode,
unsigned short outputBehavior,
short sourceEdge, unsigned long *taskID);
Purpose
This function configures the specified counter to count the number of signal transitions on its
SOURCE pin or on an internal timebase signal, and to strobe or toggle the signal on its OUT pin.
To divide an external TTL signal, connect it to counter's SOURCE pin, and set the
sourceTimebase parameter to USE_COUNTER_SOURCE.
To divide an internal timebase signal, set the sourceTimebase parameter to a desired valid
frequency.
Set the timebaseDivisor to the desired value. For a value of N and a pulsed output, an output
pulse equal to the period of the source or timebase signal appears on counter's OUT pin once
each N cycles of that signal. For a toggled output, the output toggles after each N cycles. The
toggled output frequency is thus half that of the pulsed output, in other words,
pulsedFrequency = sourceFrequency/N
and
toggledFrequency = sourceFrequency/(2*N)
thus, if N=3, the OUT pin would generate pulses as follows:
_
_
_
_
_
_
_
_
_
_
_
_
_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |
___
___
___
___
pulsed _|
|_______|
|_______|
|_______|
|______
___________
___________
toggled _|
|___________|
|_________
source

If gateMode is not UNGATED_SOFTWARE_START, connect your gate signal to counter's
GATE pin.

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Parameters
Input

Output

device

short integer

Assigned by configuration utility.

counter

string

The counter to be used for the counting
operation.

sourceTimebase

double

USE_COUNTER_SOURCE: count TTL edges at
counter’s SOURCE pin; or supply a valid
internal timebase frequency to count the TTL
edges of an internal clock.

timebaseDivisor

double

The source frequency divisor.

gateMode

unsigned
short integer

Specifies how the signal on the counter's GATE
pin is used.

outputBehavior

unsigned
short integer

The behavior of the output signal when counter
reaches terminal count.

sourceEdge

short integer

The edge of the counter source or timebase signal
on which it decrements:
COUNT_ON_RISING_EDGE or
COUNT_ON_FALLING_EDGE.

taskID

unsigned
long integer

The reference number assigned to this operation.
You pass taskID to CounterStart,
CounterRead, and CounterStop.

Return Value
short integer Refer to error codes in Table 10-5.

error
Parameter Discussion

counter is the counter to be used for the counting operation. The valid counters are shown in
Table 10-2, which is found in the Valid Counters for the Counter/Timer Functions subsection of
the Easy I/O for DAQ Library Function Overview section of this chapter.
sourceTimebase determines whether the counter uses its SOURCE pin or an internal timebase
as its signal source. Pass USE_COUNTER_SOURCE to count TTL edges at counter’s SOURCE
pin, or pass a valid internal timebase frequency to count the TTL edges of an internal clock.
Valid internal timebase frequencies are:
1000000
100000
10000
1000
100
20000000
100000

(Am9513)
(Am9513)
(Am9513)
(Am9513)
(Am9513)
(DAQ-STC)
(DAQ-STC)

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timebaseDivisor is the source frequency divisor. For example, if the source signal is 1000 Hz,
the timebaseDivisor is 10, and the output is pulsed, the frequency of the counter's OUT signal is
100 Hz. If the output is toggled, the frequency is 50 Hz.
gateMode specifies how the signal on the counter's GATE pin is used. This parameter accepts
the following attributes:
•

UNGATED_SOFTWARE_START—ignore the gate signal and start when CounterStart is
called.

•

COUNT_WHILE_GATE_HIGH—count while the gate signal is TTL high after
CounterStart is called.

•

COUNT_WHILE_GATE_LOW—count while the gate signal is TTL low after
CounterStart is called.

•

START_COUNTING_ON_RISING_EDGE—start counting on the rising edge of the TTL
gate signal after CounterStart is called.

•

START_COUNTING_ON_FALLING_EDGE—start counting on the falling edge of the TTL
gate signal after CounterStart is called.

outputBehavior is the behavior of the output signal when counter reaches terminal count. This
parameter accepts the following attributes:
•

HIGH_PULSE—high pulse lasting one cycle of the source or timebase signal.

•

LOW_PULSE—low pulse lasting one cycle of the source or timebase signal.

•

HIGH_TOGGLE—high toggle lasting until the next TC.

•

LOW_TOGGLE—low toggle lasting until the next TC.

For a Timebase Divisor of N and a pulsed output, an output pulse equal to the period of the
source or timebase signal appears on counter's OUT pin once each N cycles of that signal For a
toggled output, the output toggles after each N cycles. The toggled output frequency is thus half
that of the pulsed output, in other words,
pulsedFrequency = sourceFrequency/ N
and
toggledFrequency = sourceFrequency/(2*N)
thus, if N =3, the OUT pin would generate pulses as follows:
_
_
_
_
_
_
_
_
_
_
_
_
_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |
___
___
___
___
HIGH_PULSE _|
|_______|
|_______|
|_______|
|______
___________
___________
HIGH_TOGGLE _|
|___________|
|_________
source

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GetAILimitsOfChannel
short error = GetAILimitsOfChannel (short device, char channelString[],
char singleChannel[],
double initialHighLimitVolts,
double initialLowLimitVolts,
double *highLimitVolts,
double *lowLimitVolts);
Purpose
Returns the high and low limits for a particular channel in the channel string.
Parameters
Input

Output

device

short
integer

Assigned by configuration utility.

channelString

string

Analog input channels that are to be sampled.

singleChannel

string

A single channel of the channel string.

initialHighLimitVolts

double

Specifies the maximum voltage to be measured
for all channels in the channel string listed
before a command string that specifies a new
high limit.

initialLowLimitVolts

double

The minimum voltage to be measured for all
channels in the channel string listed before a
command string that specifies a new low limit.

highLimitVolts

double

Returns the high limit for the specified channel.

lowLimitVolts

double

Returns the low limit for the specified channel.

short
integer

Refer to error codes in Table 10-5.

Return Value
error

Parameter Discussion
channelString is the analog input channels that are to be sampled. Refer to the Channel String
for Analog Input Functions subsection of the Easy I/O for DAQ Library Function Overview
section of this chapter for the syntax of this string.
singleChannel is a single channel of the channel string. For example, if the channel string is
"0:3,5"
a single channel could be
"2" or "5" and so on.

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initialHighLimitVolts specifies the maximum voltage that is measured for all channels in the
channel string listed before a command string that specifies a new high limit. For the following
channel string:
"0,1; cmd hi 10.0 low -10.0; 2,3"

If initialHighLimitVolts is 5.0, channels "0" and "1" have a high limit of 5.0 and channels
"2" and "3" have a high limit of 10.0.
initialLowLimitVolts is the minimum voltage that is measured for all channels in the channel
string listed before a command string that specifies a new low limit. For the following channel
string:
"0,1; cmd hi 10.0 low -10.0; 2,3"

If the initialLowLimitVolts is -5.0, channels "0" and "1" have a low limit of -5.0 and channels
"2" and "3" have a low limit of -10.0.

GetChannelIndices
short error = GetChannelIndices (short device, char channelString[],
char channelSubString[], short channelType,
long channelIndices[]);
Purpose
Determines the indices of the channels in the channelSubString. For example, if the
channelString is
"1:6"

and the channelSubString is
"1,3,6"

the channelIndices array would be filled as follows:
channelIndices[0] = 0;
channelIndices[1] = 2;
channelIndices[2] = 5;
This function is useful if you want to verify that a particular channel is part of the
channelString.

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Parameters
Input

Output

device

short integer Assigned by configuration utility.

channelString

string

The analog channel string.

channelSubString

string

A sub-string of the channelString.

channelType

short integer Specifies whether the channelString is
ANALOG_INPUT or ANALOG_OUTPUT.

channelIndices

long integer
array

Returns the indices of the channels in the
channelSubString.

Return Value
error

short integer Refer to error codes in Table 10-5.

Parameter Discussion
channelString is the analog channels that are to be sampled. Refer to the Channel String for
Analog Input Functions subsection of the Easy I/O for DAQ Library Function Overview section
of this chapter for the syntax of this string.
channelSubString is a sub-string of the channelString. For example, if the channelString is
"0:3,5"

the sub-string could be
"2" or
"1,3"

GetChannelNameFromIndex
short error = GetChannelNameFromIndex (short device, char channelString[],
long index, short channelType,
char channelName[]);
Purpose
Determines the name of the particular channel in the channelString indicated by index.

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Parameters
Input

Output

device

short integer

Assigned by configuration utility.

channelString

string

Analog input channels that are to be sampled.

index

long integer

The index of a particular channel in the
channelString.

channelType

short integer

Specifies whether the channelString is
ANALOG_INPUT or ANALOG_OUTPUT.

channelName

string

Returns the name of the particular channel in the
channelString indicated by index.

short integer

Refer to error codes in Table 10-5.

Return Value
error
Parameter Discussion
channelString is the analog channels that are to be sampled. Refer to the Channel String for
Analog Input Functions or Channel String for Analog Output Functions subsection of the Easy
I/O for DAQ Library Function Overview section of this chapter for the syntax of this string.
channelName returns the name of the particular channel in the channelString indicated by
index. This string should be declared to have MAX_CHANNEL_NAME_LENGTH bytes.

GetDAQErrorString
char *errorString = GetDAQErrorString (short errorNumber);
Purpose
This function returns a string containing the description for the numeric error code.
Parameters
Input

errorNumber

short
integer

The error number that was returned from an
Easy I/O for DAQ function.

string

The string containing the description for the
numeric error code.

Return Value
errorString

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GetNumChannels
short error = GetNumChannels (short device, char channelString[],
short channelType,
unsigned long *numberOfChannels);
Purpose
Determines the number of channels contained in the channelString.
You need to know the number of channels in the channelString so that you can interpret (for
analog input) or build (for analog output) waveform arrays correctly.
Parameters
Input

Output

device

short
integer

Assigned by configuration utility.

channelString

string

The analog channel string.

channelType

short
integer

Specifies whether the channelString is
ANALOG_INPUT or ANALOG_OUTPUT.

numberOfChannels

unsigned
long integer

Returns the number of channels contained in
the channelString.

short
integer

Refer to error codes in Table 10-5.

Return Value
error

Parameter Discussion
channelString is the analog channels that are to be sampled. Refer to the Channel String for
Analog Input Functions or Channel String for Analog Output Functions subsection of the Easy
I/O for DAQ Library Function Overview section of this chapter for the syntax of this string.

GroupByChannel
short error = GroupByChannel (float array[], long numberOfScans,
unsigned long numberOfChannels);
Purpose
This function can be used to reorder an array of data from "grouped by scan" mode into "grouped
by channel" mode.

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If you acquire data in "grouped by scan" mode, you need to reorder the array into "grouped by
channel" mode before it can be passed to graph plotting functions, analysis functions, and others.
See the description of the fillMode parameter of AIAcquireWaveforms for an explanation of
"grouped by scan" versus "grouped by channel".
Parameters
Input/ array
Output

double
array

Pass in the “grouped by scan” array and it is
grouped by channel in place.

Input

numberOfScans

long integer

The number of scans contained in the data
array.

numberOfChannels

unsigned
long integer

Specifies the number of channels that were
scanned. You can use GetNumChannels to
determine the number of channels contained in
your channel string.

short integer

Refer to error codes in Table 10-5.

Return Value
error

ICounterControl
short error = ICounterControl (short device, short counter, short controlCode,
unsigned short count, short binaryorBCD,
short outputState, unsigned short *readValue);
Purpose
Controls counters on devices that use the 8253 timer chip (Lab boards, SCXI-1200,
DAQPad-1200, PC-LPM-16, DAQCard 700).

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Parameters
Input

Output

device

short integer

Assigned by configuration utility.

counter

short integer

The counter to be controlled (valid counters are
0 through 2).

controlCode

short integer

Determines the counter's operating mode.

count

unsigned
short integer

The period between output pulses.

binaryorBCD

short integer

I_BINARY: The counter operates as a 16-bit
binary counter (0 to 65,535); I_BCD: The
counter operates as a 4-decade BCD counter (0
to 9,999).

outputState

short integer

I_HIGH_STATE: Output state of the counter is
high; I_LOW_STATE: Output state of the
counter is low. Valid when the controlCode = 7
(I_RESET).

readValue

unsigned
short integer

Returns the value read from the counter when
controlCode = 6 (I_READ).

short integer

Refer to error codes in Table 10-5.

Return Value
error
Parameter Discussion
controlCode determines the counter's operating mode. This parameter accepts the following
attributes:
•

0: I_TOGGLE_ON_TC—counter's output becomes low after the mode set operation and the
counter decrements from count to 0 while the gate is high. The output toggles from low to
high once the counter reaches 0.

•

1: I_PROGRAMMABLE_ONE_SHOT—counter's output becomes low on the count following
the leading edge of the gate input and becomes high on TC.

•

2: I_RATE_GENERATOR—counter's output becomes low for one period of the clock input.
The count indicates the period between output pulses.

•

3: I_SQUARE_WAVE_RATE_GENERATOR—counter's output stays high for one-half of the
count clock pulses and stays low for the other half.

•

4: I_SOFTWARE_TRIGGERED_STROBE—counter's output is initially high, and the
counter begins to count down while the gate input is high. On terminal count, the output
becomes low for on clock pulse, then becomes high again.

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•

5: I_HARDWARE_TRIGGERED_STROBE—similar to mode 4, except that a rising edge at
the gate input triggers the count to start.

•

6: I_READ—read the counter and return the value in the readValue parameter.

•

7: I_RESET—resets the counter and sets its output to outputState.

count is the period between output pulses. This parameter accepts the following attributes:
•

If controlCode is 0, 1, 4, or 5, count can be 0 through 65,535 in binary counter operation
and 0 through 9,999 in binary-coded decimal (BCD) counter operation.

•

If controlCode is 2 or 3, count can be 2 through 65,535 in binary counter operation and 2
through 9,999 in BCD counter operation.

Note: 0 is equivalent to 65,535 in binary counter operation and 10,000 in BCD counter
operation.

PlotLastAIWaveformsPopup
short error = PlotLastAIWaveformsPopup (short device, double waveformsBuffer[]);
Purpose
This function plots the last AI waveform that was acquired. It is intended for demonstration
purposes.
Data must be grouped by channel before it is passed to this function:
Either use the GROUP_BY_CHANNEL as the fillMode parameter when acquiring the data or call
GroupByChannel before calling this function.
Parameters
Input

device

short integer

Assigned by configuration utility.

waveformsBuffer

double array

Array containing the last AI waveform acquired.

short integer

Refer to error codes in Table 10-5.

Return Value
error

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PulseWidthOrPeriodMeasConfig
short error = PulseWidthOrPeriodMeasConfig (short device, char counter[],
unsigned short typeOfMeasurement,
double sourceTimebase,
unsigned long *taskID);
Purpose
Configures the specified counter to measure the pulse width or period of a TTL signal connected
to its GATE pin. The measurement is done by counting the number of cycles of the specified
timebase between the appropriate starting and ending events.
Connect the signal you want to measure to the counter's GATE pin.
To measure with an internal timebase, set sourceTimebase to the desired frequency.
To measure with an external timebase, connect that signal to counter's SOURCE pin and set the
sourceTimebase parameter to USE_COUNTER_SOURCE.
Call CounterStart to start the measurement. Then call CounterRead to read the value. A
valid count value is greater than 3 without overflow.
Parameters
Input

device

short
integer

Assigned by configuration utility.

counter

string

The counter to be used for the counting
operation.

typeOfMeasurement unsigned
short
integer

Output

Identifies the type of pulse width or period
measurement to make.

sourceTimebase

double

USE_COUNTER_SOURCE: count TTL edges
at counter’s SOURCE pin; or supply a valid
internal timebase frequency to count the TTL
edges of an internal clock.

taskID

unsigned
The reference number assigned for the counter
long integer reserved for this operation. You pass taskID
to CounterStart, CounterRead, and
CounterStop.

Return Value
error

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Parameter Discussion
typeOfMeasurement identifies the type of pulse width or period measurement to make. This
parameter accepts the following attributes:
•

MEASURE_HIGH_PULSE_WIDTH—measure high pulse width from rising to falling edge.

•

MEASURE_LOW_PULSE_WIDTH—measure low pulse width from falling to rising edge.

•

MEASURE_PERIOD_BTW_RISING_EDGES—measure period between adjacent rising
edges.

•

MEASURE_PERIOD_BTW_FALLING_EDGES—measure period between adjacent falling
edges.

sourceTimebase determines whether the counter uses its SOURCE pin or an internal timebase
as its signal source. Pass USE_COUNTER_SOURCE to count TTL edges at counter’s SOURCE
pin, or pass a valid internal timebase frequency to count the TTL edges of an internal clock.
Valid internal timebase frequencies are:
1000000
100000
10000
1000
100
20000000
100000

(Am9513)
(Am9513)
(Am9513)
(Am9513)
(Am9513)
(DAQ-STC)
(DAQ-STC)

ReadFromDigitalLine
short error = ReadFromDigitalLine (short device, char portNumber[], short line,
short portWidth, long configure,
unsigned long *lineState);
Purpose
Reads the logical state of a digital line on a port that you configure as input.

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Parameters
Input

Output

device

short integer

Assigned by configuration utility.

portNumber

string

Specifies the digital port this function
configures.

line

short integer

Specifies the individual bit or line within the
port to be used for I/O (zero-based).

portWidth

short integer

The total width in bits of the port. For example,
you can combine two 4-bit ports into an 8-bit
port on an MIO (non E-Series) board by setting
portWidth to 8.

configure

long integer

1: Configure the digital port before reading;
0: Don’t configure the digital port before
reading. When this function is called in a loop,
it can be optimized by only configuring the
digital port on the first iteration.

lineState

unsigned
long integer

Returns the state of the digital line. 1 = logical
high; 0 = logical low.

Return Value
error

short integer Refer to error codes in Table 10-5.

Parameter Discussion
portNumber specifies the digital port this function configures.
•

A portNumber value of 0 signifies port 0, a portNumber of 1 signifies port 1, and so on. If
you use an SCXI-1160, SCXI-1161, SCXI-1162, or SCXI-1163 module, use the
"SCx!MDy!0"
syntax, where x is the chassis ID and y is the module device number, to specify the port on a
module.

portWidth is the total width in bits of the port. For example, you can combine two 4-bit ports
into an 8-bit port on an MIO (non E-Series) board by setting portWidth to 8.
•

When portWidth is greater than the physical port width of a digital port, the following
restrictions apply. The portWidth must be an integral multiple of the physical port width,
and the port numbers in the combined port must begin with the port named by portNumber
and must increase consecutively. For example, if portNumber is 3 and portWidth is
24(bits), LabWindows/CVI uses ports 3, 4, and 5.

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•

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The portWidth for the 8255-based digital I/O ports (including all digital ports on Lab
boards, SCXI-1200, DAQPad-1200, DAQCard-1200, DIO-24, DIO-32F, DIO-96, and
AT-MIO-16DE-10/AT-MIO-16D ports 2, 3 and 4) should be at least 8.

configure specifies whether to configure the digital port before reading.
•

When this function is called in a loop, it can be optimized by only configuring the digital port
on the first iteration.

•

When you configure a digital I/O port that is part of an 8255 PPI (including all digital ports
on Lab boards, SCXI-1200, DAQPad-1200, DAQCard-1200, DIO-24, DIO-32F, DIO-96,
and AT-MIO-16DE-10/AT-MIO-16D ports 2, 3 and 4), the 8255 PPI goes through a
configuration phase, where all the ports within the same PPI chip get reset to logic low,
regardless of the data direction. The data directions on other ports, however, are maintained.

ReadFromDigitalPort
short error = ReadFromDigitalPort (short device, char portNumber[],
short portWidth, long configure,
unsigned long *pattern);
Purpose
Reads a digital port that you configure for input.
Parameters
Input

Output

device

short integer

Assigned by configuration utility.

portNumber

string

Specifies the digital port this function
configures.

line

short integer

Specifies the individual bit or line within the port
to be used for I/O.

portWidth

short integer

The total width in bits of the port. For example,
you can combine two 4-bit ports into an 8-bit
port on an MIO (non E-Series) board by setting
portWidth to 8.

configure

long integer

1: Configure the digital port before reading;
0: Don’t configure the digital port before
reading. When this function is called in a loop, it
can be optimized by only configuring the digital
port on the first iteration.

pattern

unsigned
long integer

The data read from the digital port.

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Return Value
error

short integer

Refer to error codes in Table 10-5.

Parameter Discussion
portNumber specifies the digital port this function configures.
A portNumber value of 0 signifies port 0, a portNumber of 1 signifies port 1, and so on. If you
use an SCXI-1160, SCXI-1161, SCXI-1162, or SCXI-1163 module, use the
"SCx!MDy!0"
syntax, where x is the chassis ID and y is the module device number, to specify the port on a
module.
portWidth is the total width in bits of the port. For example, you can combine two 4-bit ports
into an 8-bit port on an MIO (non E-Series) board by setting portWidth to 8.
•

When portWidth is greater than the physical port width of a digital port, the following
restrictions apply. The portWidth must be an integral multiple of the physical port width,
and the port numbers in the combined port must begin with the port named by portNumber
and must increase consecutively. For example, if portNumber is 3 and portWidth is
24(bits), LabWindows/CVI uses ports 3, 4, and 5.

•

The portWidth for the 8255-based digital I/O ports (including all digital ports on Lab
boards, SCXI-1200, DAQPad-1200, DAQCard-1200, DIO-24, DIO-32F, DIO-96, and
AT-MIO-16DE-10/AT-MIO-16D ports 2, 3 and 4) should be at least 8.

configure specifies whether to configure the digital port before reading.
•

When this function is called in a loop, it can be optimized by only configuring the digital port
on the first iteration.

•

When you configure a digital I/O port that is part of an 8255 PPI (including all digital ports
on Lab boards, SCXI-1200, DAQPad-1200, DAQCard-1200, DIO-24, DIO-32F, DIO-96,
and AT-MIO-16DE-10/AT-MIO-16D ports 2, 3 and 4), the 8255 PPI goes through a
configuration phase, where all the ports within the same PPI chip get reset to logic low,
regardless of the data direction. The data directions on other ports, however, are maintained.

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SetEasyIOMultitaskingMode
void SetEasyIOMultitaskingMode (int multitaskingMode);
Purpose
By default, if you call the non-timed Easy I/O for DAQ functions repetitively, these functions do
not reconfigure the hardware unless you change the parameters to the functions. Thus, the
performance of these functions is improved by only reconfiguring the hardware when necessary.
However, if you run multiple data acquisition programs simultaneously, any non-timed Easy I/O
for DAQ functions will not know when the hardware has been reconfigured by another
application accessing the same DAQ device, and the functions will run incorrectly.
To get around this problem, you can force these functions to always reconfigure the hardware by
setting the multitasking mode to MULTITASKING_AWARE.
You should set the multitasking mode to MULTITASK_AWARE if your program calls the nontimed Easy I/O for DAQ functions and you expect another data acquisition program to be
accessing the same board while your program is running. In this mode, the Easy I/O for DAQ
functions always reconfigure the hardware on each invocation, which means they will not be
adversely affected by other applications but they will not be optimized for speed.
You should set the multitasking mode to MULTITASK_UNAWARE if you know there will not be
another program accessing the same DAQ device while your program is running.
Parameters
Input

multitaskingMode

integer

When activated, DAQ devices are reconfigured
to default settings every time an Easy I/O for
DAQ function invokes such devices.

Return Value
None.

WriteToDigitalLine
short error = WriteToDigitalLine (short device, char portNumber[], short line,
short portWidth, long configure,
unsigned long lineState);
Purpose
Sets the output logic state of a digital line on a digital port.

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Parameters
Input

device

short integer

Assigned by configuration utility.

portNumber

string

Specifies the digital port this function configures.

line

short integer

Specifies the individual bit or line within the port to
be used for I/O.

portWidth

short integer

The total width in bits of the port. For example, you
can combine two 4-bit ports into an 8-bit port on an
MIO (non E-Series) board by setting portWidth
to 8.

configure

long integer

1: Configure the digital port before writing; 0: Don’t
configure the digital port before writing. When this
function is called in a loop, it can be optimized by
only configuring the digital port on the first
iteration.

lineState

unsigned long
integer

Specifies the new state of the digital line. 1 = logical
high; 0 = logical low.

short integer

Refer to error codes in Table 10-5.

Return Value
error
Parameter Discussion
portNumber specifies the digital port this function configures.
A portNumber value of 0 signifies port 0, a portNumber of 1 signifies port 1, and so on. If you
use an SCXI-1160, SCXI-1161, SCXI-1162, or SCXI-1163 module, use the
"SCx!MDy!0"

syntax, where x is the chassis ID and y is the module device number, to specify the port on a
module.
portWidth is the total width in bits of the port. For example, you can combine two 4-bit ports
into an 8-bit port on an MIO (non E-Series) board by setting portWidth to 8.
•

When portWidth is greater than the physical port width of a digital port, the following
restrictions apply. The portWidth must be an integral multiple of the physical port width,
and the port numbers in the combined port must begin with the port named by portNumber
and must increase consecutively. For example, if portNumber is 3 and portWidth is
24(bits), LabWindows/CVI uses ports 3, 4, and 5.

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The portWidth for the 8255-based digital I/O ports (including all digital ports on Lab
boards, SCXI-1200, DAQPad-1200, DAQCard-1200, DIO-24, DIO-32F, DIO-96, and
AT-MIO-16DE-10/AT-MIO-16D ports 2, 3 and 4) should be at least 8.

configure specifies whether to configure the digital port before writing.
•

When this function is called in a loop, it can be optimized by only configuring the digital port
on the first iteration.

•

When you configure a digital I/O port that is part of an 8255 PPI (including all digital ports
on Lab boards, SCXI-1200, DAQPad-1200, DAQCard-1200, DIO-24, DIO-32F, DIO-96,
and AT-MIO-16DE-10/AT-MIO-16D ports 2, 3 and 4), the 8255 PPI goes through a
configuration phase, where all the ports within the same PPI chip get reset to logic low,
regardless of the data direction. The data directions on other ports, however, are maintained.

WriteToDigitalPort

short error = WriteToDigitalPort (short device, char portNumber[], short portWidth,
long configure, unsigned long pattern);
Purpose
Outputs a decimal pattern to a digital port.
Parameters
Input

device

short integer

Assigned by configuration utility.

portNumber

string

Specifies the digital port this function configures.

portWidth

short integer

The total width in bits of the port. For example,
you can combine two 4-bit ports into an 8-bit port
on an MIO (non E-Series) board by setting
portWidth to 8.

configure

long integer

1: Configure the digital port before writing;
0: Don’t configure the digital port before writing.
When this function is called in a loop, it can be
optimized by only configuring the digital port on
the first iteration.

pattern

unsigned
long integer

Specifies the new state of the lines in the port.

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Return Value
error

short integer

Refer to error codes in Table 10-5.

Parameter Discussion
portNumber specifies the digital port this function configures.
A portNumber value of 0 signifies port 0, a portNumber of 1 signifies port 1, and so on. If you
use an SCXI-1160, SCXI-1161, SCXI-1162, or SCXI-1163 module, use the
"SCx!MDy!0"

syntax, where x is the chassis ID and y is the module device number, to specify the port on a
module.
portWidth is the total width in bits of the port. For example, you can combine two 4-bit ports
into an 8-bit port on an MIO (non E-Series) board by setting portWidth to 8.
•

When portWidth is greater than the physical port width of a digital port, the following
restrictions apply. The portWidth must be an integral multiple of the physical port width,
and the port numbers in the combined port must begin with the port named by portNumber
and must increase consecutively. For example, if portNumber is 3 and portWidth is
24(bits), LabWindows/CVI uses ports 3, 4, and 5.

•

The portWidth for the 8255-based digital I/O ports (including all digital ports on Lab
boards, SCXI-1200, DAQPad-1200, DAQCard-1200, DIO-24, DIO-32F, DIO-96, and
AT-MIO-16DE-10/AT-MIO-16D ports 2, 3 and 4) should be at least 8.

configure specifies whether to configure the digital port before writing.
•

When this function is called in a loop, it can be optimized by only configuring the digital port
on the first iteration.

•

When you configure a digital I/O port that is part of an 8255 PPI (including all digital ports
on Lab boards, SCXI-1200, DAQPad-1200, DAQCard-1200, DIO-24, DIO-32F, DIO-96,
and AT-MIO-16DE-10/AT-MIO-16D ports 2, 3 and 4), the 8255 PPI goes through a
configuration phase, where all the ports within the same PPI chip get reset to logic low,
regardless of the data direction. The data directions on other ports, however, are maintained.

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Error Conditions
All of the functions in the Easy I/O for DAQ Library return an error code. A negative number
indicates that an error occurred. If the return value is positive, it has the same description as if it
were negative, but it is considered a warning.
Table 10-5. Easy I/O for DAQ Error Codes
0

Success.

-10001 syntaxErr An error was detected in the input string; the arrangement or ordering of
the characters in the string is not consistent with the expected ordering.
-10002 semanticsErr An error was detected in the input string; the syntax of the string is
correct, but certain values specified in the string are inconsistent with other values
specified in the string.
-10003 invalidValueErr The value of a numeric parameter is invalid.
-10004 valueConflictErr The value of a numeric parameter is inconsistent with another
parameter, and the combination is therefore invalid.
-10005 badDeviceErr The device parameter is invalid.
-10006 badLineErr The line parameter is invalid.
-10007 badChanErr A channel is out of range for the device type or input configuration, the
combination of channels is invalid, or you must reverse the scan order so that
channel 0 is last.
-10008 badGroupErr The group parameter is invalid.
-10009 badCounterErr The counter parameter is invalid.
-10010 badCountErr The count parameter is too small or too large for the specified counter.
-10011 badIntervalErr The interval parameter is too small or too large for the associated
counter or I/O channel.
-10012 badRangeErr The analog input or analog output voltage range is invalid for the
specified channel.
-10013 badErrorCodeErr The driver returned an unrecognized or unlisted error code.
-10014 groupTooLargeErr The group size is too large for the device.
-10015 badTimeLimitErr The time limit parameter is invalid.
-10016 badReadCountErr The read count parameter is invalid.
-10017 badReadModeErr The read mode parameter is invalid.
-10018 badReadOffsetErr The offset is unreachable.
(continues)

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Table 10-5. Easy I/O for DAQ Error Codes (Continued)
-10019 badClkFrequencyErr The frequency parameter is invalid.
-10020 badTimebaseErr The timebase parameter is invalid.
-10021 badLimitsErr The limits are beyond the range of the device.
-10022 badWriteCountErr Your data array contains an incomplete update, or you are
trying to write past the end of the internal buffer, or your output operation is
continuous and the length of your array is not a multiple of one half of the internal
buffer size.
-10023 badWriteModeErr The write mode is out of range or is invalid.
-10024 badWriteOffsetErr The write offset plus the write mark is greater than the internal
buffer size or it must be set to 0.
-10025 limitsOutOfRangeErr The voltage limits are out of range for this device in the
current configuration. Alternate limits were selected.
-10026 badInputBufferSpecification The input buffer specification is invalid. This error
results if, for example, you try to configure a multiple-buffer acquisition for a device
that cannot perform multiple-buffer acquisition.
-10027 badDAQEventErr For DAQEvents 0 and 1, general value A must be greater than 0
and less than the internal buffer size. If DMA is used for DAQEvent 1, general value
A must divide the internal buffer size evenly, with no remainder. If the TIO-10 is
used for DAQEvent 4, general value A must be 1 or 2.
-10028 badFilterCutoffErr The cutoff frequency is not valid for this device.
-10080 badGainErr The gain parameter is invalid.
-10081 badPretrigCountErr The pretrigger sample count is invalid.
-10082 badPosttrigCountErr The posttrigger sample count is invalid.
-10083 badTrigModeErr The trigger mode is invalid.
-10084 badTrigCountErr The trigger count is invalid.
-10085 badTrigRangeErr The trigger range or trigger hysteresis window is invalid.
-10086 badExtRefErr The external reference value is invalid.
-10087 badTrigTypeErr The trigger type parameter is invalid.
-10088 badTrigLevelErr The trigger level parameter is invalid.
-10089 badTotalCountErr The total count specified is inconsistent with the buffer
configuration and pretrigger scan count or with the device type.
-10090 badRPGErr The individual range, polarity, and gain settings are valid but the
combination specified is invalid for this device.
(continues)

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Table 10-5. Easy I/O for DAQ Error Codes (Continued)
-10091 badIterationsErr The analog output buffer iterations count is invalid. It must be 0
(for indefinite iterations) or 1.
-10100 badPortWidthErr The requested digital port width is not a multiple of the hardware
port width.
-10240 noDriverErr The driver interface could not locate or open the driver.
-10241 oldDriverErr The driver is out of date.
-10242 functionNotFoundErr The specified function is not located in the driver.
-10243 configFileErr The driver could not locate or open the configuration file, or the
format of the configuration file is not compatible with the currently installed driver.
-10244 deviceInitErr The driver encountered a hardware-initialization error while
attempting to configure the specified device.
-10245 osInitErr The driver encountered an operating system error while attempting to
perform an operation, or the driver performed an operation that the operating system
does not recognize.
-10246 communicationsErr The driver is unable to communicate with the specified external
device.
-10247 cmosConfigErr The CMOS configuration memory for the computer is empty or
invalid, or the configuration specified does not agree with the current configuration of
the computer.
-10248 dupAddressErr The base addresses for two or more devices are the same;
consequently, the driver is unable to access the specified device.
-10249 intConfigErr The interrupt configuration is incorrect given the capabilities of the
computer or device.
-10250 dupIntErr The interrupt levels for two or more devices are the same.
-10251 dmaConfigErr The DMA configuration is incorrect given the capabilities of the
computer/DMA controller or device.
-10252 dupDMAErr The DMA channels for two or more devices are the same.
-10253 switchlessBoardErr NI-DAQ was unable to find one or more switchless boards you
have configured using WDAQCONF.
-10254 DAQCardConfigErr Cannot configure the DAQCard because: 1) The correct
version of card and socket services software is not installed. 2) The card in the
PCMCIA socket is not a DAQCard. 3) The base address and/or interrupt level
requested are not available according to the card and socket services resource
manager. Try different settings or use AutoAssign in the NIDAQ configuration
utility.
(continues)

© National Instruments Corporation

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Chapter 10

Table 10-5. Easy I/O for DAQ Error Codes (Continued)
-10340 noConnectErr No RTSI signal/line is connected, or the specified signal and the
specified line are not connected.
-10341 badConnectErr The RTSI signal/line cannot be connected as specified.
-10342 multConnectErr The specified RTSI signal is already being driven by a RTSI line,
or the specified RTSI line is already being driven by a RTSI signal.
-10343 SCXIConfigErr The specified SCXI configuration parameters are invalid, or the
function cannot be executed given the current SCXI configuration.
-10360 DSPInitErr The DSP driver was unable to load the kernel for its operating system.
-10370 badScanListErr The scan list is invalid. This error can result if, for example, you
mix AMUX-64T channels and onboard channels, or if you scan multiplexed SCXI
channels out of order.
-10400 userOwnedRsrcErr The specified resource is owned by the user and cannot be
accessed or modified by the driver.
-10401 unknownDeviceErr The specified device is not a National Instruments product, or
the driver does not work with the device (for example, the driver was released before
the features of the device existed).
-10402 deviceNotFoundErr No device is located in the specified slot or at the specified
address.
-10403 deviceSupportErr The requested action does not work with specified device (the
driver recognizes the device, but the action is inappropriate for the device).
-10404 noLineAvailErr No line is available.
-10405 noChanAvailErr No channel is available.
-10406 noGroupAvailErr No group is available.
-10407 lineBusyErr The specified line is in use.
-10408 chanBusyErr The specified channel is in use.
-10409 groupBusyErr The specified group is in use.
-10410 relatedLCGBusyErr A related line, channel, or group is in use; if the driver
configures the specified line, channel, or group, the configuration, data, or
handshaking lines for the related line, channel, or group will be disturbed.
-10411 counterBusyErr The specified counter is in use.
-10412 noGroupAssignErr No group is assigned, or the specified line or channel cannot be
assigned to a group.
-10413 groupAssignErr A group is already assigned, or the specified line or channel is
already assigned to a group.
(continues)

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Table 10-5. Easy I/O for DAQ Error Codes (Continued)
-10414 reservedPinErr Selected signal indicates a pin reserved by NI-DAQ. You cannot
configure this pin yourself.
-10440 sysOwnedRsrcErr The specified resource is owned by the driver and cannot be
accessed or modified by the user.
-10441 memConfigErr No memory is configured to work with the current data transfer
mode, or the configured memory does not work with the current data transfer mode.
(If block transfers are in use, the memory must be capable of performing block
transfers.)
-10442 memDisabledErr The specified memory is disabled or is unavailable given the
current addressing mode.
-10443 memAlignmentErr The transfer buffer is not aligned properly for the current data
transfer mode. For example, the memory buffer is at an odd address, is not aligned to
a 32-bit boundary, is not aligned to a 512-bit boundary, and so on. Alternatively, the
driver is unable to align the buffer because the buffer is too small.
-10444 memFullErr No more system memory is available on the heap, or no more memory
is available on the device.
-10445 memLockErr The transfer buffer cannot be locked into physical memory.
-10446 memPageErr The transfer buffer contains a page break; system resources may
require reprogramming when the page break is encountered.
-10447 memPageLockErr The operating environment is unable to grant a page lock.
-10448 stackMemErr The driver is unable to continue parsing a string input due to stack
limitations.
-10449 cacheMemErr A cache-related error occurred, or caching does not work in the
current mode.
-10450 physicalMemErr A hardware error occurred in physical memory, or no memory is
located at the specified address.
-10451 virtualMemErr The driver is unable to make the transfer buffer contiguous in virtual
memory and therefore cannot lock the buffer into physical memory; thus, you cannot
use the buffer for DMA transfers.
-10452 noIntAvailErr No interrupt level is available for use.
-10453 intInUseErr The specified interrupt level is already in use by another device.
-10454 noDMACErr No DMA controller is available in the system.
-10455 noDMAAvailErr No DMA channel is available for use.
-10456 DMAInUseErr The specified DMA channel is already in use by another device.
(continues)

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Table 10-5. Easy I/O for DAQ Error Codes (Continued)
-10457 badDMAGroupErr DMA cannot be configured for the specified group because it is
too small, too large, or misaligned. Consult the user manual for the device in question
to determine group ramifications with respect to DMA.
-10459 DLLInterfaceErr The DLL could not be called due to an interface error.
-10460 interfaceInteractionErr You have attempted to mix LabVIEW 2.2 VIs and
LabVIEW 3.0 VIs. You may run an application consisting only of 2.2 VIs, then run
the 2.2 Board Reset VI, before you can run any 3.0 VIs. You may run an application
consisting of only 3.0 VIs, then run the 3.0 Device Reset VI, before you can run any
2.2 VIs.
-10560 invalidDSPhandleErr The DSP handle input to the VI is not a valid handle.
-10600 noSetupErr No setup operation has been performed for the specified resources.
-10601 multSetupErr The specified resources have already been configured by a setup
operation.
-10602 noWriteErr No output data has been written into the transfer buffer.
-10603 groupWriteErr The output data associated with a group must be for a single channel
or must be for consecutive channels.
-10604 activeWriteErr Once data generation has started, only the transfer buffers originally
written to can be updated. If DMA is active and a single transfer buffer contains
interleaved channel data, all output channels currently using the DMA channel will
require new data.
-10605 endWriteErr No data was written to the transfer buffer because the final data block
has already been loaded.
-10606 notArmedErr The specified resource is not armed.
-10607 armedErr The specified resource is already armed.
-10608 noTransferInProgErr No transfer is in progress for the specified resource.
-10609 transferInProgErr A transfer is already in progress for the specified resource.
-10610 transferPauseErr A single output channel in a group cannot be paused if the output
data for the group is interleaved.
-10611 badDirOnSomeLinesErr Some of the lines in the specified channel are not
configured for the transfer direction specified. For a write transfer, some lines were
configured for input. For a read transfer, some lines were configured for output.
-10612 badLineDirErr The specified line does not support the specified transfer direction.
-10613 badChanDirErr The specified channel does not support the specified transfer
direction.
(continues)

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Table 10-5. Easy I/O for DAQ Error Codes (Continued)
-10614 badGroupDirErr The specified group does not support the specified transfer
direction.
-10615 masterClkErr The clock configuration for the clock master is invalid.
-10616 slaveClkErr The clock configuration for the clock slave is invalid.
-10617 noClkSrcErr No source signal has been assigned to the clock resource.
-10618 badClkSrcErr The specified source signal cannot be assigned to the clock resource.
-10619 multClkSrcErr A source signal has already been assigned to the clock resource.
-10620 noTrigErr No trigger signal has been assigned to the trigger resource.
-10621 badTrigErr The specified trigger signal cannot be assigned to the trigger resource.
-10622 preTrigErr The pretrigger mode is not supported or is not available in the current
configuration, or no pretrigger source has been assigned.
-10623 postTrigErr No posttrigger source has been assigned.
-10624 delayTrigErr The delayed trigger mode is not supported or is not available in the
current configuration, or no delay source has been assigned.
-10625 masterTrigErr The trigger configuration for the trigger master is invalid.
-10626 slaveTrigErr The trigger configuration for the trigger slave is invalid.
-10627 noTrigDrvErr No signal has been assigned to the trigger resource.
-10628 multTrigDrvErr A signal has already been assigned to the trigger resource.
-10629 invalidOpModeErr The specified operating mode is invalid, or the resources have
not been configured for the specified operating mode.
-10630 invalidReadErr An attempt was made to read 0 bytes from the transfer buffer, or an
attempt was made to read past the end of the transfer buffer.
-10631 noInfiniteModeErr Continuous input or output transfers are invalid in the current
operating mode.
-10632 someInputsIgnoredErr Certain inputs were ignored because they are not relevant in
the current operating mode.
-10633 invalidRegenModeErr This device does not support the specified analog output
regeneration mode.
-10680 badChanGainErr All channels must have an identical setting for this device.
-10681 badChanRangeErr All channels of this device must have the same range.
-10682 badChanPolarityErr All channels of this device must have the same polarity.
-10683 badChanCouplingErr All channels of this device must have the same coupling.
(continues)

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Table 10-5. Easy I/O for DAQ Error Codes (Continued)
-10684 badChanInputModeErr All channels of this device must have the same input
range.
-10685 clkExceedsBrdsMaxConvRate The clock rate selected exceeds the recommended
maximum rate for this device.
-10686 scanListInvalidErr A configuration change has invalidated the scan list.
-10687 bufferInvalidErr A configuration change has invalidated the allocated buffer.
-10688 noTrigEnabledErr The total number of scans and pretrigger scans implies that a
trigger start is intended, but no trigger is enabled.
-10689 digitalTrigBErr Digital trigger B is illegal for the total scans and pretrigger scans
specified.
-10690 digitalTrigAandBErr With this device, you cannot enable digital triggers A and B
at the same time.
-10691 extConvRestrictionErr With this device, you cannot use an external sample clock
with an external scan clock, start trigger, or stop trigger.
-10692 chanClockDisabledErr Cannot start the acquisition because the channel clock is
disabled.
-10693 extScanClockErr Cannot use an external scan clock when performing a single scan
of a single channel.
-10694 unsafeSamplingFreqErr The sampling frequency exceeds the safe maximum rate
for the ADC, gains, and filters you are using.
-10695 DMAnotAllowedErr You must use interrupts. DMA does not work.
-10696 multiRateModeErr Multi-rate scanning can not be used with AMUX-64, SCXI, or
pre-triggered acquisitions.
-10697 rateNotSupportedErr NI-DAQ was unable to convert your timebase/interval pair to
match the actual hardware capabilities of the specified board.
-10698 timebaseConflictErr You cannot use this combination of scan and sample clock
timebases for the specified board.
-10699 polarityConflictErr You cannot use this combination of scan and sample clock
source polarities for this operation, for the specified board.
-10700 signalConflictErr You cannot use this combination of scan and convert clock signal
sources for this operation, for the specified board.
-10740 SCXITrackHoldErr A signal has already been assigned to the SCXI track-and-hold
trigger line, or a control call was inappropriate because the specified module is not
configured for one-channel operation.
(continues)

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Table 10-5. Easy I/O for DAQ Error Codes (Continued)
-10780 sc2040InputModeErr When you have an SC2040 attached to your device, all analog
input channels must be configured for differential input mode.
-10800 timeOutErr The operation could not complete within the time limit.
-10801 calibrationErr An error occurred during the calibration process.
-10802 dataNotAvailErr The requested amount of data has not yet been acquired, or the
acquisition has completed and no more data is available to read.
-10803 transferStoppedErr The transfer has been stopped to prevent regeneration of output
data.
-10804 earlyStopErr The transfer stopped prior to reaching the end of the transfer buffer.
-10805 overRunErr The clock source for the input transfer is faster than the maximum
input-clock rate; the integrity of the data has been compromised. Alternatively, the
clock source for the output transfer is faster than the maximum output-clock rate; a
data point was generated more than once because the update occurred before new
data was available.
-10806 noTrigFoundErr No trigger value was found in the input transfer buffer.
-10807 earlyTrigErr The trigger occurred before sufficient pretrigger data was acquired.
-10809 gateSignalErr Attempted to start a pulse width measurement with the pulse in the
active state.
-10840 softwareErr The contents or the location of the driver file was changed between
accesses to the driver.
-10841 firmwareErr The firmware does not support the specified operation, or the firmware
operation could not complete due to a data-integrity problem.
-10842 hardwareErr The hardware is not responding to the specified operation, or the
response from the hardware is not consistent with the functionality of the hardware.
-10843 underFlowErr The update rate exceeds your system's capacity to supply data to the
output channel.
-10844 underWriteErr At the time of the update for the device-resident memory,
insufficient data was present in the output transfer buffer to complete the update.
-10845 overFlowErr At the time of the update clock for the input channel, the deviceresident memory was unable to accept additional data—one or more data points may
have been lost.
-10846 overWriteErr New data was written into the input transfer buffer before the old data
was retrieved.
-10847 dmaChainingErr New buffer information was not available at the time of the DMA
chaining interrupt; DMA transfers will terminate at the end of the currently active
transfer buffer.
(continues)
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Table 10-5. Easy I/O for DAQ Error Codes (Continued)
-10848 noDMACountAvailErr The driver could not obtain a valid reading from the
transfer-count register in the DMA controller.
-10849 openFileErr Unable to open a file.
-10850 closeFileErr Unable to close a file.
-10851 fileSeekErr Unable to seek within a file.
-10852 readFileErr Unable to read from a file.
-10853 writeFileErr Unable to write to a file.
-10854 miscFileErr An error occurred accessing a file.
-10880 updateRateChangeErr A change to the update rate is not possible at this time
because: 1) When waveform generation is in progress, you cannot change the interval
timebase. 2) When you make several changes in a row, you must wait long enough
for each change to take effect before you request further changes.
-10920 gpctrDataLossErr One or more data points may have been lost during buffered
GPCTR operations due to speed limitations of your system.

LabWindows/CVI Standard Libraries

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© National Instruments Corporation

Appendix A
Customer Communication
For your convenience, this appendix contains forms to help you gather the information necessary
to help us solve technical problems you might have as well as a form you can use to comment on
the product documentation. Filling out a copy of the Technical Support Form before contacting
National Instruments helps us help you better and faster.
National Instruments provides comprehensive technical assistance around the world. In the U.S.
and Canada, applications engineers are available Monday through Friday from 8:00 a.m. to
6:00 p.m. (central time). In other countries, contact the nearest branch office. You may fax
questions to us at any time.

Electronic Services
Bulletin Board Support
National Instruments has BBS and FTP sites dedicated for 24-hour support with a collection of
files and documents to answer most common customer questions. From these sites, you can also
download the latest instrument drivers, updates, and example programs. For recorded
instructions on how to use the bulletin board and FTP services and for BBS automated
information, call (512) 795-6990. You can access these services at:
•

United States: (512) 794-5422 or (800) 327-3077
Up to 14,400 baud, 8 data bits, 1 stop bit, no parity

•

United Kingdom: 01635 551422
Up to 9,600 baud, 8 data bits, 1 stop bit, no parity

•

France: 1 48 65 15 59
Up to 9,600 baud, 8 data bits, 1 stop bit, no parity

FaxBack Support
FaxBack is a 24-hour information retrieval system containing a library of documents on a wide
range of technical information. You can access FaxBack from a touch-tone telephone at the
following number: (512) 418-1111.

© National Instruments Corporation

A-1

LabWindows/CVI Standard Libraries

Customer Communication

Appendix A

FTP Support
To access our FTP site, log on to our Internet host, ftp.natinst.com, as anonymous and use your
Internet address, such as joesmith@anywhere.com, as your password. The support files and
documents are located in the /support directories.

E-Mail Support (currently U.S. only)
You can submit technical support questions to the appropriate applications engineering team through email at the Internet addresses listed below. Remember to include your name, address, and phone number
so we can contact you with solutions and suggestions.
GPIB:
DAQ:
VXI:
LabVIEW:
LabWindows:
HiQ:
VISA:
Lookout:

gpib.support@natinst.com
daq.support@natinst.com
vxi.support@natinst.com
lv.support@natinst.com
lw.support@natinst.com
hiq.support@natinst.com
visa.support@natinst.com
lookout.support@natinst.com

Fax and Telephone Support
National Instruments has branch offices all over the world. Use the list below to find the technical
support number for your country. If there is no National Instruments office in your country, contact the
source from which you purchased your software to obtain support.

Telephone
Australia
Austria
Belgium
Canada (Ontario)
Canada (Quebec)
Denmark
Finland
France
Germany
Hong Kong
Italy
Japan
Korea
Mexico
Netherlands
Norway
Singapore
Spain
Sweden
Switzerland
Taiwan
U.K.

Fax

03 9 879 9422
0662 45 79 90 0
02 757 00 20
519 622 9310
514 694 8521
45 76 26 00
90 527 2321
1 48 14 24 24
089 741 31 30
2645 3186
02 413091
03 5472 2970
02 596 7456
95 800 010 0793
0348 433466
32 84 84 00
2265886
91 640 0085
08 730 49 70
056 200 51 51
02 377 1200
01635 523545

LabWindows/CVI Standard Libraries

03 9 879 9179
0662 45 79 90 19
02 757 03 11
514 694 4399
45 76 26 02
90 502 2930
1 48 14 24 14
089 714 60 35
2686 8505
02 41309215
03 5472 2977
02 596 7455
5 520 3282
0348 430673
32 84 86 00
2265887
91 640 0533
08 730 43 70
056 200 51 55
02 737 4644
01635 523154

A-2

© National Instruments Corporation

Technical Support Form
Photocopy this form and update it each time you make changes to your software or hardware, and use the completed
copy of this form as a reference for your current configuration. Completing this form accurately before contacting
National Instruments for technical support helps our applications engineers answer your questions more efficiently.
If you are using any National Instruments hardware or software products related to this problem, include the
configuration forms from their user manuals. Include additional pages if necessary.
Name _______________________________________________________________________________________
Company ____________________________________________________________________________________
Address _____________________________________________________________________________________
____________________________________________________________________________________________
Fax

(

)

Phone

Computer brand

Model

Mouse

MHz
yes

Hard disk capacity

no

RAM

)
Processor

Operating system: Windows 3.1, Windows for Workgroups 3.11,
Windows 95, other (include version number)
Clock Speed

(

MB

Windows NT 3.1,

Display adapter

Other adapters installed
MB

Brand

Instruments used
National Instruments hardware product model

Revision

Configuration
National Instruments software product
Configuration
The problem is

List any error messages

The following steps will reproduce the problem

Windows NT 3.5,

Version

Hardware and Software Configuration Form
Record the settings and revisions of your hardware and software on the line to the right of each item. Complete a
new copy of this form each time you revise your software or hardware configuration, and use this form as a
reference for your current configuration. When you complete this form accurately before contacting National
Instruments for technical support, our applications engineers can answer your questions more efficiently.

National Instruments Products
Data Acquisition Hardware Revision ______________________________________________________________
Interrupt Level of Hardware _____________________________________________________________________
DMA Channels of Hardware ____________________________________________________________________
Base I/O Address of Hardware ___________________________________________________________________
NI-DAQ, LabVIEW, or
LabWindows Version __________________________________________________________________________

Other Products
Computer Make and Model _____________________________________________________________________
Microprocessor _______________________________________________________________________________
Clock Frequency ______________________________________________________________________________
Type of Video Board Installed ___________________________________________________________________
Operating System _____________________________________________________________________________
Operating System Version ______________________________________________________________________
Operating System Mode ________________________________________________________________________
Programming Language ________________________________________________________________________
Programming Language Version _________________________________________________________________
Other Boards in System ________________________________________________________________________
Base I/O Address of Other Boards ________________________________________________________________
DMA Channels of Other Boards _________________________________________________________________
Interrupt Level of Other Boards __________________________________________________________________

Documentation Comment Form
National Instruments encourages you to comment on the documentation supplied with our products. This
information helps us provide quality products to meet your needs.
Title:

LabWindows®/CVI Standard Libraries Reference Manual

Edition Date:

July 1996

Part Number:

320682C-01

Please comment on the completeness, clarity, and organization of the manual.
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Mail to: Technical Publications
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Fax to: Technical Publications
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Glossary
Prefix

Meaning

Value

n-

nano-

10

µ-

micro-

10

m-

milli-

10

k-

kilo-

10

M-

mega-

10

-9
-6
-3
3
6

Numbers/Symbols
1D

One-dimensional.

2D

Two-dimensional.

A
A

Analog input.

A/D

Analog-to-digital.

AC

Alternating current.

ADC A/D
converter

An electronic device, often an integrated circuit, that converts an analog
voltage to a digital number.

ADC resolution

The resolution of the ADC, which is measured in bits. An ADC with
16 bits has a higher resolution, and thus a higher degree of accuracy, than a
12-bit ADC.

analog trigger

A trigger that occurs at a user-selected point on an incoming analog signal.
Triggering can be set to occur at a specific level on either an increasing or a
decreasing signal (positive or negative slope). Analog triggering can be
implemented either in software or in hardware. When implemented in
software, all data is collected, transferred into system memory, and
analyzed for the trigger condition. When analog triggering is implemented

© National Instruments Corporation

G-1

LabWindows/CVI Standard Libraries

Glossary

in hardware, no data is transferred to system memory until the trigger
condition has occurred.
ANSI

American National Standards Institute.

AO

Analog output.

asynchronous

(1) Hardware—A property of an event that occurs at an arbitrary time,
without synchronization to a reference clock.
(2) Software—A property of a function that begins an operation and
returns prior to the completion or termination of the operation.

automatic serial

A feature in which serial polls are executed automatically by the GPIB
polling driver whenever a device asserts the SRQ line.

B
B

Bytes.

background
acquisition

Data is acquired by a DAQ system while another program or processing
routine is running without apparent interruption.

bipolar

A signal range that includes both positive and negative values (for
example, -5 V to +5 V).

block-mode

A high-speed data transfer in which the address of the data is sent followed
by a specified number of back-to-back data words.

C
CodeBuilder

The LabWindows/CVI feature that creates code based on a .uir file to
connect your GUI to the rest of your program. This code is complete and
can be compiled and run as soon as it is created.

cold-junction
compensation

A method of compensating for inaccuracies in thermocouple circuits.

conversion time

The time required, in an analog input or output system, from the moment a
channel is interrogated (such as with a read instruction) to the moment that
accurate data is available.

counter/timer

A circuit that counts external pulses or clock pulses (timing).

coupling

The manner in which a signal is connected from one location to another.

LabWindows/CVI Standard Libraries

G-2

© National Instruments Corporation

Glossary

D
D/A

Digital-to-analog.

DAC D/A
converter

An electronic device, often an integrated circuit, that converts a digital
number into a corresponding analog voltage or current.

Data acquisition

(1) Collecting and measuring electrical signals from sensors, transducers,
and test probes or fixtures and inputting them to a computer for processing.
(2) Collecting and measuring the same kinds of electrical signals with A/D
and/or DIO boards plugged into a PC, and possibly generating control
signals with D/A and/or DIO boards in the same PC.

DC

Direct current.

device

Device is used to refer to a DAQ device inside your computer or attached
directly to your computer via a parallel port. Plug-in boards, PCMCIA
cards, and devices such as the DAQPad-1200, which connects to your
computer parallel port, are all examples of DAQ devices. SCXI modules
are distinct from devices, with the exception of the SCXI-1200, which is a
hybrid.

differential input

An analog input consisting of two terminals, both of which are isolated
from computer ground, whose difference is measured.

digital port

See port.

DIO

Digital I/O.

E
external trigger

A voltage pulse from an external source that triggers an event such as A/D
conversion.

F
FIFO

A first-in first-out memory buffer; the first data stored is the first data sent
to the acceptor.

format string

A mini-program that instructs the formatting and scanning functions how
to transform the input arguments to the output arguments. For conciseness,
format strings are constructed using single-character codes.

© National Instruments Corporation

G-3

LabWindows/CVI Standard Libraries

Glossary

G
G gain

The factor by which a signal is amplified, sometimes expressed in decibels.

gender

Refers to cable connector types. A male connector is one with protruding
pins, like a lamp plug. A female connector has holes, like an outlet.

gender changer

A small device that can be attached to serial cable connectors or PC
sockets, among others, to convert a female connector into a male, or a male
connector into a female.

GPIB

General Purpose Interface Bus is the common name for the
communications interface system defined in ANSI/IEEE Standards
488.1-1987 and 488.2-1992.

group

A collection of digital ports, combined to form a larger entity for digital
input and/or output.

H
handshaking

Prevents overflow of the input queue that occurs when the receiver is
unable to empty its input queue as quickly as the sender is able to fill it.
The RS-232 Library has two types of handshaking–software handshaking,
and hardware handshaking. You should enable one or the other if you want
to ensure that your application program synchronizes its data transfers with
other serial devices that perform handshaking.

Hz

Hertz.

I
I/O

Input/output.

ID

Identification.

IEEE

Institute of Electrical and Electronics Engineers.

in.

Inches.

Instrument Library

A LabWindows/CVI library that contains instrument drivers.

interrupt

A computer signal indicating that the CPU should suspend its current task
to service a designated activity.

LabWindows/CVI Standard Libraries

G-4

© National Instruments Corporation

Glossary

K
KB

Kilobytes of memory.

kS

1,000 samples.

ksamples

1,000 samples.

L
LSB

Least significant bit.

M
manual scaling

Where SetAxRange is called to explicitly set the maximum and
minimum X and Y values.

MB

Megabytes of memory.

MIO

Multifunction I/O.

ms

Milliseconds.

mux

Multiplexer; a switching device with multiple inputs that sequentially
connects each of its inputs to its output, typically at high speeds, in order to
measure several signals with a single analog input channel.

N
NI-488 functions

National Instruments functions you use to communicate with GPIB devices
built according to the ANSI/IEEE Standards 488.1-1987 and 488.2-1992.

NI-488.2 routines

National Instruments routines you use to communicate with GPIB devices
built according to the ANSI/IEEE Standard 488.2-1992.

P
port

A digital port, consisting of four or eight lines of digital input and/or
output.

postriggering

The technique used on a DAQ board to acquire a programmed number of
samples after trigger conditions are met.

© National Instruments Corporation

G-5

LabWindows/CVI Standard Libraries

Glossary

pretriggering

The technique used on a DAQ board to keep a continuous buffer filled with
data, so that when the trigger conditions are met, the sample includes the
data leading up to the trigger condition.

pts

Points.

R
resolution

The smallest signal increment that can be detected by a measurement
system. Resolution can be expressed in bits, in proportions, or in percent of
full scale. For example, a system has 12-bit resolution, one part in
4,096 resolution, and 0.0244 percent of full scale.

RTD

Resistance temperature detector. A metallic probe that measures
temperature based upon its coefficient of resistivity.

S
s

Seconds.

S/s

Samples per second; used to express the rate at which a DAQ board
samples an analog signal.

Sample-and-Hold
(S/H)

A circuit that acquires and stores an analog voltage on a capacitor for a
short period of time.

SCXI

Signal Conditioning eXtensions for Instrumentation; the National
Instruments product line for conditioning low-level signals within an
external chassis near sensors so only high-level signals are sent to DAQ
boards in the noisy PC environment.

self-calibrating

A property of a DAQ board that has an extremely stable onboard reference
and calibrates its own A/D and D/A circuits without manual adjustments
by the user.

Single-Ended (SE)
Inputs

An analog input that is measured with respect to a common ground.

software trigger

A programmed event that triggers an event such as data acquisition.

standard libraries

The LabWindows/CVI Analysis, ANSI C, DDE, Formatting and I/O, GPIB
and GPIB-488.2, RS-232, TCP, and Utility libraries.

STC System

Timing Controller.

synchronous

(1) Hardware—Property of an event that is synchronized to a reference clock
(2) Software—Property of a function that begins an operation and returns
only when the operation is complete.

LabWindows/CVI Standard Libraries

G-6

© National Instruments Corporation

Glossary

T
TC

Terminal count.

throughput rate

The data, measured in bytes/s, for a given continuous operation, calculated
to include software overhead. Throughput Rate = Transfer Rate - Software
Overhead Factor.

transfer rate

The rate, measured in bytes/s, at which data is moved from source to
destination after software initialization and set up operations; the maximum
rate at which the hardware can operate.

U
unipolar

A signal range that is always positive (for example, 0 to +10 V).

V
V

Volts.

VDC

Volts direct current.

X
Xmodem functions

Allow you to transfer files using a data transfer protocol. The protocol uses
a generally accepted technique for performing serial file transfers with
error-checking. Files are sent in packets that contain data from the files
plus error-checking and synchronization information.

© National Instruments Corporation

G-7

LabWindows/CVI Standard Libraries

Index
Numbers/Symbols
1D array functions. See one-dimensional
array operation functions.
1D complex operation functions. See onedimensional complex operation functions.
2D array functions. See two-dimensional
array operation functions.
* (asterisks) in format specifiers
formatting functions, 2-39
scanning functions, 2-48

A
Abs1D function, 3-4 to 3-5
accessing physical memory. See physical
memory access functions.
accessing window properties. See window
properties, accessing.
Add1D function, 3-5
Add2D function, 3-5 to 3-6
AdviseDDEDataReady function, 6-6 to 6-8
AIAcquireTriggeredWaveforms function,
10-8 to 10-13
AIAcquireWaveforms function, 10-13
to 10-14
AICheckAcquisition function, 10-15
AIClearAcquisition function, 10-15
AIReadAcquisition function, 10-16 to 10-17
AISampleChannel function, 10-17 to 10-18
AISampleChannels function, 10-18
AIStartAcquisition function, 10-19
analog input functions. See also Easy I/O for
DAQ Library.
AIAcquireTriggeredWaveforms, 10-8
to 10-13
AIAcquireWaveforms, 10-33 to 10-34
AISampleChannel, 10-17 to 10-18
AISampleChannels, 10-18
Channel String, 10-4 to 10-5

© National Instruments Corporation

I-1

analog output functions. See also Easy I/O
for DAQ Library.
AOClearWaveforms, 10-20
AOGenerateWaveforms, 10-21 to 10-22
AOUpdateChannel, 10-22 to 10-23
AOUpdateChannels, 10-23 to 10-24
Channel String, 10-7
Analysis Library functions
error conditions, 3-37
function panels
classes and subclasses, 3-3
function tree (table), 3-1 to 3-2
hints for using, 3-3 to 3-4
function reference
Abs1D, 3-4 to 3-5
Add1D, 3-5
Add2D, 3-5 to 3-6
Clear1D, 3-6 to 3-7
Copy1D, 3-7
CxAdd, 3-7 to 3-8
CxAdd1D, 3-8 to 3-9
CxDiv, 3-9
CxDiv1D, 3-10
CxLinEv1D, 3-11
CxMul, 3-12
CxMul1D, 3-12 to 3-13
CxRecip, 3-13 to 3-14
CxSub, 3-14
CxSub1D, 3-15
Determinant, 3-16
Div1D, 3-16 to 3-17
Div2D, 3-17 to 3-18
DotProduct, 3-18
GetAnalysisErrorString, 3-19
Histogram, 3-19 to 3-20
InvMatrix, 3-20 to 3-21
LinEv1D, 3-21
LinEv2D, 3-22
MatrixMul, 3-23
MaxMin1D, 3-24

LabWindows/CVI Standard Libraries

Index

MaxMin2D, 3-24 to 3-25
Mean, 3-25 to 3-26
Mul1D, 3-26 to 3-27
Mul2D, 3-27
Neg1D, 3-28
Set1D, 3-28
Sort, 3-29
StdDev, 3-29 to 3-30
Sub1D, 3-30 to 3-31
Sub2D, 3-31
Subset1D, 3-32
ToPolar, 3-32 to 3-33
ToPolar1D, 3-33 to 3-34
ToRect, 3-34 to 3-35
ToRect1D, 3-35
Transpose, 3-36
overview, 3-1
reporting analysis errors, 3-4
ANSI C Library
C locale, 1-2 to 1-5
information values (table), 1-3
LC_COLLATE, 1-5
LC_CTYPE, 1-4 to 1-5
LC_MONETARY, 1-4
LC_NUMERIC, 1-4
LC_TIME, 1-5
character processing, 1-5
classes (table), 1-1 to 1-2
control functions, 1-7 to 1-9
errno set by file I/O functions, 1-6
fdopen function, 1-9 to 1-10
input/output facilities, 1-6
low-level I/O functions, 1-2
mathematical functions, 1-6
standard language additions, 1-2 to 1-5
string processing, 1-5
time and date functions, 1-6 to 1-7
ANSI C macros, 1-2
AOClearWaveforms function, 10-20
AOGenerateWaveforms function, 10-21
to 10-22
AOUpdateChannel function, 10-22 to 10-23
AOUpdateChannels function, 10-23
to 10-24
array operation functions
Abs1D, 3-4 to 3-5
LabWindows/CVI Standard Libraries

I-2

Add1D, 3-5
Add2D, 3-5 to 3-6
Div1D, 3-16 to 3-17
Div2D, 3-17 to 3-18
LinEv1D, 3-21
LinEv2D, 3-22
MaxMin1D, 3-24
MaxMin2D, 3-24 to 3-25
Mul1D, 3-26 to 3-27
Mul2D, 3-27
Neg1D, 3-28
Sub1D, 3-30 to 3-31
Sub2D, 3-31
Subset1D, 3-32
array utility functions
Clear1D, 3-6 to 3-7
Copy1D, 3-7
Set1D, 3-28
ArrayToFile function, 2-4 to 2-6
asterisks (*) in format specifiers
formatting functions, 2-39
scanning functions, 2-48
asynchronous acquisition functions
AICheckAcquisition, 10-15
AIClearAcquisition, 10-15
AIReadAcquisition, 10-16 to 10-17
AIStartAcquisition, 10-19
PlotLastAIWaveformsPopup, 10-47
asynchronous callbacks
notification of SRQ and other GPIB
events, 4-12
restrictions with ibNotify function, 4-20
automatic serial polling
compatibility, 4-8
hardware interrupts, 4-8 to 4-9
purpose and use, 4-7 to 4-8
RQS events
ibInstallCallback function, 4-17
ibNotify function, 4-19
SRQI events
ibInstallCallback function, 4-17
ibNotify function, 4-19

© National Instruments Corporation

Index

B
Beep function, 8-5
board control functions, GPIB, 4-7
board control functions, GPIB Library, 4-3
break on library error functions
DisableBreakOnLibraryErrors, 8-11
to 8-12
EnableBreakOnLibraryErrors, 8-15
GetBreakOnLibraryErrors, 8-17
GetBreakOnProtectionErrors, 8-18
SetBreakOnLibraryErrors, 8-63 to 8-64
SetBreakOnProtectionErrors, 8-64
to 8-65
Breakpoint function, 8-6
BroadcastDDEDataReady function, 6-8
to 6-9
bus control functions, GPIB Library, 4-3
byte count variable (ibcntl), 4-6

C
C locale, 1-2 to 1-5
information values (table), 1-3
LC_COLLATE, 1-5
LC_CTYPE, 1-4 to 1-5
LC_MONETARY, 1-4
LC_NUMERIC, 1-4
LC_TIME, 1-5
cables. See RS-232 cables.
callback functions
DDE Library functions, 6-2 to 6-4
DDE transaction types (table), 6-4
example using Excel, 6-5 to 6-6
parameter prototypes (table), 6-3
GPIB/GPIB-488.2 Libraries
function tree, 4-3
ibInstallCallback, 4-12, 4-14 to 4-17
ibNotify, 4-12, 4-17 to 4-20
Windows NT and Windows 95
asynchronous callbacks, 4-12
driver version requirements, 4-12
ibInstallCallback, 4-14 to 4-17
ibNotify function, 4-17 to 4-20
synchronous callbacks, 4-12

© National Instruments Corporation

I-3

RS-232 Library
function tree, 5-2
InstallComCallback, 5-22 to 5-25
TCP Library functions
overview, 7-2 to 7-3
TCP transaction types (table), 7-3
X Property Library functions
InstallXPropertyCallback, 9-4, 9-25
to 9-27
overview, 9-4
UninstallXPropertyCallback, 9-4, 9-33
character processing, ANSI C, 1-5
classes, ANSI C Library, 1-1 to 1-2
clear functions, GPIB-488.2 Library, 4-3
Clear1D function, 3-6 to 3-7
ClientDDEExecute function, 6-10
ClientDDERead function, 6-10 to 6-11
ClientDDEWrite function, 6-12 to 6-13
clients and servers
DDE Library functions, 6-2
TCP Library functions, 7-2
ClientTCPRead function, 7-3 to 7-4
ClientTCPWrite function, 7-4 to 7-5
close functions
GPIB and GPIB-488.2 Libraries, 4-2
RS-232 Library, 5-1
CloseCom function, 5-8 to 5-9
CloseCVIRTE function, 8-6
CloseDev function, 4-6 to 4-7, 4-13
CloseFile function, 2-7
CloseInstrDevs function, 4-14
Cls function, 8-7
ComBreak function, 5-9
ComFromFile function, 5-3, 5-9 to 5-10
communications functions. See RS-232
Library functions.
CompareBytes function, 2-7 to 2-8
CompareStrings function, 2-8 to 2-9
complex operation functions
CxAdd, 3-7 to 3-8
CxAdd1D, 3-8 to 3-9
CxDiv, 3-9
CxDiv1D, 3-10
CxLinEv1D, 3-11
CxMul, 3-12
CxMul1D, 3-12 to 3-13
LabWindows/CVI Standard Libraries

Index

CxRecip, 3-13 to 3-14
CxSub, 3-14
CxSub1D, 3-15
ToPolar, 3-32 to 3-33
ToPolar1D, 3-33 to 3-34
ToRect, 3-34 to 3-35
ToRect1D, 3-35
ComRd function, 5-11
ComRdByte function, 5-12
ComRdTerm function, 5-12 to 5-13
ComSetEscape function, 5-14 to 5-15
ComToFile function, 5-3, 5-15 to 5-16
ComWrt function, 5-16 to 5-17
ComWrtByte function, 5-17 to 5-18
configuration functions, GPIB Library, 4-2
ConnectToDDEServer function, 6-2, 6-13
to 6-15
ConnectToTCPServer function, 7-5 to 7-7
ConnectToXDisplay function, 9-3, 9-7
to 9-9
ContinuousPulseGenConfig, 10-24 to 10-26
control functions
ANSI C library, 1-7 to 1-9
error codes, 1-8
RS-232 Library
ComBreak, 5-9
ComSetEscape, 5-14 to 5-15
FlushInQ, 5-18
SetComTime, 5-29
SetCTSMode, 5-7, 5-30
SetXMode, 5-6, 5-31
Copy1D function, 3-7
CopyBytes function, 2-9 to 2-10
CopyFile function, 8-7 to 8-8
CopyString function, 2-10
Count control, GPIB, 4-6
Count Variables (ibcnt, ibcntl), 4-6, 4-10
CounterEventOrTimeConfig function, 10-26
to 10-29
CounterMeasureFrequency function, 10-29
to 10-32
CounterRead function, 10-32 to 10-33
CounterStart function, 10-33
CounterStop function, 10-34
counter/timer functions. See also Easy I/O
for DAQ Library.
LabWindows/CVI Standard Libraries

I-4

ContinuousPulseGenConfig, 10-24
to 10-26
CounterEventOrTimeConfig, 10-26
to 10-29
CounterMeasureFrequency, 10-29 to
10-32
CounterRead, 10-32 to 10-33
CounterStart, 10-33
CounterStop, 10-34
DelayedPulseGenConfig, 10-34 to 10-36
FrequencyDividerConfig, 10-37 to 10-39
ICounterControl, 10-45 to 10-47
PulseWidthOrPeriodMeasConfig, 10-48
to 10-49
valid counters (table), 10-7
CreateXProperty function, 9-3, 9-9 to 9-10
CreateXPropType function, 9-3, 9-10
to 9-12
customer communication, xx, Appendix-1
CVILowLevelSupportDriverLoaded
function, 8-8 to 8-9
CVIXDisplay global variable, 9-3
CVIXHiddenWindow global variable, 9-4
CVIXRootWindow variable, 9-3
CxAdd function, 3-7 to 3-8
CxAdd1D function, 3-8 to 3-9
CxDiv function, 3-9
CxDiv1D function, 3-10
CxLinEv1D function, 3-11
CxMul function, 3-12
CxMul1D function, 3-12 to 3-13
CxRecip function, 3-13 to 3-14
CxSub function, 3-14
CxSub1D function, 3-15

D
data acquisition functions. See Easy I/O for
DAQ Library.
data formatting functions. See formatting
functions; scanning functions; status
functions.
DateStr function, 8-9
date/time functions
ANSI C Library, 1-6 to 1-7

© National Instruments Corporation

Index

DateStr, 8-9
GetSystemDate, 8-38
GetSystemTime, 8-39
SetSystemDate, 8-76
SetSystemTime, 8-77
TimeStr, 8-83
DCE device, 5-5
DDE Library functions
callback function, 6-2 to 6-4
functions capable of trigger callback
function (table), 6-4
parameter prototypes (table), 6-3
clients and servers, 6-2
connecting to DDE server, 6-2
DDE data links, 6-4
error conditions, 6-23 to 6-24
function reference
AdviseDDEDataReady, 6-6 to 6-8
BroadcastDDEDataReady, 6-8 to 6-9
ClientDDEExecute, 6-10
ClientDDERead, 6-10 to 6-11
ClientDDEWrite, 6-12 to 6-13
ConnectToDDEServer, 6-2, 6-13
to 6-15
DisconnectFromDDEServer, 6-15
GetDDEErrorString, 6-15 to 6-16
RegisterDDEServer, 6-2, 6-16
to 6-18
ServerDDEWrite, 6-19 to 6-20
SetUpDDEHotLink, 6-2, 6-4, 6-20
to 6-21
SetUpDDEWarmLink, 6-2, 6-4, 6-21
to 6-22
TerminateDDELink, 6-22
UnregisterDDEServer, 6-23
function tree (table), 6-1
Microsoft Excel example, 6-5 to 6-6
DDE transaction types (table), 6-4
Delay function, 8-9 to 8-10
DelayedPulseGenConfig function, 10-34
to 10-36
DeleteDir function, 8-10
DeleteFile function, 8-10 to 8-11
DestroyXProperty function, 9-12 to 9-13
DestroyXPropType function, 9-13 to 9-14
Determinant function, 3-16
© National Instruments Corporation

I-5

device control functions, GPIB
Library, 4-2, 4-7
device drivers, GPIB, 4-5 to 4-7
device I/O functions, GPIB-488.2
Library, 4-3
Device Manager functions, GPIB
CloseDev, 4-6 to 4-7, 4-13
CloseInstrDevs, 4-14
ibInstallCallback, 4-12, 4-14 to 4-17
ibNotify, 4-12
ibNotify function, 4-17 to 4-20
OpenDev, 4-6, 4-21
ThreadIbcnt, 4-22
ThreadIbcntl, 4-22 to 4-23
ThreadIberr, 4-23 to 4-25
ThreadIbsta, 4-25 to 4-26
writing instrument modules (note), 4-7
device numbers, Easy I/O for DAQ
Library, 10-4
digital input/output functions
ReadFromDigitalLine, 10-49 to 10-51
ReadFromDigitalPort, 10-51 to 10-52
WriteToDigitalLine, 10-53 to 10-55
WriteToDigitalPort, 10-55 to 10-56
directory utility functions
DeleteDir, 8-10
GetDir, 8-20
GetDrive, 8-20 to 8-21
GetFullPathFromProject, 8-29 to 8-30
GetModuleDir, 8-31 to 8-32
GetProjectDir, 8-34
MakeDir, 8-54 to 8-55
MakePathname, 8-55
SetDir, 8-66
SetDrive, 8-66 to 8-67
SplitPath, 8-77 to 8-78
DisableBreakOnLibraryErrors function,
8-11 to 8-12
DisableInterrupts function, 8-12
DisableTaskSwitching function, 8-12
to 8-15
DisconnectFromDDEServer function, 6-15
DisconnectFromTCPServer function, 7-7
to 7-8
DisConnectFromXDisplay function, 9-14
to 9-15
LabWindows/CVI Standard Libraries

Index

DisconnectTCPClient function, 7-7
Div1D function, 3-16 to 3-17
Div2D function, 3-17 to 3-18
documentation
conventions used in manual, xix
LabWindows/CVI documentation set, xx
organization of manual, xvii-xviii
related documentation, xx
DotProduct function, 3-18
DTE device, 5-5
Dynamic Data Exchange (DDE). See DDE
Library functions.
dynamic link library, GPIB, 4-5 to 4-6

E
Easy I/O for DAQ Library
advantages, 10-1 to 10-2
calls to Data Acquisition Library
(note), 10-1
Channel String
analog input functions, 10-4 to 10-5
analog output functions, 10-7
classes, 10-3
command strings, 10-6
device numbers, 10-4
error conditions (table), 10-57 to 10-66
function reference
AIAcquireTriggeredWaveforms,
10-8 to 10-13
AIAcquireWaveforms, 10-33
to 10-34
AICheckAcquisition, 10-15
AIClearAcquisition, 10-15
AIReadAcquisition, 10-16 to 10-17
AISampleChannel, 10-17 to 10-18
AISampleChannels, 10-18
AIStartAcquisition, 10-19
AOClearWaveforms, 10-20
AOGenerateWaveforms, 10-21
to 10-22
AOUpdateChannel, 10-22 to 10-23
AOUpdateChannels, 10-23 to 10-24
ContinuousPulseGenConfig, 10-24
to 10-26

LabWindows/CVI Standard Libraries

I-6

CounterEventOrTimeConfig, 10-26
to 10-29
CounterMeasureFrequency, 10-29
to 10-32
CounterRead, 10-32 to 10-33
CounterStart, 10-33
CounterStop, 10-34
DelayedPulseGenConfig, 10-34
to 10-36
FrequencyDividerConfig, 10-37
to 10-39
GetAILimitsOfChannel, 10-40 to
10-41
GetChannelIndices, 10-41 to 10-42
GetChannelNameFromIndex, 10-42
to 10-43
GetDAQErrorString, 10-43 to 10-44
GetNumChannels, 10-44
GroupByChannel, 10-44 to 10-45
ICounterControl, 10-45 to 10-47
PlotLastAIWaveformsPopup, 10-47
PulseWidthOrPeriodMeasConfig,
10-48 to 10-49
ReadFromDigitalLine, 10-49
to 10-51
ReadFromDigitalPort, 10-51
to 10-52
SetEasyIOMultitaskingMode, 10-53
WriteToDigitalLine, 10-53 to 10-55
WriteToDigitalPort, 10-55 to 10-56
function tree, 10-2 to 10-3
limitations, 10-2
overview, 10-1
valid counters for counter/timer
functions (table), 10-7
EnableBreakOnLibraryErrors function, 8-15
EnableInterrupts function, 8-15 to 8-16
EnableTaskSwitching function, 8-16
END message, GPIB, 4-9
end-of-string (EOS) character, GPIB, 4-9
end-or-identify (EOI) signal, GPIB, 4-9
errno global variable, set by file I/O
functions, 1-6
error codes
control functions, 1-8
X Property Library, 9-4 to 9-6
© National Instruments Corporation

Index

error conditions
Analysis Library functions, 3-37
DDE Library functions, 6-23 to 6-24
Easy I/O for DAQ Library, 10-57
to 10-66
RS-232 Library functions, 5-36 to 5-37
TCP Library functions, 7-12
Error control, GPIB, 4-6
Error (iberr) global variable, 4-6, 4-11
error reporting
Analysis Library functions, 3-4
RS-232 Library functions, 5-3
error-related functions. See also status
functions.
DisableBreakOnLibraryErrors, 8-11
to 8-12
EnableBreakOnLibraryErrors, 8-15
GetAnalysisErrorString, 3-19
GetBreakOnLibraryErrors, 8-17
GetBreakOnProtectionErrors, 8-18
GetDDEErrorString, 6-15 to 6-16
GetFmtErrNdx, 2-18
GetRS232ErrorString, 5-22
GetTCPErrorString, 7-8
GetXPropErrorString, 9-15
ReturnRS232Err, 5-28
SetBreakOnLibraryErrors, 8-63 to 8-64
SetBreakOnProtectionErrors, 8-64
to 8-65
example programs. See formatting function
programming examples; scanning function
programming examples.
ExecutableHasTerminated function, 8-16
to 8-17
executables, launching. See standalone
executables, launching.
extended character sets, 1-2
external module utility functions
GetExternalModuleAddr, 8-21 to 8-22
LoadExternalModule, 8-49 to 8-52
LoadExternalModuleEx, 8-52 to 8-54
ReleaseExternalModule, 8-59
RunExternalModule, 8-62 to 8-63
UnloadExternalModule, 8-84 to 8-85

© National Instruments Corporation

I-7

F
fax technical support, Appendix-1
fdopen function, ANSI C Library, 1-9
to 1-10
file I/O functions
CloseFile, 2-7
errno global variable, 1-6
GetFileInfo, 2-17
OpenFile, 2-20 to 2-22
ReadFile, 2-22 to 2-23
SetFilePtr, 2-26 to 2-28
WriteFile, 2-29 to 2-30
file utility functions
CopyFile, 8-7 to 8-8
DeleteFile, 8-10 to 8-11
GetFileAttrs, 8-23 to 8-24
GetFileDate, 8-24 to 8-25
GetFileSize, 8-25 to 8-26
GetFileTime, 8-26 to 8-27
GetFirstFile, 8-27 to 8-29
GetNextFile, 8-33
RenameFile, 8-60 to 8-61
SetFileAttrs, 8-67 to 8-68
SetFileDate, 8-68 to 8-69
SetFileTime, 8-70
SplitPath, 8-77 to 8-78
FileToArray function, 2-11 to 2-12
FillBytes function, 2-13
FindPattern function, 2-13 to 2-14
floating-point modifiers (%f)
formatting functions, 2-37 to 2-38
scanning functions, 2-45 to 2-46
FlushInQ function, 5-18
FlushOutQ function, 5-19
Fmt, FmtFile, and FmtOut functions. See
formatting function programming
examples; formatting functions.
format codes
formatting functions, 2-34 to 2-35
scanning functions, 2-42 to 2-43
format string
formatting functions, 2-33 to 2-35
examples, 2-33 to 2-34
form of, 2-34
format codes, 2-34 to 2-35
LabWindows/CVI Standard Libraries

Index

using literals, 2-40
scanning functions, 2-41 to 2-43
examples, 2-41
form of, 2-41
format codes, 2-42 to 2-43
using literals, 2-48 to 2-49
Formatting and I/O Library functions
function panels
classes and subclasses, 2-2 to 2-3
function tree (table), 2-2
function reference
ArrayToFile, 2-4 to 2-6
CloseFile, 2-7
CompareBytes, 2-7 to 2-8
CompareStrings, 2-8 to 2-9
CopyBytes, 2-9 to 2-10
CopyString, 2-10
FileToArray, 2-11 to 2-12
FillBytes, 2-13
FindPattern, 2-13 to 2-14
Fmt, 2-14 to 2-15, 2-32
FmtFile, 2-15 to 2-16, 2-32
FmtOut, 2-16 to 2-17, 2-32
GetFileInfo, 2-17
GetFmtErrNdx, 2-18
GetFmtIOError, 2-18 to 2-19
GetFmtIOErrorString, 2-19
NumFmtdBytes, 2-20
OpenFile, 2-20 to 2-22
ReadFile, 2-22 to 2-23
ReadLine, 2-23 to 2-24
Scan, 2-24, 2-40
ScanFile, 2-25, 2-40
ScanIn, 2-25 to 2-26, 2-40
SetFilePtr, 2-26 to 2-28
StringLength, 2-28
StringLowerCase, 2-28 to 2-29
StringUpperCase, 2-29
WriteFile, 2-29 to 2-30
WriteLine, 2-30 to 2-31
formatting function programming examples
appending to a string, 2-56 to 2-57
concatenating two strings, 2-56
creating array of file names, 2-47
integer and real to string with
literals, 2-53
LabWindows/CVI Standard Libraries

I-8

integer array to binary file, assuming
fixed number of elements, 2-54
integer to string, 2-50 to 2-51
list of examples, 2-49 to 2-50
long integer to string, 2-51
real array to ASCII file in columns with
comma separators, 2-53 to 2-54
real array to binary file
assuming fixed number of
elements, 2-54
assuming variable number of
elements, 2-55
real to string
in floating-point notation, 2-51
to 2-52
in scientific notation, 2-52
two integers to ASCII file with errorchecking, 2-53
variable portion of real array to binary
file, 2-55
writing line containing integer with
literals to standard output, 2-58
writing to standard output without
linefeed/carriage return, 2-58
formatting functions. See also scanning
functions; string manipulation functions.
asterisks (*) instead of constants in
format specifiers, 2-39
Fmt
description, 2-14 to 2-15
examples, 2-32
FmtFile
description, 2-15 to 2-16
examples, 2-32
FmtOut
description, 2-16 to 2-17
examples, 2-32
format string, 2-33 to 2-35
introductory examples, 2-31 to 2-32
literals in format string, 2-40
purpose and use, 2-31
special nature of, 2-3 to 2-4
formatting modifiers, 2-35 to 2-39. See also
scanning modifiers.
floating-point modifiers (%f), 2-37
to 2-38
© National Instruments Corporation

Index

integer modifiers (%i, %d, %x, %o, %c),
2-35 to 2-37
string modifiers (%s), 2-38 to 2-39
FrequencyDividerConfig function, 10-37
to 10-39

G
gender changer, 5-6
GetAILimitsOfChannel function, 10-40
to 10-41
GetAnalysisErrorString function, 3-19
GetBreakOnLibraryErrors function, 8-17
GetBreakOnProtectionErrors function, 8-18
GetChannelIndices function, 10-41 to 10-42
GetChannelNameFromIndex function, 10-42
to 10-43
GetComStat function, 5-19 to 5-20
GetCurrentPlatform function, 8-19
GetCVIVersion function, 8-18 to 8-19
GetDAQErrorString function, 10-43
to 10-44
GetDDEErrorString function, 6-15 to 6-16
GetDir function, 8-20
GetDrive function, 8-20 to 8-21
GetExternalModuleAddr function, 8-21
to 8-22
GetFileAttrs function, 8-23 to 8-24
GetFileDate function, 8-24 to 8-25
GetFileInfo function, 2-17
GetFileSize function, 8-25 to 8-26
GetFileTime function, 8-26 to 8-27
GetFirstFile function, 8-27 to 8-29
GetFmtErrNdx function, 2-18
GetFmtIOError function, 2-18 to 2-19
GetFmtIOErrorString function, 2-19
GetFullPathFromProject function, 8-29
to 8-30
GetInQLen function, 5-20 to 5-21
GetInterruptState function, 8-30
GetKey function, 8-30 to 8-31
GetModuleDir function, 8-31 to 8-32
GetNextFile function, 8-33
GetNumChannels function, 10-44
GetOutQLen function, 5-4, 5-21

© National Instruments Corporation

I-9

GetPersistentVariable function, 8-33
GetProjectDir function, 8-34
GetRS232ErrorString function, 5-22
GetStdioPort function, 8-35
GetStdioWindowOptions function, 8-35
to 8-36
GetStdioWindowPosition function, 8-36
to 8-37
GetStdioWindowSize function, 8-37
GetStdioWindowVisibility function, 8-37
to 8-38
GetSystemDate function, 8-38
GetSystemTime function, 8-39
GetTCPErrorString function, 7-8
GetWindowDisplaySetting function, 8-39
to 8-40
GetXPropErrorString function, 9-15
GetXPropertyName function, 9-15 to 9-16
GetXPropertyType function, 9-16 to 9-17
GetXPropTypeName function, 9-17 to 9-18
GetXPropTypeSize function, 9-18
GetXPropTypeUnit function, 9-19
GetXWindowPropertyItem function, 9-20
to 9-22
GetXWindowPropertyValue function, 9-22
to 9-25
global variables. See also status functions.
CVIXDisplay, 9-3
CVIXHiddenWindow, 9-4
Error (iberr), 4-6, 4-11
GPIB/GPIB-488.2 libraries, 4-10
rs232err, 5-3
Status Word (ibsta), 4-6, 4-10
GPIB and GPIB-488.2 Libraries
automatic serial polling, 4-7 to 4-8
board functions, 4-7
device functions, 4-7
function panels
classes and subclasses, 4-4 to 4-5
function tree (table), 4-2 to 4-4
functions. See Device Manager
functions, GPIB.
global variables, 4-10
GPIB dynamic link library/device
driver, 4-6
guidelines and restrictions, 4-6 to 4-7
LabWindows/CVI Standard Libraries

Index

hardware interrupts and autopolling, 4-8
to 4-9
overview, 4-1
platform and board considerations, 4-10
to 4-11
read and write termination, 4-9
status and error controls, 4-6
timeouts, 4-9
Windows 95 support, 4-10 to 4-11
compatibility driver, 4-11
native 32-bit driver, 4-10
Windows NT and GPIB driver, 4-11
limitations on transfer size, 4-11
multithreading, 4-11
notification of SRQ and other GPIB
events, 4-12
writing instrument modules (note), 4-7
GPIB device drivers, 4-5 to 4-6
GPIB.DLL, 4-5
GroupByChannel function, 10-44 to 10-45

H
handshaking for RS-232 communications,
5-6 to 5-8
hardware handshaking, 5-7 to 5-8
software handshaking, 5-6
hardware handshaking, 5-7 to 5-8
hardware interrupts and autopolling, 4-8
to 4-9
help, starting. See SystemHelp function.
hidden window for providing X window
IDs, 9-3 to 9-4
Histogram function, 3-19 to 3-20

I
I/O functions. See also Easy I/O for DAQ
Library; Formatting and I/O Library
functions; Standard Input/Output window
functions.
GPIB Library, 4-2
low-level GPIB/GPIB-488.2 I/O
functions, 4-4

LabWindows/CVI Standard Libraries

I-10

port I/O utility functions
inp, 8-42
inpw, 8-42 to 8-43
outp, 8-56
outpw, 8-56
RS-232 Library
ComFromFile, 5-3, 5-9 to 5-10
ComRd, 5-11
ComRdByte, 5-12
ComRdTerm, 5-12 to 5-13
ComToFile, 5-3, 5-15 to 5-16
ComWrt, 5-16 to 5-17
ComWrtByte, 5-17 to 5-18
IBCONF utility, 4-6
ibdev function, 4-6
ibfind function, 4-6
ibInstallCallback function, 4-14 to 4-17
callback function, 4-17
driver version requirements, 4-12
purpose and use, 4-14 to 4-17
SRQI, RQS, and auto serial polling, 4-16
synchronous callbacks, 4-12
ibNotify function, 4-17 to 4-20
asynchronous callbacks, 4-12
callback function, 4-19 to 4-20
driver version requirements, 4-12
purpose and use, 4-17 to 4-20
rearming error (warning), 4-19
restrictions in asynchronous callbacks, 4-20
SRQI, RQS, and auto serial polling, 4-19
ICounterControl function, 10-45 to 10-47
InitCVIRTE function, 8-40 to 8-42
inp function, 8-42
input/output facilities, ANSI C, 1-6
inpw function, 8-42 to 8-43
InstallComCallback function, 5-22 to 5-25
InstallXPropertyCallback function, 9-4, 9-25
to 9-27
InStandaloneExecutable function, 8-43
integer modifiers (%i, %d, %x, %o, %c)
formatting functions, 2-35 to 2-37
scanning functions, 2-43 to 2-45
interrupts
DisableInterrupts function, 8-12
EnableInterrupts function, 8-15 to 8-16
GetInterruptState function, 8-30
© National Instruments Corporation

Index

hardware interrupts and autopolling, 4-8
to 4-9
InvMatrix function, 3-20 to 3-21

K
keyboard utility functions
GetKey, 8-30 to 8-31
KeyHit, 8-43 to 8-44

L
LaunchExecutable function, 8-44 to 8-46
LaunchExecutableEx function, 8-47 to 8-48
launching executables. See standalone
executables, launching.
LC_COLLATE locale, 1-5
LC_CTYPE locale, 1-4 to 1-5
LC_MONETARY locale, 1-4
LC_NUMERIC locale, 1-4
LC_TIME locale, 1-5
LinEv1D function, 3-21
LinEv2D function, 3-22
literals in format string
formatting functions, 2-40
scanning functions, 2-48 to 2-49
LoadExternalModule function, 8-49 to 8-52
LoadExternalModuleEx function, 8-52
to 8-54
local functions, GPIB-488.2 Library, 4-4
locale. See C locale.
low-level I/O functions
ANSI C Library, 1-2
GPIB-488.2 Library, 4-4

M
MakeDir function, 8-54 to 8-55
MakePathname function, 8-55
managing property information. See
property information, managing.
manual. See documentation.
mathematical functions, ANSI C, 1-6

© National Instruments Corporation

I-11

matrix algebra functions. See vector and
matrix algebra functions.
MatrixMul function, 3-23
MaxMin1D function, 3-24
MaxMin2D function, 3-24 to 3-25
Mean function, 3-25 to 3-26
memory access. See physical memory access
functions.
miscellaneous Easy I/O for DAQ functions
GetAILimitsOfChannel, 10-40 to 10-41
GetChannelIndices, 10-41 to 10-42
GetChannelNameFromIndex, 10-42
to 10-43
GetDAQErrorString, 10-43 to 10-44
GetNumChannels, 10-44
GroupByChannel, 10-44 to 10-45
SetEasyIOMultitaskingMode, 10-53
miscellaneous utility functions
Beep, 8-5
Breakpoint, 8-6
CloseCVIRTE, 8-6
Cls, 8-7
CVILowLevelSupportDriverLoaded, 8-8
to 8-9
DisableInterrupts, 8-12
EnableInterrupts, 8-15 to 8-16
GetCurrentPlatform, 8-19
GetCVIVersion, 8-18 to 8-19
GetInterruptState, 8-30
GetWindowDisplaySetting, 8-39 to 8-40
InitCVIRTE, 8-40 to 8-42
InStandaloneExecutable, 8-43
RoundRealToNearestInteger, 8-61
to 8-62
SystemHelp, 8-79 to 8-81
TruncateRealNumber, 8-84
Mul1D function, 3-26 to 3-27
Mul2D function, 3-27
multithreading, Windows 95 and
Windows NT, 4-11

LabWindows/CVI Standard Libraries

Index

N

physical memory access functions

Neg1D function, 3-28
null modem cable, 5-5
NumFmtdBytes function, 2-20

ReadFromPhysicalMemory, 8-57
ReadFromPhysicalMemoryEx, 8-58
WriteToPhysicalMemory, 8-85 to 8-86
WriteToPhysicalMemoryEx, 8-86
to 8-87
PlotLastAIWaveformsPopup
function, 10-47
port I/O utility functions
inp, 8-42
inpw, 8-42 to 8-43
outp, 8-56
outpw, 8-56
properties. See also X Property Library
functions.
definition, 9-2
handles and types, 9-3
property events, handling
GetXPropErrorString, 9-15
InstallXPropertyCallback, 9-4, 9-25
to 9-27
UninstallXPropertyCallback, 9-4, 9-33
property information, managing
CreateXProperty, 9-3, 9-9 to 9-10
DestroyXProperty, 9-12 to 9-13
GetXPropertyName, 9-15 to 9-16
GetXPropertyType, 9-16 to 9-17
property types, managing
CreateXPropType, 9-3, 9-10 to 9-12
DestroyXPropType, 9-13 to 9-14
GetXPropTypeName, 9-17 to 9-18
GetXPropTypeSize, 9-18
GetXPropTypeUnit, 9-19
PulseWidthOrPeriodMeasConfig function,
10-48 to 10-49
PutXWindowPropertyItem function, 9-27
to 9-28
PutXWindowPropertyValue function, 9-29
to 9-31

O
one-dimensional array operation functions
Abs1D, 3-4 to 3-5
Add1D, 3-5
Div1D, 3-16 to 3-17
LinEv1D, 3-21
MaxMin1D, 3-24
Mul1D, 3-26 to 3-27
Neg1D, 3-28
Sub1D, 3-30 to 3-31
Subset1D, 3-32
one-dimensional complex operation
functions
CxAdd1D, 3-8 to 3-9
CxDiv1D, 3-10
CxLinEv1D, 3-11
CxMul1D, 3-12 to 3-13
CxSub1D, 3-15
ToPolar1D, 3-33 to 3-34
ToRect1D, 3-35
open functions
GPIB Library, 4-2
RS-232 Library, 5-1
OpenCom function, 5-4, 5-25 to 5-26
OpenComConfig function, 5-4, 5-26 to 5-28
OpenDev function, 4-6, 4-20
OpenFile function, 2-20 to 2-22
outp function, 8-56
outpw function, 8-56

P
parallel poll functions, GPIB-488.2
Library, 4-4
persistent variable functions
GetPersistentVariable, 8-33 to 8-34
SetPersistentVariable, 8-71

LabWindows/CVI Standard Libraries

I-12

© National Instruments Corporation

Index

R
read termination, GPIB, 4-9
ReadFile function, 2-22 to 2-23
ReadFromDigitalLine function, 10-49
to 10-51
ReadFromDigitalPort function, 10-51
to 10-52
ReadFromPhysicalMemory function, 8-57
ReadFromPhysicalMemoryEx
function, 8-58
ReadLine function, 2-23 to 2-24
RegisterDDEServer function, 6-2, 6-16
to 6-18
RegisterTCPServer function, 7-2, 7-8
to 7-10
ReleaseExternalModule function, 8-59
remote functions, GPIB-488.2 Library, 4-4
remote hosts
ConnectToXDisplay function, 9-3, 9-7
to 9-9
DisConnectFromXDisplay, 9-14 to 9-15
RemoveXWindowProperty function, 9-31
to 9-32
RenameFile function, 8-60 to 8-61
ResetDevs function no longer supported
(note), 4-13
RetireExecutableHandle function, 8-61
ReturnRS232Err function, 5-28
RoundRealToNearestInteger function, 8-61
to 8-62
RQS events, and auto serial polling
ibInstallCallback function, 4-17
ibNotify function, 4-19
RS-232 cables, 5-4 to 5-6
DTE to DCE cable configuration
(table), 5-5
gender of connectors, 5-6
PC cable configuration (table), 5-4
PC to DTE cable configuration
(table), 5-5
RS-232 Library functions
error conditions, 5-36 to 5-37
function panels
classes and subclasses, 5-2
function tree (table), 5-1 to 5-2
© National Instruments Corporation

I-13

function reference
CloseCom, 5-8 to 5-9
ComBreak, 5-9
ComFromFile, 5-3, 5-9 to 5-10
ComRd, 5-11
ComRdByte, 5-12
ComRdTerm, 5-12 to 5-13
ComSetEscape, 5-14 to 5-15
ComToFile, 5-3, 5-15 to 5-16
ComWrt, 5-16 to 5-17
ComWrtByte, 5-17 to 5-18
FlushInQ, 5-18
FlushOutQ, 5-19
GetComStat, 5-19 to 5-20
GetInQLen, 5-20 to 5-21
GetOutQLen, 5-4, 5-21
GetRS232ErrorString, 5-22
InstallComCallback, 5-22 to 5-25
OpenCom, 5-4, 5-25 to 5-26
OpenComConfig, 5-4, 5-26 to 5-28
ReturnRS232Err, 5-28
SetComTime, 5-29
SetCTSMode, 5-7, 5-30
SetXMode, 5-31
XModemConfig, 5-4, 5-31 to 5-33
XModemReceive, 5-3, 5-4, 5-33
to 5-34
XModemSend, 5-34 to 5-35
handshaking, 5-6 to 5-8
reporting errors, 5-3
RS-232 cables, 5-4 to 5-6
troubleshooting, 5-3 to 5-4
XModem file transfer functions, 5-3
rs232err global variable, 5-3
RS-485 AT-Serial board, 5-3
RunExternalModule function, 8-62 to 8-63

LabWindows/CVI Standard Libraries

Index

S
scanning function programming examples
ASCII file to two integers with error
checking, 2-68
ASCII file with comma separated
numbers to real array, with number of
elements at beginning of file, 2-68
to 2-69
binary file to integer array, assuming
fixed number of elements, 2-69
binary file to real array
assuming fixed number of
elements, 2-69
assuming variable number of
elements, 2-69 to 2-70
integer array containing 1-byte integers
to real array, 2-66 to 2-67
integer array to real array, 2-66
with byte swapping, 2-66
list of examples, 2-49 to 2-50
reading integer from standard input, 2-70
reading line from standard input, 2-71
reading string from standard input, 2-70
to 2-71
scanning strings that are not NULterminated, 2-65 to 2-66
string containing binary integers to
integer array, 2-67
string containing IEEE-format real
number to real variable, 2-67 to 2-68
string to integer, 2-59 to 2-60
string to integer and real, 2-61
string to integer and string, 2-63
string to long integer, 2-60
string to real, 2-60 to 2-61
after finding semicolon in
string, 2-64
after finding substring in string, 2-64
skipping over non-numeric
characters, 2-63
string to string, 2-62
string with comma-separated ASCII
numbers to real array, 2-65

LabWindows/CVI Standard Libraries

I-14

scanning functions. See also Formatting and
I/O Library functions; formatting
functions; string manipulation functions.
asterisks (*) instead of constants in
format specifiers, 2-48
format string, 2-41 to 2-43
introductory examples, 2-31 to 2-32
literals in format string, 2-48 to 2-49
purpose and use, 2-40
Scan, 2-24, 2-40
ScanFile, 2-25, 2-40
ScanIn, 2-25 to 2-26, 2-40
special nature of, 2-3 to 2-4
scanning modifiers. See also formatting
modifiers.
floating-point modifiers (%f), 2-45
to 2-46
integer modifiers (%i, %d, %x, %o, %c),
2-43 to 2-45
string modifiers (%s), 2-46 to 2-48
serial communications functions. See
RS-232 Library functions.
serial poll functions, GPIB-488.2
Library, 4-4
serial polling, automatic. See automatic
serial polling.
ServerDDEWrite function, 6-19 to 6-20
ServerTCPRead function, 7-10
ServerTCPWrite function, 7-11
Set1D function, 3-28
SetBreakOnLibraryErrors function, 8-63
to 8-64
SetBreakOnProtectionErrors function, 8-64
to 8-65
SetComTime function, 5-29
SetCTSMode function, 5-7, 5-30
SetDir function, 8-66
SetDrive function, 8-66 to 8-67
SetEasyIOMultitaskingMode
function, 10-53
SetFileAttrs function, 8-67 to 8-68
SetFileDate function, 8-68 to 8-69
SetFilePtr function, 2-26 to 2-28
SetFileTime function, 8-70
SetPersistentVariable function, 8-71
SetStdioPort function, 8-71 to 8-72
© National Instruments Corporation

Index

SetStdioWindowOptions function, 8-72
to 8-74
SetStdioWindowPosition function, 8-74
to 8-75
SetStdioWindowSize function, 8-75
SetStdioWindowVisibility function, 8-76
SetSystemDate function, 8-76
SetSystemTime function, 8-77
SetUpDDEHotLink function, 6-2, 6-4, 6-20
to 6-21
SetUpDDEWarmLink function, 6-2, 6-4,
6-21 to 6-22
SetXMode function, 5-6, 5-31
software handshaking, 5-6
Sort function, 3-29
SplitPath function, 8-77 to 8-78
SRQ functions, GPIB-488.2 Library
function tree, 4-4
Windows NT and Windows 95
asynchronous callbacks, 4-12
device version requirements, 4-12
synchronous callbacks, 4-12
SRQI event, and auto serial polling
ibInstallCallback function, 4-17
ibNotify function, 4-19
standalone executables, launching
ExecutableHasTerminated function, 8-16
to 8-17
LaunchExecutableEx function, 8-47
to 8-48
RetireExecutableHandle function, 8-61
TerminateExecutable function, 8-82
Standard Input/Output window functions
GetStdioPort, 8-35
GetStdioWindowOptions, 8-35 to 8-36
GetStdioWindowPosition, 8-36 to 8-37
GetStdioWindowSize, 8-37
GetStdioWindowVisibility, 8-37 to 8-38
SetStdioPort, 8-71 to 8-72
SetStdioWindowOptions, 8-72 to 8-74
SetStdioWindowPosition, 8-74 to 8-75
SetStdioWindowSize, 8-75
SetStdioWindowVisibility, 8-76
standard language additions, ANSI C, 1-2
to 1-5

© National Instruments Corporation

I-15

statistics functions
Histogram, 3-19 to 3-20
Mean, 3-25 to 3-26
Sort, 3-29
StdDev, 3-29 to 3-30
Status control, GPIB, 4-6
status functions. See also error-related
functions.
Formatting and I/O Library functions
GetFmtErrNdx, 2-18
GetFmtIOError, 2-18 to 2-19
GetFmtIOErrorString, 2-19
NumFmtdBytes, 2-20
RS-232 library
GetComStat, 5-19 to 5-20
GetInQLen, 5-20 to 5-21
GetOutQLen, 5-4, 5-21
GetRS232ErrorString, 5-22
ReturnRS232Err, 5-28
thread-specific, GPIB Library
ThreadIbcnt, 4-22
ThreadIbcntl function, 4-22 to 4-23
ThreadIberr, 4-23 to 4-25
ThreadIbsta, 4-25 to 4-26
Status Word (ibsta) global variable, 4-6, 4-10
StdDev function, 3-29 to 3-30
string manipulation functions
CompareBytes, 2-7 to 2-8
CompareStrings, 2-8 to 2-9
CopyBytes, 2-9 to 2-10
CopyString, 2-10
definition, 2-3
FillBytes, 2-13
FindPattern, 2-13 to 2-14
ReadLine, 2-23 to 2-24
StringLength, 2-28
StringLowerCase, 2-28 to 2-29
StringUpperCase, 2-29
WriteLine, 2-30 to 2-31
string modifiers (%s)
formatting functions, 2-38 to 2-39
scanning functions, 2-46 to 2-48
string processing, ANSI C, 1-5
Sub1D function, 3-30 to 3-31
Sub2D function, 3-31
Subset1D function, 3-32
LabWindows/CVI Standard Libraries

Index

synchronous callbacks, 4-12
SyncWait function, 8-79
system control functions, GPIB-488.2
Library, 4-4
SystemHelp function, 8-79 to 8-81

T
task switching functions
DisableTaskSwitching, 8-12 to 8-15
EnableTaskSwitching, 8-16
TCP Library functions
callback function, 7-2 to 7-3
clients and servers, 7-2
error conditions, 7-12
function reference
ClientTCPRead, 7-3 to 7-4
ClientTCPWrite, 7-4 to 7-5
ConnectToTCPServer, 7-5 to 7-7
DisconnectFromTCPServer, 7-7
to 7-8
DisconnectTCPClient, 7-7
GetTCPErrorString, 7-8
RegisterTCPServer, 7-2, 7-8 to 7-10
ServerTCPRead, 7-10
ServerTCPWrite, 7-11
UnregisterTCPServer, 7-11 to 7-12
function tree (table), 7-1
technical support, Appendix-1
TerminateDDELink function, 6-22
TerminateExecutable function, 8-82
thread-specific status functions
ThreadIbcnt, 4-22
ThreadIbcntl function, 4-22 to 4-23
ThreadIberr, 4-23 to 4-25
ThreadIbsta, 4-25
time/date functions
ANSI C Library, 1-6 to 1-7
DateStr, 8-9
GetSystemDate, 8-38
GetSystemTime, 8-39
SetSystemDate, 8-76
SetSystemTime, 8-77
TimeStr, 8-83
timeouts, GPIB, 4-9

LabWindows/CVI Standard Libraries

I-16

timer/wait utility functions
Delay, 8-9 to 8-10
SyncWait, 8-79
Timer, 8-83
TimeStr function, 8-83
ToPolar function, 3-32 to 3-33
ToPolar1D function, 3-33 to 3-34
ToRect function, 3-34 to 3-35
Transmission Control Protocol Library
functions. See TCP Library functions.
Transpose function, 3-36
trigger functions, GPIB-488.2 Library, 4-3
troubleshooting RS-232 Library functions,
5-3 to 5-4
TruncateRealNumber function, 8-84
two-dimensional array operation functions
Add2D, 3-5 to 3-6
Div2D, 3-17 to 3-18
LinEv2D, 3-22
MaxMin2D, 3-24 to 3-25
Mul2D, 3-27
Sub2D, 3-31

U
UninstallXPropertyCallback
function, 9-4, 9-33
UnloadExternalModule function, 8-84
to 8-85
UnregisterDDEServer function, 6-23
UnregisterTCPServer function, 7-11 to 7-12
Utility Library functions
function panels
classes and subclasses, 8-4 to 8-5
function tree (table), 8-1 to 8-4
function reference
Beep, 8-5
Breakpoint, 8-6
CloseCVIRTE, 8-6
Cls, 8-7
CopyFile, 8-7 to 8-8
CVILowLevelSupportDriverLoaded,
8-8 to 8-9
DateStr, 8-9
Delay, 8-9 to 8-10

© National Instruments Corporation

Index

DeleteDir, 8-10
DeleteFile, 8-10 to 8-11
DisableBreakOnLibraryErrors, 8-11
to 8-12
DisableInterrupts, 8-12
DisableTaskSwitching, 8-12 to 8-15
EnableBreakOnLibraryErrors, 8-15
EnableInterrupts, 8-15 to 8-16
EnableTaskSwitching, 8-16
ExecutableHasTerminated, 8-16
to 8-17
GetBreakOnLibraryErrors, 8-17
GetBreakOnProtectionErrors, 8-18
GetCurrentPlatform, 8-19
GetCVIVersion, 8-18 to 8-19
GetDir, 8-20
GetDrive, 8-20 to 8-21
GetExternalModuleAddr, 8-21
to 8-22
GetFileAttrs, 8-23 to 8-24
GetFileDate, 8-24 to 8-25
GetFileSize, 8-25 to 8-26
GetFileTime, 8-26 to 8-27
GetFirstFile, 8-27 to 8-29
GetFullPathFromProject, 8-29
to 8-30
GetInterruptState, 8-30
GetKey, 8-30 to 8-31
GetModuleDir, 8-31 to 8-32
GetNextFile, 8-33
GetPersistentVariable, 8-33 to 8-34
GetProjectDir, 8-34
GetStdioPort, 8-35
GetStdioWindowOptions, 8-35
to 8-36
GetStdioWindowPosition, 8-36
to 8-37
GetStdioWindowSize, 8-37
GetStdioWindowVisibility,
8-37 to 8-38
GetSystemDate, 8-38
GetSystemTime, 8-39
GetWindowDisplaySetting, 8-39
to 8-40
InitCVIRTE, 8-40 to 8-42
inp, 8-42
© National Instruments Corporation

I-17

inpw, 8-42 to 8-43
InStandaloneExecutable, 8-43
KeyHit, 8-43 to 8-44
LaunchExecutable, 8-44 to 8-46
LaunchExecutableEx, 8-47 to 8-48
LoadExternalModule, 8-49 to 8-52
LoadExternalModuleEx, 8-52
to 8-54
MakeDir, 8-54 to 8-55
MakePathname, 8-55
outp, 8-56
outpw, 8-56
ReadFromPhysicalMemory
function, 8-57
ReadFromPhysicalMemoryEx, 8-58
ReleaseExternalModule, 8-59
RenameFile, 8-60 to 8-61
RetireExecutableHandle, 8-61
RoundRealToNearestInteger, 8-61
to 8-62
RunExternalModule, 8-62 to 8-63
SetBreakOnLibraryErrors, 8-63
to 8-64
SetBreakOnProtectionErrors, 8-64
to 8-65
SetDir, 8-66
SetDrive, 8-66 to 8-67
SetFileAttrs, 8-67 to 8-68
SetFileDate, 8-68 to 8-69
SetFileTime, 8-70
SetPersistentVariable, 8-71
SetStdioPort, 8-71 to 8-72
SetStdioWindowOptions, 8-72
to 8-74
SetStdioWindowPosition, 8-74
to 8-75
SetStdioWindowSize, 8-75
SetStdioWindowVisibility, 8-76
SetSystemDate, 8-76
SetSystemTime, 8-77
SplitPath, 8-77 to 8-78
SyncWait, 8-79
SystemHelp, 8-79 to 8-81
TerminateExecutable, 8-82
Timer, 8-83
TimeStr, 8-83
LabWindows/CVI Standard Libraries

Index

TruncateRealNumber, 8-84
UnloadExternalModule, 8-84 to 8-85
WriteToPhysicalMemory, 8-85
to 8-86
WriteToPhysicalMemoryEx, 8-86
to 8-87

V
va_arg() macro, 1-2
variable argument functions,
LabWindows/CVI support of, 1-2
vector and matrix algebra functions
Determinant, 3-16
DotProduct, 3-18
InvMatrix, 3-20 to 3-21
MatrixMul, 3-23
Transpose, 3-36
void HandlePropertyNotifyEvent
function, 9-7
void_InitXPropertyLib function, 9-7

X

W
wait utility functions. See timer/wait utility
functions.
window functions, standard input/output.
See Standard Input/Output window
functions.
window properties, accessing
GetXWindowPropertyItem, 9-20 to 9-22
GetXWindowPropertyValue, 9-22
to 9-25
PutXWindowPropertyItem, 9-27 to 9-28
PutXWindowPropertyValue, 9-29
to 9-31
RemoveXWindowProperty, 9-31 to 9-32
Windows 95 GPIB support, 4-10 to 4-11
compatibility driver, 4-11
native 32-bit driver, 4-10
Windows NT and GPIB driver, 4-11
limitations on transfer size, 4-11
multithreading, 4-11

LabWindows/CVI Standard Libraries

notification of SRQ and other GPIB
events, 4-12
asynchronous callbacks, 4-12
driver version requirements, 4-12
synchronous callbacks, 4-12
write termination, GPIB, 4-9
WriteFile function, 2-29 to 2-30
WriteLine function, 2-30 to 2-31
WriteToDigitalLine function, 10-53
to 10-55
WriteToDigitalPort function, 10-55 to 10-56
WriteToPhysicalMemory function, 8-85
to 8-86
WriteToPhysicalMemoryEx function, 8-86
to 8-87

I-18

X Property Library functions
callback functions, 9-4
communicating with local
applications, 9-3
ConnectToXDisplay function, 9-3
error codes, 9-4 to 9-6
function panels, 9-1
function reference
ConnectToXDisplay, 9-7 to 9-9
CreateXProperty, 9-3, 9-9 to 9-10
CreateXPropType, 9-3, 9-10 to 9-12
DestroyXProperty, 9-12 to 9-13
DestroyXPropType, 9-13 to 9-14
DisConnectFromXDisplay, 9-14
to 9-15
GetXPropErrorString, 9-15
GetXPropertyName, 9-15 to 9-16
GetXPropertyType, 9-16 to 9-17
GetXPropTypeName, 9-17 to 9-18
GetXPropTypeSize, 9-18
GetXPropTypeUnit, 9-19
GetXWindowPropertyItem, 9-20
to 9-22
GetXWindowPropertyValue, 9-22
to 9-25
InstallXPropertyCallback, 9-4, 9-25
to 9-27
PutXWindowPropertyItem, 9-27
to 9-28
© National Instruments Corporation

Index

PutXWindowPropertyValue, 9-29
to 9-31
RemoveXWindowProperty, 9-31
to 9-32
UninstallXPropertyCallback, 9-4, 9-33
void HandlePropertyNotifyEvent, 9-7
void_InitXPropertyLib, 9-7
function tree (table), 9-2
hidden window, 9-3
overview, 9-1
property handles and types, 9-3 to 9-4
predefined property types (table), 9-3
using outside of LabWindows/CVI, 9-7
X interclient communication, 9-2 to 9-3
XModem file transfer functions
purpose and use, 5-3
XModemConfig, 5-4, 5-31 to 5-33
XModemReceive, 5-3, 5-4, 5-33 to 5-34
XModemSend, 5-3, 5-34 to 5-35

© National Instruments Corporation

I-19

LabWindows/CVI Standard Libraries
Source Exif Data: 
File Type                       : PDF
File Type Extension             : pdf
MIME Type                       : application/pdf
PDF Version                     : 1.2
Linearized                      : Yes
Encryption                      : Standard V1.2 (40-bit)
User Access                     : Print, Copy, Annotate, Fill forms, Extract, Assemble, Print high-res
Create Date                     : 1996:07:12 16:20:37
Producer                        : Acrobat Distiller 2.1 for Macintosh
Modify Date                     : 1996:08:13 16:47:27
Title                           : LabWindows/CVI Standard Libraries Reference Manual
Subject                         : July 1996, P/N 320682C-01
Author                          : National Instruments Tech Pubs
Page Count                      : 454
Page Mode                       : UseOutlines
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