AA 4949A TC VT55 Programming Manual

AA-4949A-TC VT55 Programming Manual AA-4949A-TC VT55 Programming Manual

User Manual: AA-4949A-TC VT55 Programming Manual

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VT55

Programming Manual

Order No. AA-4949A-TC

February 1977

This

document

describes methods and available software for programming

the

VT55 terminal in

the

FORTRAN

and

BASIC-PLUS languages.

VT55

Programming Manual

Order No. AA-4949A-TC

SUPERSESSION/UPDATE

INFORMATION:

For

RT-ll/FORTRAN

users, this manual supersedes

Chapter

1

of

the

FORTRAN/RT-ll

Extensions Manual

(DEC-II-LRTEA-C-D).

For

the

other

operating systems

it contains

new

information.

OPERATING

SYSTEM

AND

VERSION: RT -11 V02C

RSX-llMV03

RSX-IID

V6.2

lAS

V1.1

RSTS/E V6A

SOFTWARE VERSION:

FORTRAN

IV

VIC

BASIC-PLUS

VI

FORTRAN-IV

PLUS V02

First Printing

February

1977

The

information in this

document

is

subject to

change

without notice

and

should

not be construed

as

a

commitment

by Digital

Equipment

Corporation. Digital Equipment Corporation assumes

no

responsibility

for any errors that may appear in this

document.

The

software described in this

document

is

furnished

under

a license

and

may be used or copied only in

accordance with

the

terms

of

such

license.

Digital Equipment Corporation assumes no responsibility for

the

use or reliability

of

its software on equip-

ment

that

is

not

supplied by DIGITAL.

Copyright © 1977 by Digital

Equipment

Corporation

The

following are trademarks

of

Digital

Equipment

Corporation.

COMPUTER

LABS DEC

US

FOCAL MASSBUS

COMTEX DECsystem-IO

INDAC

RSTS

DDT

DIBOL LAB-8 RSX

DEC

DIGITAL

OMNIBUS TYPESET-8

DECCOMM EDUSYSTEM OS/8 TYPESET-IO

DECtape FLIP

CHIP

PDP

TYPESET-II

PHA

UNIBUS

9/77-14

PREFACE

CHAPTER

1

1.1

1.2

1.3

1.4

1.5

1.6

CHAPTER

2

2.1

2.2

2.2.1

2.2.2

2.2.3

2.2.4

CHAPTER

3

3.1

3.1.1

3.1.2

3.1.3

3.1.4

3.2

3.3

3.4

APPENDIX A

A.1

A.2

A.2.1

A.2.2

A.2.3

CONTENTS

GENERAL INFORMATION

......................................

.

GETTING

USED TO

GRAPHIC

TERMS

..........................

.

GRAPHIC

FIGURES

............................................

.

CURSOR CONTROL

............................................

.

MATHEMATICAL

TERMS

......................................

.

TERMS FOR

LARG

E SYSTEMS

..................................

.

FURTHER

READING

..........................................

.

FORTRAN

PROGRAMMING

....................................

.

INTRODUCTION

TO PLOT55

...................................

.

PLOT55 PROCEDURES

.........................................

.

Attaching and Detaching a Terminal (RSX

-11

and lAS Only)

.....

.

Graphic Procedures

.........................................

.

Alphanumeric Procedures

...................................

.

Sending Escape Sequences

...................................

.

BASIC-PLUS

PROGRAMMING

..................................

.

FNV5,

THE

GENERAL

GRAPHIC

FUNCTION

...................

.

Opening and Closing a VT55 for Output.

.......................

.

Graphic Display with

FNV5

...

:

..............................

.

Alphanumeric Display with

FNV5

............................

.

Producing Hard Copy with

FNV5

.............................

.

FNV6,

THE

TEXT

OUTPUT

FUNCTION

.........................

.

FNV7,

THE

INITIALIZATION

FUNCTION

.......................

.

FNV8,

THE

STEP HISTOGRAM

FUNCTION

......................

.

FORTRAN (PLOT55) ASSEMBLY AND LINKING PROCEDURES

....

ASSEMBLING

AN

OBJECT

FILE

................................

.

LINKING

AN

OBJECT

FILE

TO YOUR

PROGRAM

...............

.

Procedure for R T

-11

Users

...................................

.

Procedure for

RSX-ll

Users

..................................

.

Procedure for lAS Users

.....................................

.

iii

Page

v

1-1

1-1

1-2

1-2

1-3

1-4

1-4

2-1

2-1

2-2

2-2

2-3

2-13

2-16

3-1

3-3

3-3

3-3

3-11

3-11

3-13

3-13

3-15

A-I

A-I

A-3

A-3

A-3

A-4

APPENDIX B

B.l

B.2

B.3

B.4

B.5

APPENDIX C

INDEX

C.l

C.2

C.3

CA

CONTENTS (Cont.)

SUGGESTED

PWT55

APPLICATIONS

...........................

.

INITIALIZATION

..............................................

.

GRIDS

AND

COORDINATE

AXES

...............................

.

GRAPH

PLOTTING ROUTINES

.................................

.

LABELING

A

GRAPHIC

DISPLA Y

.............................

..

ATTACHING

THE

VT55

AS

AN

OUTPUT DEVICE

................

.

SUGGESTED BASIC-PLUS APPLICATIONS

......................

.

INITIALIZATION

..............................................

.

GRIDS

AND

COORDINATE

AXES

...............................

.

PLOTTING

GRAPHS

..........................................

..

SHADING

A

GRAPH

...........................................

.

iv

B-1

B-1

B-2

B-2

B-4

B-5

C-l

C-2

C-2

C-4

C-4

Index-l

PREFACE

This manual will introduce you, a new VT55 user, to

the

methods

and

resources

that

take fullest advantage

of

the

VT55's capabilities.

The

VT55 can be used as

the

programming console

of

a very small system

such

as might be found in a laboratory or as

one

of

a large

number

of

terminals for an extensive multiuser com-

puter system, as well as

the

range

of

intermediate applications.

The

programming

methods

outlined in this

book are standard for

all

applications

under

the

programming languages

that

are covered.

In order to

understand

this manual fully, you

should

be

familiar with

PDP-II

FORTRAN (for users

of

the

RT-II,

RSX-llM,

RSX-IID,

and

lAS operating systems) or with BASIC-PLUS (for users

of

the

RSTS/E

operating system).

If

you are new to programming or

need

to refresh your

memory,

consult

the

list

of

asso-

ciated

documents

in Section

1.6.

All

users should first read

Chapter

1

and

then

the

chapter

describing

the

programming language to be employed.

Acquiring a high degree

of

skill in programming takes time,

but

the

VT55 software can still be used by

relatively unsophisticated programmers. You will find that, as with any sort

of

practical experience, VT55

programming

is

easiest to learn by simply working examples

and

progressing to

more

sophisticated applica-

tions as your expertise increases. This book

is

therefore

oriented toward examples which illustrate VT55

features in simple

terms

and

which provide good starting points for beginning graphic programmers.

The

chapter

for each programming language will discuss

the

fundamental

FORTRAN

and

BASIC-PLUS

commands

and

concepts

that

a VT55

programmer

needs

to know to get started.

v

1.1

GETIING

USED

TO

GRAPHIC

TERMS

CHAPTER 1

GENERAL INFORMATION

There

are

many

words which have a special

meaning

in graphic programming,

and

you should try to be

familiar with

them

before getting started.

The

VT55 terminal has

more

than

one

terminal

mode.

The

difference

between

one

terminal mode

and

another

has to do with

the

way data are

interpreted

by

the

computer

when

it

is

either

sending

data to

the

VT55

or

receiving data from it.

There

are

three

modes for

the

VT55 terminal:

Alphanumeric

mode

is

the

one

which

is

in effect when you first

turn

on

the

power to a VT55. This mode

implies

that

letters

and

numbers

you type on

the

terminal will be received and

interpreted

by

the

computer

according to a binary code called

the

American Standard Code for Information

Interchange

(ASCII).

AS-

CII characters are

the

symbols used by

the

computer

to perform calculations

and

most

of

the

other

func-

tions

that

we normally associate with

computers

as strictly computational devices. In fact,

the

old-style "tel-

etypewriter" terminal might

never

leave

alphanumeric

mode at

all

in

the

normal course

of

operation, so in

this

sense

alphanumeric

mode

is

the

"normal" mode

of

the

VT55.

The

VT55,

of

course, can also display graphic figures on its screen such as function graphs, markers, and

lines.

These

figures are

put

together from a special set

of

graphic instructions. In order for

the

computer

to

realize

that

a

stream

of

data contains graphic instructions

rather

than

the

usual ASCII characters,

the

VT55

must

enter

a different mode called graphic mode. While in this

mode

the

VT55 will

send

graphic

instructions only,

and

the

data received by

the

VT55 will be displayed

on

the

screen

in graphical form rath-

er

than

as alphabetic

or

numeric

characters. In

other

words,

the

graphic mode changes

the

way data are

interpreted,

not

the

data themselves.

The

VT55 software discussed in this

manual

will switch

the

VT55 from

one

mode to

the

other

automatical-

ly

when

you

run

programs.

It

is

this feature which allows you to

combine

statements

that display graphs

and

statements

that

display

alphanumeric

characters in

the

same

program.

The

VT55 also has a third, temporary

mode

called escape mode. Data

that

are received by a VT55 in escape

mode

are

interpreted

as "immediate" control instructions for

the

VT55.

These

instructions do

such

things

as erasing portions

of

the

screen,

changing

the

position at which a line

of

text

will

appear, and,

if

your ter-

minal has a "hard copy"

unit

built in, making a paper copy

of

the

VT55 screen.

When

the

terminal has

completed

the

function

commanded

by

such

an escape sequence, it

returns

to its previous mode, and so

the

escape mode

is

only a temporary state. VT55 software covered in this book allows you to

send

escape

sequences to

the

VT55 which force it to

enter

escape mode, perform a function

such

as

the

ones

men-

tioned,

and

then

to

return

to

the

former mode, all with a single

subroutine

call.

The

chapters

for each pro-

gramming

language discuss escape

sequences

in

more

detail.

1-1

Genera/In/ormation

1.2

GRAPHIC

FIGURES

The

VT55 allows you to display

the

following types

of

graphic figures on its

screen:

Graphs, which are plotted on

the

screen

as a series

of

points or line

segments;

Shaded Graphs, with

the

screen

"filled in"

underneath

the

graphed function;

Markers,

which are

short

vertical line

segments

that

can be displayed at

interesting

points on a

graph;

and

Horizontal

or

vertical lines, which

span

the

entire

width

or

height

of

the

screen

and can be used,

for example, to display a grid

or

to

layout

coordinate axes on

the

screen.

At any given time, you can simultaneously display on

the

screen

up to two functions (two graphs, two

shaded

graphs,

or

one

of

each),

up to 24 lines

of

80

alphanumeric

characters, 236 horizontal lines, 512 ver-

tical lines,

and

512 graph markers.

As

you might expect,

the

VT55 has to be in graphic mode for

any

of

these

graphic features to operate; only

in

that

mode will

the

graphic data

be

properly interpreted. Additionally, you

must

specifically

enable

each

graphic figure you wish to use;

the

graphic figures are

not

available immediately

upon

entering

graphic

mode. Enabling a figure

such

as

"Shaded

Graph

1"

does not

mean

that

a

shaded

graph immediately appears

on

the

screen

but

only

that

the

VT55

is

now capable

of

displaying a

shaded

graph;

nor

does

the

enabling

of

this figure

mean

that

the

next

function to be plotted will be identified

thereafter

as Shaded

Graph

1.

Put-

ting a

shaded

graph on

the

screen,

to

continue

with

the

example,

is

a

three-step

process in both program-

ming

languages:

Step 1 invokes graphic

mode

and

enables

Shaded

Graph

1 in a single

subroutine

call;

Step 2

is

a

second

subroutine

call to select Shaded

Graph

1 as

the

next

figure to be plotted;

Step 3

is

a third

subroutine

call

that

tells

the

VT55 to plot Shaded

Graph

1.

In

the

same

subroutine

call employed in Step

1,

you can also selectively disable

each

graphic figure. As you

will see in

some

of

the

examples

in later

chapters,

repeated calls to

the

subroutines

referred to

here

can

make

various graphic figures

appear

on

the

screen

(two

superimposed

graphs, for

example)~

and

then

some

of

the

figures

can

be erased

without

affecting

the

others.

Each

of

the

three

steps

must

be

done

for

every

graphic figure you display on

the

VT55

screen,

but

the

steps

do

not

necessarily have to

occur

in

the

above order. For

example,

the

subroutine

referred to in Step 3,

which plots graphs

and

shaded

graphs,

is

actually telling

the

VT55 to store a value or series

of

values in its

graphic memory.

When

you plot a single point a single value

is

stored,

and

a graph

is

plotted by storing a

series

of

related points.

There

are two sections,

or

registers, in

the

graphic

memory,

one

for

Graph

0

and

one

for

Graph

1.

When,

in Step

3,

you plot Shaded

Graph

1,

you

have

loaded a series

of

values into Register

1,

whether

or

not Shaded

Graph

1 is enabled.

If

you

enable

Shaded

Graph

1 later,

these

values will still be in

Register

1,

so

the

shaded

graph will

appear

on

the

screen

immediately. It follows

that

if

you

then

disable

Shaded

Graph

1,

the

shaded

graph will

vanish

from

the

screen,

but

the

plotting values will still

remain

in

Register

1.

Both

programming

languages

covered

by this

manual

have

a facility for clearing

the

graphic

memory,

that

is, resetting all

the

values in

both

registers to zero.

1.3

CURSOR

CONTROL

When

you first

turn

on

a VT55, a small flashing horizontal line appears in

the

upper

left

corner

of

the

screen

when

the

terminal has

warmed

up. This flashing figure

is

called

the

cursor

and

the

upper

left

corner

is

the

cursor's

home position.

When

the

terminal

is

in

alphanumeric

mode,

the

cursor

shows you

the

posi-

tion at which

the

next

alphanumeric

character

will appear.

1-2

General

Information

When

the

terminal is first switched

on,

it is in alphanumeric mode.

Any

system

commands,

text editing,

and

other

normal programming dialog will appear

on

the

VT55

screen

and

remain there.

The

text

of

these

dialogs will stay

on

the

screen

even

after you

execute

a graphic

command;

graphic

commands

switch to

graphic

mode

but

do

not

contain any instructions to automatically erase alphanumeric characters from

the

screen. VT55 graphic

commands

also are designed to automatically

return

the

terminal to alphanumeric

mode

after

they

complete

the

designated graphic process. You

must

decide

whether

you want only your

graphic program's

output

or

the

program's

output

plus system dialogs on

the

screen.

If

you want to draw a

graph, for example, on a blank screen,

move

the

cursor

to

the

home

position

and

then

command

the

VT55

to erase all

the

text from

the

cursor to

the

bottom

of

the

screen. Both

the

FORTRAN

and

the

BASIC-

PLUS VT55 software contain

commands

that

simplify this operation.

1.4 MATHEMATICAL

TERMS

This manual also uses a few terms borrowed from mathematics to describe plotting graphic figures on a

coordinate system.

VT55 software

under

both

languages allows you to display line segments

on

the

screen

of

any length and at

any position or angle (except vertical). These line segments (not to be confused with

the

vertical and hori-

zontallines

described previously), are drawn on

the

screen

from a particular starting point until

they

con-

nect with a stated destination.

The

language

of

geometry calls this sort

of

"directed" line

segment

a vector,

and

this book uses

the

term to distinguish your variable line segments from

the

previously

mentioned

lines, which are always

either

vertical or horizontal in direction

and

have a fixed length (the height

and

width

of

the

VT55 screen, respectively).

VT55 software allows you to construct a figure from a series

of

vectors and "label"

the

figure as

either

Graph

0

or

Graph

1 (with a Select

command

like

the

command

described in connection with plotting a

shaded graph). Once again, you can use this feature to make figures appear and disappear, or by labeling

portions

of

the

figure differently, to selectively erase part

of

a drawing.

In both programming languages,

the

VT55 constructs graphs from one-dimensional arrays. As you will re-

call, arrays in a program are algebraic variables

that

are created by a

statement

such

as

(for

FORTRAN):

INTEGER

DISPLAY(IOO)

If

you began your VT55 program with this

statement,

you could

then

write additional

statements

to "fill"

the

100 positions

of

DISPLAY with an ordered list

of

numbers

,"for

example:

00

11=1,100

DISPLA Y(I)=SIN(I*3.14159150.)

In both languages,

the

VT55 software

is

designed to plot graphs by reading values from

such

arrays, with a

single

subroutine

call.

The

same

subroutine

call can, with a

minor

change, plot a single isolated point with-

out reference to an array; see

the

chapter

appropriate to your programming language.

In both programming languages, you can

change

the

starting coordinates

of

graphs

and

vectors. You can,

for example, declare

the

starting coordinates to be

the

middle

of

the

screen (x=236 and

y=1l8).

Ifso,

the

next

graph to be displayed starts at x=236,

or

the

next

vector starts at

the

point (236,118).

When

you draw a series

of

vectors, each vector will start at

the

destination point

of

the

previous vector (or

at

the

starting coordinates you have defined, in

the

case

of

the

first vector to

be

drawn). Note also

that

vectors do not have to be enabled,

as

other

figures do.

1-3

Genera/Information

NOTE

The

vector-drawing routines in

both

languages can be used to clear a

single register in

the

graphic

memory

without disturbing

the

other

register. This operation

is

done

by setting

the

graph

number

to

the

number

of

the

register you want to clear

and

then

drawing a vector

from the point (0,0) to

the

point (512,0). Doing

so

will load

the

regis-

ter

with zeroes.

1.5

TERMS

FOR

LARGE SYSTEMS

Each

of

the

input/output

paths in a RSTS/E or

RSX-ll

computer

system

is

assigned a

number

called a

logical

unit

number. This

number,

in effect, tells

the

computer

to

either

send

or receive data

through

a

specific communication channel.

If

the

data are being

sent

to

some

output

device, it

is

obviously important

that

they

end

up at

the

right place, e.g., a line printer

rather

than

a paper tape punch.

The

logical unit

number

tells

the

computer

what the proper destination

is

for a certain stream

of

data,

or

in

the

case

of

input, where to look to find data

on

which to operate. For instance,

the

number

5 in

the

FORTRAN

state-

ment

WRITE

(5,1)

is

a logical unit

number

that

is

normally assigned by

the

FORTRAN

compiler to

the

user's terminal. VT55 software allows you to override this "default" assignment and change the logical unit

number

of

your VT55. This feature will be discussed in detail in

the

chapters

that

follow.

In

the

RSTS/E

operating system,

there

can be a large

number

of

terminals attached to the host computer.

Each terminal, VT55s included, has

an

identification code called a terminal number. A particular installa-

tion will assign codes

such

as

KB20:, for "Keyboard

20,"

to identify an individual device.

The

number

20

would be used in

the

Open VT55

command

described in Section

3.1.1

of

this manual.

In

the

RSX-ll

and lAS systems, event flags are used to "synchronize" several programs (called "tasks")

that

are competing for use

of

the

computer.

If

several tasks are ready to run,

event

flags keep track of, for exam-

ple,

input

or

output

operations

that

are currently underway.

When

a high-priority task

is

waiting for a data

transfer operation to be completed,

the

resources

of

the

computer

can be used by lower priority tasks until

an

event

flag informs

the

system

that

the

data transfer

is

finished. This type

of

synchronization can be

valuable to VT55 programmers using large systems.

If

you fall into this category, consult your system's

Executive Reference

Manual

for information about system directives used for controlling

event

flags. One

form

of

the

subroutine

PLOT55, described in Section

2.2.1

of

this manual,

names

a specific event flag

number

that

can be used to synchronize your VT55 program.

1.6

FURTHER

READING

You will find

the

following manuals helpful if you

need

further

information on BASIC-PLUS,

FORTRAN,

operating systems,

or

the

VT55 hardware.

Languages

BASIC-PLUS Language Manual

(DEC-II-0RBPB-A-D)

IAS/RSX-ll

FORTRAN

IV User's

Guide

(DEC-ll-LMFUA-C-D)

PDP-II

FORTRAN

Language

Reference

Man ual

(DEC-ll-LFLRA-C-D)

RT-Il1RSTS/E

FORTRAN

IV User's

Guide

(DEC-II-LRRUA-A-D)

1-4

Genera/In/ormation

Operating Systems

RSX-llM

Operator's Procedures Manual

(OEC-ll-OMOGA-C-O)

RT-ll

System

Reference

Manual

(OEC-ll-ORUGA-C-O,

ONl,

ON2)

RSTS/E Programming Manual

(OEC-ll-ORPMA-A-O)

RSX-ll

M Executive

Reference

Manual

(DEC-ll-OMERA-C-O)

RSX-110

Executive

Reference

Manual

(OEC-ll-OXERA-A-D)

lAS Executive

Reference

Manual, Volume 1

(DEC-ll-OIEI

A-A-O)

lAS User's

Guide

(OEC-II-0IUGA-A-O)

VT55

Hardware

VT55-E,F OECgraphic Scope Users' Manual

(EK-VT55E-TM-OOn

1-5

2.1 INTRODUCTION

TO

PLOT55

CHAPTER

2

FORTRAN

PROGRAMMING

FORTRAN

control

of

the

VT55

is

provided by a single

subroutine

called PLOT55. A call to this routine

from your main program has

one

of

the

following two forms:

CALL

PLOT550CMO,IX,IY,ITBL)

or

CALL

PLOT550CMO,IX,IY)

ICMO, IX, IY, and ITBL,

the

arguments

of

PLOT55,

must

all

be

integers or, in certain cases, integer arrays.

The

arguments

have

the

following meanings in

the

three-argument

form

of

PLOT55:

ICMO

defines

the

procedure

that

will

be

carried

out

by a single call to PL0T55.

IX is, in most cases,

the

x coordinate of, for example, a point to be plotted

on

the

VT55

screen.

The

specific use

of

this

argument

varies

depending

on

the

procedure being per-

formed (i.e.,

depending

on

the

value

of

ICMO). Its use will be explained for each procedure

in

the

next

section.

I Y is, similarly,

the

y coordinate

of

a point. Its use will also be covered for each procedure.

The

purpose

of

ITBL, which

is

a 16-element integer array,

is

to provide a storage space

that

PLOT55 can

use to store status information (e.g., which graphic figures are enabled) from

one

PLOT55 call to

the

next.

For this reason, ITBL

is

called a status table.

If

you do not specify

the

fourth

argument,

PLOT55

will

use

an

internally

defined

array for

the

same

purpose.

The

use

of

this fourth

argument

in R T

-11

FORTRAN

pro-

grams usually makes

no

difference in

the

way

your

PLOT55 program functions (see Appendix B

of

this

manual

for

some

important

exceptions).

When

you

do

specify ITBL, begin your program with

the

state-

ments:

INTEGER

ITBL(16)

OAT

A ITBLlI6*O/

These

statements

a) define a 16-element array called ITBL,

and

b) fill

the

array with zeroes.

Remember

that

the

ITBL

must

be initialized (as with

the

OAT

A

statement

above) at

the

beginning

of

each

new

PLOT55 program.

2-1

FOR

TRAN

Programming

NOTES

1.

Do

not

use

both

three-

and

four-argument

forms

of

PLOT55

in

the

same

program,

since

doing

so

would

effectively

create

two

separate

ITBLs.

2.

If

you

use

the

four-argument

form in

an

overlaid

program,

ITBL

must

be

placed

in

the

root

of

the

overlay

so

that

all PLOT55

calls

can

gain access

to

it.

3.

RSX -11

and

lAS

users

must

use

the

four-ar-

gument

version

of

PLOT55

at

all times.

2.2

PLOT55

PROCEDURES

There

are

14

procedures

that

you can

control

by

changing

the

value

of

ICMD

in

CALL

PLOT55

(ICMD

IX, IY [,ITBL]).

ICMD

can

be

any

integer

in

the

range

0 to 13, with

the

results

described

in this section. '

NOTE

In

many

cases, you

do

not

have

to specify all

three

(or four)

arguments

in a PLOT55 call.

However,

three-argument

calls

must

always

contain

two

com-

mas,

and

four-argument

calls,

three

commas.

PLOT55

programs

will

function

unpredictably

if

any

commas

are left out.

2.2.1

Attaching

and

Detaching

a

Terminal

(RSX-ll

and

lAS

Only)

Format:

CALL

PLOT55(O,ILUN,IEFN,ITBL)

ILUN

is

the

logical

unit

number

and

IEFN

is

the

event

flag

number.

If

ILUN

is

-1,

the

VT55

terminal

is

detached.

If

ILUN

is

a positive

integer

(1-12),

the

logical

unit

specified by

ILUN

is

attached

to

the

task

being

executed

and

will

not

accept

input

from

another

task.

IEFN,

the

event

flag

number

(1-32),

is

important

in

controlling

the

scheduling

of

tasks in a

multitask

system.

A detailed

explanation

of

this

number

is

beyond

the

scope

of

this book,

but

more

information

can

be

found

on

this

number

(and

the

logical

unit

number)

in

the

Execu-

tive

Reference

Manual

for your

system.

The

actual

function

of

ICMD=O

is

to

store

the

logical

unit

number

(ILUN)

and

event

flag

number

(lEFN)

in

the

status

table (ITBL).

Once

this

function

is

performed,

all

output

from PLOT55 calls (graphic

and

al-

phanumeric

instructions)

is

sent

to

the

device

associated with

ILUN.

The

ICMD=O

call does

not

associate

ILUN

with

the

VT55; you

must

do

that

job

separately, using

any

of

several

methods

available to users

of

lAS,

RSX-l1

M,

and

RSX-IID.

The

system

directive

ASNLUN

is

one

such

method.

ASNLUN

can be written

into

your

program

as

ifit

were a

FORTRAN

subroutine:

CALL

ASNLUN

(I,'TT',17)

In this

example,

17

is

the

octal

terminal

number

of

the

VT55,

so

that

logical

unit

I

is

associated with physi-

cal

device

TTI7:.

Note

that

if

this

call were written

into

a

program

that

was

run

from

TTI5:,

for

example,

2-2

FOR

TRAN

Programming

the

VT55 would

only

display

information

created

by PLOT55. Unless you reassigned logical units 5

and

6

as well,

these

numbers

would

continue

to refer to

the

terminal

interface

(TTI5:)

and

the

line

printer,

respectively. You

could

therefore

keep

the

VT55

screen

free

of

unwanted

alphanumeric

displays,

such

as

the

messages

created

by

PAUSE

statements.

In

any

case, it is

best

to use

ASNLUN

or

some

other

method

to

assign

ILUN

to

the

VT55

before

you call

ICMD=O. See

the

documentation

for

your

operating

system

for

alternative

methods

of

making

this assign-

ment.

Appendix

B suggest a

FORTRAN

subroutine

that

performs

the

assignment

and

attachment

in a single

call.

NOTE

ICMD=O

is

useful

only

under

the

RSX

-11

and

lAS

systems.

This

command

form

can

appear

in R T

-11

programs, too,

but

will

not

perform

any

operation.

2.2.2

Graphic

Procedures

Select

Graph

Number

(ICMD=l)

Format:

CALL

PLOT55

{I,IGRF,[,ITBLD

IG R F, always

either

0

or

1,

specifies

the

graph

number

of

the

next

graph

(regular

or

shaded)

to be plotted. This

number

will

be

the

label

of

the

next

regular

or

shaded

graph

to

be

plotted

and

will be

the

label

of

that

figure as long as

the

figure is

enabled.

Note

that

this value

of

ICMD

does not display

or

plot a graphic figure

but

only identifies

the

register

that

will

contain

the

plotting values for

the

graph. Plotting

the

figure actually loads this register with plotting

values (see

ICMD=3),

and

enabling

the

figure

(lCMD=2)

allows it to

appear

on

the

screen

as

soon

as it

is

plotted.

Enable

or

Disable

Graphic

Figures

(ICMD=2)

Format:

CALL

PL0T55

(2,IEN

AB,IDISAB[,ITBLD

This call

is

the

"fundamental"

form

of

PLOT55,

because

graphic figures

cannot

be

displayed

until

they

have

been

enabled.

Therefore,

you will, in

most

cases,

want

this

form

to

be

one

of

the

first calls to PLOT55 in

your

program.

Of

course,

this form

can

also

appear

later in

the

program

if

you

want

to

enable

some

new

figure

or

to disable a figure

that

is already

on

the

screen.

IENAB

and

IDISAB

are

lists

of

figures to be

enabled

or

disabled, respectively. You

can

use

the

following values in

these

two

lists:

=

Enter

(leave) graphic

mode.

2 =

Enable

(disable)

Graph

O.

4 =

Enable

(disable)

Graph

1.

8 =

Enable

(disable)

Shaded

Graph

O.

2-3

FOR

TRAN

Programming

16

= Enable (disable) Shaded Graph

1.

32

= Enable (disable) horizontal lines.

64 = Enable (disable) vertical lines.

128 = Enable (disable) markers for Graph (or Shaded Graph)

O.

256 = Enable (disable) markers for Graph (or Shaded Graph)

1.

512 = Disable

all

graphic figures and clear the graphic memory (IENAB only).

To enable or disable more than one figure in a single PLOT55 call, you can enter lists

of

num-

bers, separated by plus signs, for

lEN

AB

or IDISAB. For example, instead

of

putting the

number

1 in

the

IENAB position (to enter graphic mode), you could put 1 +2+4+512, which

would first clear

the

graphic memory and then enter graphic mode and enable Graph 0 and

Graph

1.

NOTES

1.

If

you enter

the

same

number

for both IENAB

and IOISAB,

the

graphic figure for that

number

will

be enab led.

2.

You can also

enter

the

sum

of

several numbers

rather than a list, e.g.,

the

number

24

(instead

of

8+

16)

to represent both shaded graphs. Howev-

er, your program

will

be more easily understood

by other users

if

you avoid this practice.

3.

As

a matter

of

good practice you should always

include the 512 argument in the IENAB posi-

tion the first time you call PLOT55 with

ICMO=2, e.g.,

CALL PLOT55(2,1 +512+2,)

This three-argument example would put the

terminal in graphic mode, enable Graph

1,

and

also would clear

all

previous graphic informa-

tion from the status table and memory.

If

you

were running several graphic programs in se-

quence, the 512 would erase

the

graphic output

of

the last program from the screen before dis-

playing a new figure. (Notice also that in the

sample call above,

the

IOISAB position

is

emp-

ty, indicating that no graphic figures are being

disabled,

but

that

the

"trailing" comma

is

still in-

cluded.)

4.

It

is

usually not desirable to enable different

fig-

ures with

the

same label (for instance, both

Graph 0 and Shaded Graph 0).

2-4

FOR

TRAN

Programming

Plot Graph (ICMD=3)

After you have enabled a graph and selected its label (ICMD=2

and

ICMD=I,

respectively),

you can use

ICMD=3

to plot

the

figure.

Format: CALL PLOT55 (3,IX,IY[,ITBL])

or

CALL PLOT55(3,IX,IARRAY[,ITBL])

When

the

first format

is

used,

ICMD=3

will display a single point

on

the

screen at

the

coordi-

nates given by IX

(0-510

and IY (0-235).

When

you use

the

second format, IX should be a negative integer and

IARRAY

an integer

array

that

you have previously filled with a series

of

values. In this form,

ICMD=3

will plot a

series of points on the screen.

The

number

of

points plotted

will

be

the

absolute value

of

IX;

the

same

number

of

y coordinates will be selected from

IARRA

Y,

starting with

the

first ele-

ment

of

the

array; and the points will be separated by one unit in

the

x direction.

For example,

CALL PLOT55(3,100,100)

will plot a single point

on

the

screen at a position 100 units from

the

bottom

of

the

screen

(y=

100) and 100 points from

the

left edge (x=IOO).

The

other

form,

CALL PLOT55 (3,-1 OO,ISINE)

would plot a sine function on

the

screen (assuming

that

ISINE has

been

identified in a DI-

MENSION

statement

and filled with sine values before this call to PLOT55).

The

sine

function would be made

of

100 points (the absolute value ofIX=-IOO), and each point would

be separated from neighboring points by one x unit on the screen.

NOTE

It

is

generally necessary to define a starting x posi-

tion (ICMD=7) before plotting regular or shaded

graphs.

It

is

not possible to assign two or more y val-

ues to

the

same x value in a single graph; therefore,

vertical lines cannot be plotted with ICMD=3.

Example I demonstrates

the

use

of

ICMD=I,

ICMD=2, and

ICMD=3

to display a series

of

functions on the VT55 screen.

2-5

Example 1

...

""

...

""

...

""

...

""

...

3

...

w

...

'"

...

""

FOR

TRA N

Programming

INTEGER

ARYSIN(500),ARYCJSC500),ARYEXP(500)

DATA

PI/3.141S91

ENABLE

GRAPHIC

MODE

AND

~RAPHS

0

AND

1

CALL

PLOfSS(2,1+2+4+512,)

fILL

UP

rH~

COSINE, SINE

AND

~XPONENTIAL

ARRAYS

DO

3

1=1,500

EXPARG=I/50.

rHETA=PI*EXPARG

ARYSINCI)=SlNCTHETA)*100.+100.

ARYCOSCl)=COS(THETA)*100.+100.

ARYEXPCI)=EXPCEXPARG)

DEFINE

STARTING

COORDINATES

AT

(0,0),

SELE:T

GRAPH

0,

AND

PLOT

THE

SINE

fUNCTION

CALL

PLOTS5(7,0,0)

CALL

PLOrSS(l,O,)

CALL

PLOTSS(3,-SOO,ARYSIN)

READCS,2)

KR

2

FORMATCI2)

...

..

...

w

...

""

...

..

~

...

...

""

...

..

...

..

...

""

...

..

...

w

...

...

...

...

...

...

PLOT

THE

COSINE

fUNCTION

AS

GRAPH

1

CALL

PLOT55(1,1,)

CALL

PLOT55(3,-500,ARYCDS)

READ(S,2)

KR

ENABLE

THE

SHADED

GRAPHS

AND

DISABLE

THE

GRAPHS

CALL

PLOfSS(2,8+16,2+4)

PLOT

THE

EXPONENTIAL

AS

SHADED

GRAPH

0

AND

THE

COSINE

AS

SHADED

GRAPH

1 •

CALL

PLOfS5(1,O,)

CALL

PLOTSS(3,-SOO,ARYEXP)

CALL

PLOTS5(1,1,)

CALL

PLOTSS(3,-500,ARY:OS)

READ(S,2)

KR

DISABLE

SHADED

GRAPH

1

CTHE

CALL

PLOrS5(2,,16)

READ(S,2)

KR

REENABLE

GRAPH

0

AND

DISABLE

fHE

EXPONENTIAL

TO

A

REGULAR

CALL

PLOTS5(2,2,8)

READ(5,2)

KR

END

2-6

COSINE

FUNCTION)

SHADED

GRAPH

0,

CHANGING

GRAPH.

FOR

TRAN Programming

Notes on Example

1:

1.

The subroutine PLOT55(7,0,0) defines a starting x position (x=O) for

all

the

graphs to be dis-

played by the program. Unless you want to change

the

starting position

of

graphic figures,

you do not have to repeat this call.

2.

The statements READ(5,2)

KR

are used in this example to make

the

program pause be-

tween each graphic display. Each time this statement

is

reached,

the

computer

will

attempt to

read a character from

the

keyboard (logical unit 5); when you type a carriage return on

the

keyboard the program

will

continue.

FOR

TRAN

provides a better method, the PAUSE statement, for doing

the

same thing, but

using it

will

make

the

letters "PAUSE--" appear on the screen each time

the

program reaches

a PAUSE statement. A later example

will

show you how to remove this sort

of

undesired text

from

the

screen.

(IAS/RSX-ll

users: see Section

2.2.3

for a further discussion

of

the PAUSE

statement.)

3.

At this point, you should try running this example program.

It

will

function

as

follows:

a)

First, Graph

0,

a sine function,

will

be traced out on

the

screen

of

the VT55 by 100 dots.

b) Type a carriage return, and Graph

1,

a cosine function,

will

also appear. Notice that the

sine and cosine functions have the same starting x position.

c) Type another carriage return, and both graphs

will

disappear and be replaced by Shaded

Graphs 0 and

1,

which represent

the

exponential and cosine functions, respectively.

d) Type another carriage return and Shaded Graph 1

will

be disabled, making

the

cosine

function vanish.

e) Typing a final carriage return

will

disable

the

shaded graphs and reenable Graph

O.

This

time

the

Graph 0 label

is

given to the exponential function, so the shaded graph

of

the

exponential

will

be replaced with a regular graph

of

the

same function.

Plot Horizontal Line (ICMD=4)

Format: CALL PL0T55(4,IDISP,IY[,ITBLj)

This form

is

used to either erase or display horizontal lines that span the entire width

of

the

screen.

IDISP

is

set to 0 to erase a line or to 1 to display a line.

IY

gives the y coordinate (0 to 235)

of

the line to be erased or displayed.

2-7

FORTRAN

Programming

Plot Vertical Line (ICMD=5)

Example 2

...

..

..

...

..

...

..

...

...

...

..

...

...

...

...

...

...

...

..

...

Format: CALL PLOT55 (5,IX,IDISP[,ITBL))

This form

is

very similar to

the

previous ICMD=4,

but

controls vertical rather than horizon-

tal lines. Note that

the

position

of

IDISP

is

different for this format than for ICMD=4.

IX

gi

ves

the

x coordinate (0 to

5(1)

of

a vertical line to be erased or displayed.

IDISP

is

set

to 0 to erase a line or to 1 to display a line.

Example 2 demonstrates

the

use

of

both line types.

THIS

SAMPLE

PROGRAM

SHONS

HOW

TO

DRAN

AND

ERASE

HORIZONTAL

AND

VERTI:AL

LINES

B~GIN

BY

RESETTING

THE

GRAPHIC

MEMORY

(THE

512

ARGU~ENT)

AND

ENABLING

BJrH

LINE

TYPES

CALL

PLOr55(2,1+32+64+512,)

NEXT

DRAN

51

VEHTICAL

LINES

D(J

1

1=2,502,10

1

CALL

PLOr55(5,I,1)

READ(5,2)

KR

2

fORMAT(A2)

...

...

...

...

NON

DRAw

IN

24

HORIZONTAL

LINES

ro

fJRM

A

GRID

J

DO

3

1=2,232,10

CALL

PLOr55(4,1,I)

READ(5,2)

KR

...

...

..

...

..

...

ERASE

THE

VERTICAL

LINES

DO

4

1=2,502,10

4

CALL

PL(Jr55(5,I,O)

END

Notes on Example

2:

As

the

example shows,

ICMD=4

and

ICMD=5

can each be used to either erase or display horizontal and

vertical lines. Again,

the

READ

statement

is

used to insert temporary pauses, preventing unwanted text

from appearing on

the

screen.

2-8

FOR

TRAN

Programming

Plot

Markers

(ICMD=6)

Format: CALL PLOT55(6,IX,IDISP[,ITBL))

With this command, you can place markers (short vertical line segments) at any points on a

regular or shaded graph.

The

markers for

Graph

0 and for

Graph

1 must

be

enabled separate-

ly (see ICMD=2).

When

you call PLOT55 with ICMD=6, markers will be displayed

on

the

graph

that

has cur-

rently been selected (see ICMD=1).

The

following example illustrates a

common

error:

CALL PLOT55(2,1+2+4+256,) (Enable both graphs and markers for

Graph

1)

CALL PLOT55(1,0,) (Select

Graph

0)

CALL PLOT55(6,50,1) (Plot marker at x=50)

This example will not work, because the second call selected

Graph

0,

and only

the

markers for

Graph

1 have been enabled.

If

you plan to use markers in a graphic display,

avoid this problem by enabling both sets

of

markers

when

you use both

Graph

0 and

Graph

1 (or Shaded

Graph

0 and Shaded

Graph

1). You

will

still have to be careful,

of

course, to

ensure

that

a marker

is

placed on

the

correct graph.

IX, an integer from 0 to 511, gives

the

x coordinate at which the

marker

will appear.

If

a

graph exists at

that

x position,

the

marker will appear on the graph; if

there

is

no graph at

that

x position on

the

screen, the marker

will

appear on

the

y=O

line at the bottom

of

the

screen.

IDISP

will

cause

the

marker to either be erased (IDISP=O) or displayed (IDISP= 1).

Example 3 demonstrates the proper use

of

markers.

2-9

Example 3

...

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...

'"

...

...

..

...

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1

...

...

...

...

...

..

FOR

TRAN

Programming

THIS

PROGRAM

DEMONSTRATES

THE

USE

OF

MARKERS

ON

GRAPHS

AND

SHADED

GRAPHS

INTEGER

ARISIN(SOO)

DATA

PI/3.141S91

RESET

THE

GRAPHIC

MEMORr,

ENTER

GRAP~IC

MODE,

AND

ENABLE

GRAPH

0

AND

MARKERS

FOR

GRAPH

0

CALL

PLOTSS(2,512+1+2+128,)

FILL

THE

ARRAY

WITH

A

SINE

fUNCTION

DO

1

1=1,500

ARrSIN(I)=SIN(Pl*I/SO.)*100.+100.

DEFINE

STARTING

X

COORDINATE,

SELECT

GRAPH

0,

AND

PLOT

THE

SINE

FUNCTI3N

•

CALL

PLOT55(7,0,O)

CALL

PLOT5S(1,0,)

CALL

PLOTS5(3,-500,ARrSIN)

READ(5,2)

KR

2

FORMAT(I2)

'"

...

...

...

...

...

PUT

A

MARKER

ON

GRAPH

0

EV~Rr

25

X

UNITS

DO

3

1=25,500,25

3

CALL

PLOT55(6,I,1)

READ(5,2)

KR

...

...

..

...

..

..

...

...

...

..

...

..

..

...

NOW

DISABLE

GRAPH

0

AND

ENABLE

SHADED

GRAPH

0:

PLOTTING

THE

SINE

AS

A

SHADED

GRAPH

CALL

PLOT55(2,8,2)

READ(5,2)

KR

REMOVE

THE

MARKERS,

BUT

LEAVE

THE

SHADED

GRAPH

DO

4

1=25,500,25

4

CALL

PLOT55(6,I,O)

READ

(5,2)

KR

END

2-10

FOR

TRA

N

Programming

Define

Starting

Coordinates

(ICMD=7)

Format:

CALL

PLOTSS(7,IX,IY[,ITBL])

This call defines

the

starting

x position for regular or

shaded

graphs

(lCMD=3)

and

the

start-

ing x and y positions for vectors

(ICMD=8).

PLOTSS will read

the

x

and

y coordinates

that

you supply as IX

and

IY

and

will

store

them

in its status table.

IX should be

an

integer

between

0

and

Sil.

IY, also an integer,

must

be

between

0

and

23S.

Note

that

when

you draw vectors

(ICMD=8),

the

starting coordinates

change

each

time

you

draw a vector. If, for instance, you

want

several vectors to

start

from

the

same

point, you

have

to redefine

the

starting coordinates (with

ICMD=

7) before drawing

each

vector.

When

you draw graphs,

the

starting y coordinate will be supplied in

your

ICMD=3

call, as

the

first

element

ofIARRA

Y.

Draw Vector

(lCMD=8)

NOTE

The

starting

coordinates you

define

do

not

affect

the

placement

of

single points by

the

ICMD=3

call.

For example,

CALL

PLOTSS(3,IOO,lOO)

will always plot a point 100 units from

the

left

of

the

screen

and

100 units from

the

bottom, regardless

of

the

starting

coordinates you

have

defined.

Format:

CALL

PL0T5S(8,IX,IY[,ITBL])

After

you have

defined

starting

coordinates with

ICMD=7,

you

can

use this call to draw line

segments

on

the

screen.

The

first vector you draw will start at

the

previously

defined

starting

coordinates

and

end

at

the

point (IX,IY).

IX,

an

integer from 0 to

Sll,

is

the

x coordinate

of

the

destination

of

the

vector.

IY, which

can

be

from 0 to 23S,

is

the

y coordinate

of

the

destination.

For

example,

the

series

CALL

PL0T5S(7,100,100)

CALL

PLOTSS(8,ISO,ISO)

will

draw

a vector from

(l00,100)

to (lSO,ISO).

2-11

Example 4

..

..

..

...

..

...

..

...

..

..

...

..

..

..

..

..

..

...

..

..

..

..

..

..

..

..

..

..

..

...

..

..

..

..

..

..

FOR

TRAN

Programming

NOTE

After drawing a vector to (IX,IY), ICMD=8 resets

the starting coordinates to (IX,IY).

If

you draw a se-

ries

of

vectors, each one (except the first)

will

start

where the previous vector ended.

It

is

not possible

to draw an absolutely vertical vector, because no

two y values can apply to the same x coordinate for

the same graph number.

Example 4 demonstrates the use

of

Define Starting Coordinates and Draw Vector calls. No-

tice that ICMD=7

is

only used once, so that the vectors

will

be connected to each other.

THIS

PRO~RAM

SHOwS

HJw

TO

DEFINE

STARTING

COORDINATES

AND

HOw

TO

PLOT

VECTORS.

IT

WILL

DRAW

A

DIA~JND

IN

THE

MIDDLE

OF

THE

VT55

S:REEN

•

FIRST

CLEAR

THE

SCREEN

OF

GRAPHI:

FIGURES

•

CALL

PLOTs5(2,512,)

THEN

ENTER

GRAPHIC

MJDE

AND

ENABLE

GRAPHS

0

AND

1 •

CALL

PLOr55(2,1+2+4,)

SELECT

GRAPH

0

FOR

THE

TJP

OF

THE

DIAMOND

AND

DEFINE

STARTING

COURDINATES

OF

(100,100)

CALL

PLOT55(1,O,)

CALL

PLOIS5(1,100,100)

NOW

DRAW

THE

TOP

TwO

LINES

USING

ICMD=8

(DRAw

VECTOR)

•

NOTICE

THAT

THE

SECOND

LINE

~ILL

BE

DRAWN

STARTING

~HERE

THE

FIRST

LINE

ENDED

•

CALL

PLOT5s(8,lS0,150)

CALL

PLOT5S(8,200,100)

NOw

SELECT

GRAPH

1

FOR

THE

BOTTOM

TWJ

LINES

AND

DRAW

THEM

•

CALL

PLOTS5(1,1,)

CALL

PLOTS5(8,150,SO)

CALL

PLOTSS(ij,100,100)

READ

(5,1)

KR

1 rORMAT(I2)

..

..

..

..

..

..

..

..

..

..

ro

DEMONSTRATE

THE

FACT

fHAT

THERE

ARE

TWO

SEPARATE

FIGURES

IN

THE

SCREEN,

ERASE

THE

BOTTOM

OF

THE

DIAMOND

a1

DISABLING

GRAPH

1 •

CALL

PLOTSS(2,,4)

END

.2-12

FORTRAN

Programming

2.2.3 Alphanumeric Procedures

Position Cursor (ICMD=9)

Format: CALL PLOT55(9,IX,IY[,ITBL])

This simple command positions the cursor at the point (IX,IY).

IX can be from ° to 79; and

IY

can be from ° to

23

You can use this command to decide where the next display

of

alphanumeric characters

will

appear on

the

screen. IX will give

the

column

number

(with ° being the leftmost column)

and

IY

will

be the line

number

(line °

is

the

top line on

the

screen).

Erase from Cursor to End of Screen (ICMD=10)

Format: CALL PLOT55

(1

0" [,ITBL])

NOTE

The

"x"

and

"y"

positions are always empty, but you

must still include

the

two commas (three if ITBL

is

specified).

This

command

erases

all

alphanumeric characters from the present cursor position to

the

end

of

the

screen.

The

position

of

the

cursor is not changed by

ICMD=

1

0.

Graphic figures are not affected

by

ICMD=10.

The subroutine CLEAR, shown in Example

5,

uses

ICMD=9

and ICMD=lO to clear

the

en-

tire screen.

CLEAR functions by first returning

the

cursor to the

home

position:

CALL PLOT55(9,0,0)

and

then

erasing from this position to

the

end

of

the

screen:

CALL PLOT55 (10,,)

Erase from Cursor to End of Line

(ICMD=l1)

Format: CALL PLOT55(11,,[,ITBL])

This call performs the same sort

of

procedure

as

ICMD=lO;

but

it only erases text from

the

present cursor position to

the

end

of

the

line. As with ICMD=10,

the

erasure does

not

change the cursor's position, nor does it change

the

status

of

graphic figures.

2-13

FORTRAN

Programming

Display Text (ICMD=12)

Example 5

...

...

...

...

..

...

..

....

...

...

..

...

...

...

...

...

..

..

'"

..

...

Formats: CALL PLOT55 (12,,'

ANY

TEXT

STRING'[,ITBL])

or

CALL PLOT55(12,ICHARS,IALPHA[,ITBL])

Both formats will display strings

of

alphanumeric characters, with

the

first character appear-

ing at the cursor position.

The

first format

will

display any text string that

is

inserted between the single quotation

marks; in the example shown here,

the

letters

ANY

TEXT STRING would appear at

the

cursor position.

The

second format can function in two modes, both

of

which display charac-

ters from

the

"alphanumeric array," IALPHA. These modes are selected by the argument

ICHARS.

If ICHARS

is

omitted or

is

0,

PLOT55

will

display characters that are listed in

the

third argu-

ment

until it finds a

NUL

character (000).

The

example with a text string in single quotes

shows this mode in operation, because

FORTRAN

automatically puts a

NUL

at

the

end

of

text strings in single quotes.

If

ICHARS

is

some positive integer, it will determine the

number

of

characters from IAL-

PHA that will be displayed.

Example 5 shows how to display alphanumeric text with

the

use

of

ICMD=10,

ICMD=II,

and

ICMD=

12.

Notice that a NUL character (000)

is

loaded into

the

last word

of

IALPHA to

provide an

end

mark.

IHIS

PROGRAM

DEMONSTRATES

ALL

OF

THE

"ALPHANU~ERl:"

fORMS

OF

PLOT55

•

ICMD

: 9

AND

ICMD

=

10

ARE

USED

IN

A

SUBROUTINE

CALLED

"CLEAR,"

~HlCH

ERASES

EXIRA

fEXT

FRO~

THE

SCREEN

•

AS

A

PRELIMINARY

STEP

TO

ICMD

=

12,

~JU

~UST

DEfINE

AN

"ALPHANU~ERIC

ARRA~"

THAT

CAN

BE

USED

TO

STORE

TEXT:

LOGICAL*1

lALPHA(SI)

DATA

IALPHA/80*'

',01

THE

LAST

~ORO

IN

lALPHA

~UST

BE

000,

~HI:H

~ILL

BE

INTERPRETED

AS

A

"NULL"

:HARACTER

AND

~ILL

TELL

lCMO

=

12

ro

STOP

DISPLAYING

CHARACTERS

FRJM

IALPHA

•

CLEAR

THE

STATUS

TABLE

AND

THE

S:REE~:

CALL

CLEAR

CALL

PLOfSS(2,512,)

2-14

...

'"

..

...

..

...

..

...

FOR

TRAN

Programming

PUT

THE

:URSOR

AT

THE

BEGINNING

OF

LINE

12

ANC

DISPLAY

A

MESSAGE:

CALL

PLOTSS(9,O,12)

CALL

PLOTS5(12,,'WHEN

YOU

TYPE

A

CARRIAGE

REtURN,

THE

X

SYMBOLS

WILL

VANISH:

[1234S67890]<>.+@#\")

READ

( 5 ,

1)

KR

1 fORMAT(I2)

...

...

...

...

...

...

..

...

...

...

...

...

..

...

..

...

..

...

...

...

...

...

THESE

TW~

PLOT

55

CALLS

WILL

ERASE

ALL

THE

CHARACTERS

AfTER

"VANISH:" •

CALL

PLOT55(9,60,12)

CALL

PLOr55(11,,)

PAUSE

TYPE

ANOTHER

CARRIAGE

RETURN

TO

ERASE

THE

~CREEN

AGAIN

•

CALL

CLEAR

NOW

WE'LL

USE

THE

ALPHANUMERIC

ARRAY,

fILLING IT

WITH

CHARACTERS

YOU

TYPE

IN

fROM

THE

KEYBOARD

•

CALL

PLOT55(9,O,12)

CALL

PLOrS5(12i,'TYPE.

UP

TO

ONE

LINE

Of

CHARACTERS

AND

X A

CARRIAGE

RETURN')

CALL

PLOTSS(9,O,14)

READ(S,2)

(IALPHA(J),J=1,aO)

2

fORMAT(BOA1)

...

...

..

...

...

...

...

...

...

...

...

...

...

...

...

..

...

...

STATEMENT

3

WILL

DISPLAY

ALL

THE

CHARACTERS

YJU

ENTERED,

BECAUSE

PLOT55

WILL

KEEP

GOING

UNTIL

Il

HITS

rHE

"NULL"

CHARACTER

IN

IALPHA(81) •

YOU

wILL

DECIDE

~OW

~ANY

CHARACTERS

WILL

BE

DISPLAYED

BY

STATE~ENT

S

BY

TYPING

AN

INTEGER

(1-80)

IN

RESPONSE

ro

THE

PROGRAM'S

REQUEST

•

CALL

PLOT5S(9,O,12)

3

CALL

PLOrSS(12"lALPHA)

CALL

PLOr55(9,O,14)

CALL

PLOrS5(12,,'TYPE

A

~UMBER

Of

CHARACTERS

AND

A

<CR>:')

READ(S,4)

lCHARS

4

fORMAT(12)

CALL

PLOrS5(9,O,14)

CALL

PLOfSS(11,,)

5

CALL

PLOfSS(12,ICHARS,IALPHA)

PAUSE

CALL

CLEAR

ENO

2-15

FOR

TRAN Programming

SUBROUTINE

CLEAR

CALL

PLOT55(9,O,O)

CALL

PLOT55(10,,)

RETURN

END

NOTE

In

lAS

operation,

the

PAUSE

statement

is

ignored.

The

READ

statement

should

be

used instead.

In

RSX-ll

systems

the

PAUSE

statement

will

sus-

pend

the

task,

which

must

be

restarted with

the

MCR

command

RESUME:

> RES

taskname

<

CR

>

Merely typing a carriage

return

will

not

resume

the

task in

RSX-ll.

When

you

run

an

RSX-ll

task con-

taining PAUSE

statements,

give it a specific task

name,

for instance:

RUN

EXAMI/TASK=EXAM

<CR>

where

EXAMl.TSK

is

the

name

of

the

file contain-

ing

the

task

and

EXAM

is

the

name

that

would

be

used in

the

RES

command.

2.2.4 Sending Escape Sequences

Format:

CALL

PLOT55(13,ICHAR,[,ITBL))

This

command

reads a

number

that

you insert in place

of

ICHAR,

puts

an

<ESC>

character

(033 octal)

in front

of

it,

and

sends

those two characters to

the

VT55. This

sort

of

character

pair

is

called

an

"escape

sequence,"

and

it tells

the

VT55 to

do

the

following:

I.

Enter

escape mode.

2.

Perform a procedure specified by your choice

of

ICHAR.

3.

Return

to

the

previous

mode

(i.e., graphic or

alphanumeric)

when

the

procedure is finished.

ICHAR

is

a decimal integer.

The

values you

can

enter

for

ICHAR

are listed below along with

the

pro-

cedures

they

invoke:

ICHAR

value

65

67

72

74

Procedure

Move

cursor

up

one

line

Move

cursor

right

one

position.

Move

cursor

to

home

position.

Erase from

cursor

to

end

of

screen.

2-16

75

91

92

93

94

95

FOR

TRAN

Programming

Erase from cursor to

end

of

line.

Hold screen.

Release screen.

Copy from top

of

screen to cursor.

Start automatic copy.

Stop automatic copy.

NOTE

If

you

send an escape sequence that does not consti-

tute an executable command, the VT55

will

enter

escape mode and

then

automatically return to the

previous mode, without performing any operation.

The

same holds true if you use an ICHAR in the

range 93-95 and your VT55 has no hard copy unit.

Several

of

the PLOT55 forms, particularly the ones which are alphanumeric functions, work by sending

escape sequences to the VT55. For example, the forms

CALL PLOT55(11,,) and

CALL PLOT55(13,75,)

do exactly the same thing: erase from the cursor to the end of the line.

By

using escape sequences, you can simplify some operations considerably. Suppose you wanted to move

the cursor along the 20th line of text one character at a time. You could say

DO

11=1,80

J=I-l

1 CALL PLOT55(9,J,19)

But the same procedure

is

accomplished by saying

CALL PLOT55(9,0,19)

DO 11=1,80

1 CALL PLOT55 (13,67,)

Using ICMD=13 eliminates the computation

of

J=I-l

(which would be done

80

times),

but

more impor-

tantly, ICMD=13

is

a "simpler" command on the assembly language level and will be executed more quick-

ly.

Each

of

the

80

times ICMD=9

is

used, the ICMD=9 macro routine

is

called and

then

it calls seven addi-

tional routines to

home

the cursor, read

the

value

of

IX (even though, in this case, IX

is

the same

all

80

times), and repeatedly send escape sequences to move the cursor 20 lines down from the horne position.

Therefore, the execution speed

of

your program

will

nearly always benefit

if

you use

ICMD=

13

as

much

as

possible.

The

Hold Screen and Release Screen commands disable and reenable (respectively) the VT55's automatic

scrolling feature, that is, the feature that moves text up on the screen when you type more

than

24 lines.

2-17

FORTRAN

Programming

After you have displayed a graph on the screen, you may want to temporarily prevent the computer from

printing out the usual STOP message (or whatever your operating system normally displays at the end

of

a

FORTRAN program). Suppressing such messages

is

useful for appearance' sake and nearly always

desirable when you make a hard copy

of

the screen contents. The following sequence at the end

of

your

program

will

accomplish this task:

900 CALL PLOT55(9,79,23)

901

CALL PLOT55(13,91,)

902 PAUSE

903 CALL PLOT55(13,92,)

904

END

Statement 900 moves the cursor to

the

last position on the screen.

Then

Line

901

effectively 'freezes' the

screen so that the computer cannot display characters; the characters 'PAUSE--' are transmitted back to

the VT55, but because the scrolling

is

disabled they are not immediately displayed. The computer can still

read the VT55 keyboard, however, so that when you type a carriage return (or a RESUME command in

RSX-ll),

Statement 903

will

be executed, releasing the screen.

If

your VT55 has a built-in hard copier, you

can copy the contents

of

the screen (both graphic and alphanumeric) by pressing the orange COPY key on

the keyboard before typing the carriage return to release the screen. In any case, after releasing

the

screen,

you

will

have to push the orange SCROLL key a few times to scroll up the messages that were transmitted

while the terminal

was

in Hold Screen mode.

The escape sequence value

93

is

the programmed equivalent

of

manually pressing

the

COPY key on the

keyboard; it

will

create a copy

of

everything on

the

screen from the top up to the cursor position, including

graphic displays.

Remember

to position the cursor at

the

end

of

the screen--

CALL PLOT55(9,79,23)

before copying the screen.

The

escape sequence values 94 and

95

start and stop the automatic copy feature

of

terminals with a built-in

hard copier. Automatic copying should only be used with alphanumeric text; graphic displays

will

be dis-

torted

if

copied in this mode. When the VT55 receives a command to start automatic copying, it copies

the

contents

of

the screen beginning at the top and continuing up to

but

not including the line containing

the

cursor.

Then

one additional line

of

text will be copied each time you type a

LINE

FEED

on

the

keyboard.

Automatic copying

is

especially useful for creating permanent listings

of

programs and subroutines that

you write. This automatic mode can be started and stopped manually by holding down

the

SHIFT key

while you press the COPY key.

Example 6 contains a program that allows you to examine the effects

of

various escape sequences.

For more information on escape sequences, see the VT55-E,F DECgraphic Scope User's Manual (EK-

VT55E-

TM-OOO.

2-18

FOR

TRA

N

ProKramminK

ExampJe6

C THIS

PROGRAM

DEMONSTRATES

THE

USE

OF

ICMD

=

13,

C

WHICH

SENDS

"ESCAPE

SEQUENCES"

TO

THE

VT55.

C

C

THE

PROGRAM

WILL

READ

A TWO-DIGIT

INTEGER

THAT

C

YOU

TYPE

ON

THE

VT55

KEYBOARD.

THE

INTEGER

C

WILL

BECOME

AN

ARGUMENT

IN

A PLOT55

CALL

AND

WILL

C

PERfORM

SOME

OPERATION

ON

THE

VT55

SCREFN.

C

C

THE

INTEGERS

YOU

CAN

ENTER,

AND

THE

OPERATIONS

THAT

C W ILl, RESULT,

ARE

AS

fOLLOWS:

C

C 65 =

MOVE

CURSOR

UP

ONE

LINE.

C 67 =

MOVE

THE

CURSOR

ONE

POSITION

TO

THE

RIGHT.

C 72 =

MOVE

CURSOR

TO

THE

HOME

POSITION

(0,0)

C

69

=

ERASE

FRO~

CURSOR

TO

END

OF

SCREEN.

C 91 =

HOLD

SCREEN.

C 92 =

RELFASE

SCREEN.

C

C

AND,

IF

YOUR

VT55

HAS

A

HARD

COpy

UNIT

BUILT

IN,

C

C 93 =

COpy

FROM

TOP

OF

SCRfEN

TO

CURSOR.

C 94 =

START

AUTn~ATIC

PR!NT.

C 95 =

STOP

AUTOMATIC

PRINT.·

C

C

TO

STOP

THE

PROGP

AM,

TYPE:

99.

C

1 READ(S,2)

ICHAR

2

F~HMAT(I2)

IF

(ICHAR.E:(J.99) G(] TO 3

CALI,

Pl,UT"'5(13,ICf-lAR,O)

GO

T-Ci

1

3 END

2-19

CHAPTER 3

BASIC-PLUS PROGRAMMING

Four

BASIC-PLUS

functions

exist to aid VT55 graphic programming.

The

names

and

purposes

of

the

functions

are

as follows:

FNV5,

for

the

display

of

graphs,

markers,

vectors, vertical

or

horizontal lines,

and

shaded

graphs;

FNV6,

for

the

display

of

alphanumeric

characters

on

the

screen;

FNV7,

for

the

initialization

of

the

screen;

and

FNV8,

for

the

display

of

special "step" histograms.

Each

of

the

functions

is

used in

the

form:

D=

FNVx(arguments)

where

x

is

the

function

number

and

arguments

are

the

integers

or

character

strings you supply in a particu-

lar call.

After

a line

containing

one

of

these

functions

is

executed,

D will equal zero

if

the

function

executed

correctly.

If

some

error

is

detected

in

the

function,

control

is

immediately

returned

to

the

calling program

in

most

cases,

and

D

is

set

to -1. D

is

therefore

a kind

of

"condition code"

that

can

be

examined

after a

function call to

ensure

that

no

errors

have

occurred.

The

BASIC-PLUS definitions for

these

four functions

are

contained

in

the

file VT55.BAS.

The

function

definitions

in

VT55.BAS

must

be

added

to

every

BASIC-PLUS

program

you write for

the

VT55.

The

following dialog

shows

how

to

add

the

definitions

to

your

program

(the

underlined

statements

are

the

ones

that

you

would type).

READY

(The

numbered

lines for

your

program.)

APPEND

VT55

<CR>

(The

function definitions

are

added

to your program.)

3-1

BASfC-PL

US Programming

READY

RUN

or

RUNNH

<CR>

(The

program will

be

executed.)

Notice

that

there

is

no

line

number

for

the

APPEND

statement.

This procedure

will

add

the

lines in VT55.BAS to

the

end

of

your program, so

that

it will now contain

both

the

function definitions

and

an

END

statement.

Be

sure

t9 observe

the

following rules:

1.

Put an

END

statement

with line

number

32767 at

the

end

of

each program.

2.

The

file VT55.BAS contains BASIC-PLUS

statements

with line

numbers

from 20000 to 29999.

Avoid using

these

line

numbers

in your program.

3.

Similarly,

the

function definitions use

the

following "internal" variables to store graphic informa-

tion, so

they

should not be used

as

variables in your main program:

C9%:

Channel

number

for terminal.

CS$:

Output

buffer

for

alphanumeric

text.

C7%:

Current

graph

number.

07%: X value

of

origin.

Q7%: Y value

of

origin.

06%: Enable/disable memory.

Q6%: Enable/disable memory.

4.

The

following variables will be destroyed by

the

functions in VT55.BAS. Do not use

them

in your

program if

they

should

be

unchanged

after a call to

one

of

the

functions:

C9$:

Output

string for FNV6.

09%, Q9%,

OS%,

QS%,

09,

Q9,OS,

QS,

07,

A2, A7:

Temp~

rary "scratch" variables.

In addition to VT55.BAS, a

demonstration

program, DEM055.BAS, has

been

supplied in your BASIC-

PLUS kit. After you have read

and

understood

this manual, you should

run

DEM055

(preferably after list-

ing

the

program

on

a line printer) so

that

you can observe

the

functions in operation:

READY

OLD

DEM055

<CR>

READY

APPEND

VT55

<CR>

READY

RUNNH

<CR>

NOTE

See

the

introduction to

Appendix

C for instructions

on

loading

VT55.BAS from

the

distribution

medium

to your

system

disk.

3-2

BASIC-PL

US

Programming

3.1 FNV5,

THE

GENERAL

GRAPHIC

FUNCTION

Basic Call Format: D =

FNV5(AI

%,A2%,A3%)

Al

% can be

any

integer from

0%

to

13%

except

12%.

The

number

you insert in place

of

Al

% will select

the

procedure to be performed by

the

FNV5

call.

The

allowable values for

A2%

and

A3%

are explained later

for

each

procedure. An

error

return

(with D = -1) will result if

Al

%

is

less

than

0%.

3.1.1 Opening and Closing a VT55 for

Output

Call Format: D = FNV5(0%,A2%,A3%)

A2%,

an integer from

0%

to

63%,

is

the

terminal

number

of

the

VT55 terminal.

If

the

VT55 terminal

is

designated "KBI

:",

for example,

then

A2%

would be

1%.

Any time you make

A2%

greater

than

0%

in this

manner,

the

VT55 will be opened for

output

from your BASIC-PLUS program.

Note that

A2%

is

the

number

of

the

VT55, which

is

not

necessarily

the

same

as

the

number

of

the

terminal

used to

command

RSTS/E (that is,

the

terminal with which you logged

on

to

the

system). In fact, if conve-

nient

you should log on to a terminal

that

is

not a VT55, with

the

VT55 screen in plain view.

If

you log on

to KBI:

and

the

VT55

is

KB2:,

A2%

should be

2%

when

you

run

the

program. Now

the

VT55 will only

display

output

from

the

special functions FNV5, FNV6, FNV7,

and

FNV8, which are discussed in this

chapter. All

other

program output,

such

as

the

Question marks created by

INPUT

statements,

will appear

on your "command terminal,"

KB

I:. Therefore

the

VT55 screen,

and

any reproduction you make

of

the

screen,

will

be free

of

unwanted

messages.

A3%

is

the

logical

unit

number

opened

for

the

terminal and can be any integer from

1%

to

12%.

As long as

the

VT55

is

open,

the

logical unit

number

(or "channel") specified by

A3%

will be used for your program's

output.

To close

the

terminal

just

call

FNV5

again,

but

this time make

A2%

a negative integer (any negative value

will work). You should always

enter

a

0%

for

A3%

in a closing call, for example:

D = FNV5(O%,-5%,0%)

This call would close

the

terminal, closing

whatever

logical

unit

number

was opened by

the

previous com-

mand

opening

the

terminal. Closing your VT55 terminal also erases any graphic figure

on

the

screen, dis-

ables the graphic features you have chosen,

and

resets

the

starting coordinates (see

Al

% =

7)

to (0,0).

Therefore,

the

best practice in VT55 graphic programming

is

to make

the

opening call

(A2%

>

0%)

the

first FNV5 call and

the

closing procedure

the

last call in your program.

NOTE

Any alphanumeric

text that

was displayed by your program

will remain on

the

screen

whether

or

not

you close

the

VT55.

If you

enter

a logical

unit

number

outside

the

range

P/o-12%

or

a terminal

number

outside

the

range 0%-63%, an

error

return

will result

(D

= -0.

3.1.2 Graphic Display with FNV5

There

are eight forms

of

FNV5

that control graphic displays,

the

forms being selected by your choice

of

Al

%.

Pay particular attention to

the

order in which graphic

commands

are given,

as

illustrated in

the

exam-

ples that accompany

the

command

descriptions.

3-3

BASIC-PL

US

Programming

Select Graph

Number

(Al% =

1%)

Call Format: D = FNV5(1 %,A2%,0%)

A2%

should

either

be

0%

or 1 % and will select

the

graph

number

for

the

next

regular or

shaded

graph to be

plotted. This

number

will serve

as

the

"label" for

the

figure as long

as

the

figure

is

enabled.

A3%

is always

0%

in this call. Note that selecting this graph

number

is

only a labeling procedure (that is, it selects a regis-

ter to contain

the

graph plotting values) and does not display a graph. Displaying a graphic figure

is

a

three-

step process:

1.

Enable

the

figure (A 1 % =

2%).

2.

Select graph

number

(A 1 % = 1

%).

3.

Plot

the

figure

(AI

% =

3%).

Enable or Disable Graphic Figures (Al% =

2%)

Call Format: D = FNV5(2%,A2%,A3%)

This

command

is

the

"fundamental" form

of

FNV5, because all the graphic figures

must

be

enabled before

they will appear on

the

VT55 screen.

These

figures are all disabled at first, and once enabled they will re-

main so until specifically disabled.

A2%

and

A3%

tell which figures will be enabled or disabled, respectively.

The

following

numbers

can

be

used for

either

A2%

or

A3%:

1 % =

Enter

(or leave) graphic mode.

2%

= Enable (disable)

Graph

O.

4%

= Enable (disable)

Graph

1.

8%

= Enable (disable) Shaded

Graph

O.

16%

= Enable (disable) Shaded

Graph

1.

32%

= Enable (disable) horizontal lines.

64%

= Enable (disable) vertical lines.

128%

= Enable (disable) markers on

Graph

or Histogram

O.

256%

= Enable (disable) markers

on

Graph

or Histogram

1.

512% = Disable all figures and clear

the

graphic

memory

(A2% only).

When

you are enabling

and

disabling figures, you

can

either

put

single integers in

the

call for

A2%

and

A3%,

or you can substitute expressions

that

combine

any

or all

of

the

figures.

For

example,

D = FNV5(2%,1 %+2%+512%,8%)

would

do

the

following procedures:

1.

Erase any graphic figures left

on

the

screen

by previous programs (512%);

2.

Enter

graphic mode

and

enable

Graph

0

(1

%+2%);

and

3.

Disable Shaded

Graph

0 (A3% = 8%).

3-4

BASIC-PL

US

Programming

NOTES

1.

If

you

enter

the

same

number

for A2%

and

A3%,

the

corresponding

graphic figure will

be

enabled.

2.

Instead

of

an

expression

like 1 %+2%, you

can

enter

the

sum

of

several

numbers

to

enable

or disable fig-

ures,

such

as

24% to

refer

to

both

Shaded

Graph

0

and

Shaded

Graph

1.

However,

the

expression

form

will be

more

readily

understood

by

other

persons

reading

your

program.

3.

It

is

a good practice

to

always

include

the

number

512% in

the

A2% position

the

first

time

you

enable

graphic figures. Doing so will

eliminate

graphic dis-

plays left

on

the

screen

by a previous program.

4.

It

is

usually

undesirable

to

enable

a

graph

and

a

shaded

graph

with

the

same

graph

number

(e.g.,

Graph

0

and

Shaded

Graph

0).

5.

An

error

return

will

occur

(with D

set

to

-I)

if

the

sums

of

the

arguments

are outside

the

range

0%-

1023% (for A2%)

or

0%-511 % (for A3%).

Plot

Graph

(Al

% =

3%)

Call Formats: D =

FNV50%,A2%,A3%)

or

D =

FNV50%,A2%,0%)

The

first call

format

shown

is

used

to plot a

single

point

at

the

coordinates given by A2%

(0%

to 511

%)

and

A3%

(0%

to 235%).

For

example,

850

FOR

1%

=

1%

TO

511%

860 D =

FNV50%,I%,235%*RND)

870

NEXT

1%

will plot points

on

the

screen

with x values from 1 to 511

and

with y varying

randomly

between

0

and

235.

The

second

format

plots points with y values

from

an

array

called

V5.

You

must

dimension

V5

and

fill it

with y values

before

trying

to

plot

the

graphic figure.

V5

must

be

dimensioned

to

at

least -A2%-l%.

Other-

wise,

the

FNV5

call will

cause

a fatal

subscript

error.

Remember

that

BASIC-PLUS arrays begin with a

zero

subscript,

so

that

the

statement

DIM

V5(511)

creates

a

512-element

array.

For

example,

340

DIMENSION

V5(511)

350

FORI%=0%T0511%

360 V5(I%) = 118%+ 100%*SIN(I%150.)

370

NEXT

1%

380 D =

FNV5(1

%,0%,0%)

390 D = FNV5(2%,1 %+2%,0%)

400 D =

FNV50%,-512%,0%)

3-5

BASIC-PL

US

Programming

Lines 340-370 set up

V5

as a 512-element array and

then

fill

up

V5

with sine values.

Line 380 selects 0

as

the

label

of

the next graphic figure. Line 390 enters graphic mode and enables Graph

O.

Line 400 now plots

the

sine function in

the

form

of

a graph (Graph 0). Notice

that

A2%

is

a negative integ-

er. When

A2%

is

negative,

FNV5

plots a

number

of

y values from

V5

equal to

the

absolute value

of

A2%.

In

the

example shown here, 512 values (the entire contents

of

V5) will be used, so

the

sine function will

extend over the entire width

of

the

screen.

Example 1

NOTE

An error return (D = -1) will occur if

A2%

is

ever less than -512% (for the

second format). D

is

also set to

-1

if you plot a point with coordinates outside

the

screen area

(A2%

<

0%,

A3%

<

0%,

A2%

>

511

%,

or

A3%

> 235%).

THIS

SA~PLE

BASIC-PLUS

PROGRAM

USES

THE

FOUR

FUNCTION

STATE~ENTS

NEEDED

TO

PLOT

GRAPHS

~ND

SHADED

GRAPHS.

BEGIN

B~

CREATING

THREE

ARRA~S:

Al%

WILL

BE

THE

SINE

FUNCTION,

A2%

THE

COSINE

FUNCTION

AND

A3%

THE

EXPONENTIAL

FUNCTION.

100

DIM

A1%(499),A2%(499),A3%(499),V5(499)

110

FOR

1%

=

0%

TO

499%

120

Fl=I%/50.

130

f1=PI*Fl

140 Al%(!%) =

SIN(T1)*100+100

150

A2%(I%)

= COS(Tl)*100+100

IbO

A3%(I%)=EXP(Fl)

170 NExr

1%

180

INPUT

"WHAT

IS

THE

VTSS·S

KEYBOARD

NU~BER";I%

190 D = FNV5(O%,I%,1%)

!"CHANNEL

1"

ATTACHED.

lDEFINE

STARlING

POSITION,

SELECT

GRAPH

0,

!AND

PLOr

THE

SINE FUN:TIJN.

200 D =

FNV5(7%,O%,O%)

!STARf

AT

X=O.

210 D =

FNV5(2%,I%+2%,-O%)

!ENABLE

GRAPHIC

MJDE

ANO

lGRAPH

O.

220 D =

FNV5(1%,O%,O%)

lSELECT

GRAP~

O.

230 V5(1%1=Al%(I%)

FOR

1%=0%

TO

499%

lV5

IS

NJ~

THE

SINE FUNCfION.

240 D = FNV5(3%,-500%,0%)

!PLOT

THE

SINE

GRAPH.

2S0

INPUT

"C~NTINUE";C$

lPAUSE

AND

WAIT

FOR

CARRIAGE

RETURN;

THEN

!PUr

THE

CUSINE

FUNCTION

OM

THE

SCREEN,

TO~.

3-6

BASIC-PL

US

Programming

260 D =

FNVS(2,,4%,0%)

!ENABLE

GRAPH

1.

270 D = FNV5(1%,1%,0%) !SELECT

GRAPH

1.

280 V5(1%)=A2%(I%)

FOR

1%=0%

TO

499%

!CHANGE

V5

TO

COSINE.

290 D = FNV5(3%,-500%,0%) !PLOT

THE

COSINE

GRAPH.

300

INPUT

"CJ~TINUE";C$

!ERASE

BO~H

GRAPHS

(BY

DISABLING

rHE~)

AND

!PREPARE

TO

DISPLAY

SHADED

GRAPHS

INSTEAD.

310 D = FNV5(2%,8%+16%,2%+4%)

320

330

340

350

360

370

380

390

400

410

420

32767

!SHADED

GRAPH

0

~ILL

BE

fH~

EXPONENTIAL

AND

!SHADED

~RAPH

1

wILL

BE

fHE

COSINE.

D = FNV5(1%,0%,0%) !SELECT

SHADED

GRAPH

O.

V5(I%)=A3%(I%)

FOR

1%=0%

ro

499%

!VS

=

EXPON~NTIAL.

D = FNV5(3%,-500%,0%) !PLOT

THE

EXPJNENTIAL.

D = FNV5(1%,1%,0%) !SELECT

SHADED

GRAPH

1.

V5(I%)=A2%(1%)

FOR

1%=0%

ro

499%

!NOW

V5

= COSINE.

D = FNV5(3%,-500%,0%) !PLOT

THE

COSIN~.

1 N

PUT

" C

D.N

TIN

U E " ; C $

D = FNV5(2%,0%,16%)

!ERAS~

THE

CJSINE

SHADED

GRAPH.

INPUT

"CJNTINUE";CS

D = FNV5(2%,2%,B%)

!:HANGE

EXPO~ENTIAL

fJ

A

GRAPH.

!ENABLED

GRAPH

0

AND

~DISABLED

SHADED

GRAPH

O.

D =

fNV5(O%,-1%,O%)

!:LOSE

CHANN~L

1.

END

Plot Horizontal Line (AI % =

4%)

Call

Format:

0=

FNV5(4%,A2%,A3%)

A3% gives

the

y coordinate (0%-235%)

of

the

horizontal

line.

A2%

is

either

0%

or 1

%.

A2% =

0%

will erase

the

line at

the

y position

given

by A3%. A2% = 1 % will display

the

line.

Remember

that

the

horizontal

line

feature

must

have

been

enabled

previously

by

a call

such

as

0=

FNV5(2%,1

%+32%,0%)

NOTE

An

error

return

will

occur

if

you

try

to

display a line

off

the

screen

(A3% <

0%

or

A3% > 235%)

or

if

A2%

is

any

number

other

than

0%

or

1

%.

3-7

BASIC-PL

US

Programming

Plot Vertical Line (At% =

5%)

Call Format:

0=

FNV5(5%,A2%,A3%)

This command

is

very similar to

Al

% =

4%,

but

it uses a different combination

of

arguments to plot verti-

cal lines instead

of

horizontal lines.

In this call

A2%

is

the

x coordinate at which a vertical line will either be displayed or erased.

A2%

can take

values between

0%

and

511

%.

A3%

=

0%

will erase

the

line and

A3%

= 1 % will display

the

line.

Again, any values entered for

A2%

or

A3%

that

are not within the legal range will cause an error return.

Example

2:

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

32767

!THIS

PROGRAM

DRAWS

A "GRID"

ON

THE

SCFEEN

WITH

i

THr<:

VERTIC

AL.

AND

H01<1

ZONTAL

LINE

FI

GURES.

INPUT

"WHAT

IS

THE

VT55'S

TERMINAL

NUM8ER";T%

D = FNV5(0%,T%,1%)

!OPEN

AS

CHANNEL

1.

D = FNV5(2%,1%+512%+32%+64%,0%)

!GRAPHIC

MEMORY

CL~ARED;

GRAPHIC

MODE

AND

!BOTH

LINE

TYPES

ENABLED.

FOR

1%=2%

TO

502%

ST~P

10%

D = fNV5(5%,1%,1%)

NEXT

1%

!51

VERTI.CAI,

LINES

ARE

ON

THE

SCREEN;

PAUSE.

INPUT

"CONTINUE":C$

!TYPE A

CARRIAGE

RETURN

TO

CONTINUE.

FOR

1%=2%

TO

232%

STEP

10%

D = FNV5(4%,1%,I%)

NEXT

1%

124

HORIZONTAL

LINES

ADDED.

INPUT

"CONTINUE";CS

FOR

1%=2%

1'0

502%

S.TEP

10%

D = FNV5(5%,I%,0%)

NEXT

1%

1VERTICAL

LINES

ERASED.

D = FNV5(0%,-1%,O%)

ENn

!CLOSF

CHANNEL

1.

Plot

Markers

(At

% =

6%)

Call Format:

0=

FNV5(6%,A2%,A3%)

This

command

will display or erase markers on regular and shaded graphs plotted with

Al%

=

3%.

The

markers are

short

vertical line segments

that

will appear

on

the

graph at

the

x position you specify in

the

call.

A2%

is

the

x position

of

the

marker

(0%-511

%).

A3%

=

0%

will erase

the

marker, and

A3%

= 1 % will display it.

3-8

Example 3:

100

110

120

130

140

150

160

170

180

190

200

210

220

230

240

250

260

32767

BASIC-PL

US

Programming

NOTE

This

command

will not work properly unless

A2%

and

A3%

are within

the

stated ranges.

lTHIS

PRO~RAM

DEMONSTRATES

THE

USE

OF

MARKERS

ON

lGRAPHS

AND

HISTOGRAMS.

DIM

V5(499)

INPUT

"WHAT

IS

THE

VT55'S

TERMINAL

NUMBER":T%

o = FNV5CO%,T%,1\) lJPEN

FOR

OUTPUT

AS

:HANNEL

1.

V5(I%)=SINCPI*I%/SO.)*100.+100.

FOR

1%=0%

TO

499%

lV5

NOW

:ONTAINS

SINE

VALUES.

o = FNVSC2%,1%+SI2%+2%+128%,0%)

lRESET

THE

GRAPHIC

MEMORY

AND

1ENABLE

GRAPHIC

'MOoE,

GRAPH

0,

o = FNVSC7%,0%,0%)

o = FNV5Cl%,0%,0%)

o = FNV5C3%,-SOO%,0%)

INPUT

"CO~TINUE";C$

FOR

1%

=

SO%

TO

500%

STEP

SO%

D = FNVSC6%,I%,1%)

NEXT

1%

AND

MARKERS

FJR

GRAPH

0,

lSTART

AT

X=O.

ISELE:T

GRAPH

O.

lPLOr

THE

SINE

GRAPH.

SPUT

A

MARKER

ON

THE

INPUT

"CJHTINUE";CS

GRAPH

EVER¥

50 X UNITS.

lPAUSE.

D = FNVS(2%,8%,2%)

lENABLE

SHADED

GRAPH

0,

loISABLE

GRAPH

O.

INPUT

"COHTINUE":CS

!:HANGE

SINE

TU

SHADED

GRAPH.

lPAUSE.

D = FNVS(2%,0%,128%)

lREMOVE

THE

MARKERS,

D = FNV5(0%,-1%,0%)

BUT

LEAVE

THE

SHAPED

GRAPH.

!:LOSE

:HANNEL

1.

END

Define Starting Coordinates

(At

% =

7%)

Call Format: FNV5(7%,A2%,A3%)

This

command

defines new starting coordinates for vectors, graphs, and shaded graphs. For regular

and

shaded graphs,

the

Define Starting Coordinates

command

supplies a starting x coordinate for

the

figure,

without affecting

the

starting y coordinate. This

command

has no effect on single points plotted with

Al

%

=

3%).

Draw Vector

(At

% =

8%)

Call Format:

NOTE

An

error return will occur unless

A2%

is

in the

range 0%-511 % and

A3%

is

in

the

range 0%-235%.

D = FNV5(8%,A2%,A3%)

3-9

BASIC-PL

US

Programming

This

command

draws line

segments

called vectors, which

extend

from

the

starting

coordinates to a point

on

the

screen

given by

A2%

and

A3%.

A2%

is

the

x coordinate

of

the

vector's destination point

and

should

be

a

number

from

0%

to

511

%.

A3%

is

the

destination y coordinate, with allowable values

between

0%

and

235%. (An

error

return

will

occur

if

A2%

or

A3%

is

outside its legal range.)

If

you

have

previously

defined

starting coordinates

(AI

% =

7%)

when

you draw a vector,

the

vector will

begin at those coordinates.

Remember

that

the

"initialization" function

FNV7

(described later) resets

the

starting coordinates to (0,0).

The

Draw Vector

command

itself also resets

the

starting

coordinates to those of

the

destination point sup-

plied in your call. This feature allows you to "chain" vectors

together

to form geometric figures

or

other

straight-line drawings.

If

you want to draw a series

of

vectors

that

originate at

the

same

point, you

can

sim-

ply interweave Define Starting Coordinates

commands

with your Draw Vector

commands.

Vectors are

not

graphic figures, strictly speaking, because

they

do

not

have to

be

enabled. However, you

can (and

should)

label a series

of

vectors

that

make

a design

as

Graph

0

or

Graph

1,

and

Graphs

0

and

1 do,

of

course,

have

to be enabled.

Remember

that

you

cannot

draw a vector

that

is

perfectly vertical.

Example

4:

100

110

120

130

140

150

160

110

180

190

200

210

220

32767

!THIS

SAMPLE

PROGRAM

DEMJNSTRATES

THE

USE

!Of

VECTJRS,

WHI:H

CAN

BE

USED

T8

DR4~

!GEOMETRI: fIGURES

(A

DIAMOND

IN

THIS

CASE)

!AND

CAN

BE

LABELED

LIKE

GRAPHS.

INPUT

"WHAT

IS

THE

VT55'S

TERMINAL

NU~BER";T%

D =

fNV~(O%,T%,l%)

!DPE~

"CHANNEL

1."

D = fNV5(2%,1%+512%+2%+4%,O%)

!CLEAR

THE

SCREEN

Of

GRAPHIC

DISPLAYS,

ENTER

!GRAPHIC

MODE,

AND

ENABLE

BOTH

GRAPHS.

D = fNV5(1%,O%,O%) !SELECT

GRAPH

0.

D = FNV5(7%,100%,lOO%)

!(100,100)

IS

THE

STARTING

D = FNV5(8%,150%,150%)

D = fNV5(8%,200%,200%)

D = FNV5(1%,1%,O%)

POINT

OF

rHE

FIRsr

VECTOR.

!fIRST

VECTOR.

!SECJND V£CTJR.

!SELECT

GRAPH

1.

!THE

BOT

rOM

OF

THE

DIAMOND

wILL

D = FNV5(8%,150%,50%)

BE

GRAPH

1.

!THIRD VEcrOR.

D = fNV5(8%,200%,100%)

!FOURTH

(fINAL)

VECTOR.

!THE

DIA~OND

IS

COMPLETE.

I~Pur

"CJHTINUE";CS

!TYPE

A

CARRIAGE

RETURN

fJ

CONTINUE.

D = fNV5(2%,0%,4%)

!DISABL~

GRAPH

1.

lTO

DEMONSTRATE

THE

FACT

THAT

TWJ

SEPARAfE

!"GRAPHS"

ARE

BEING

DISPLAYED,

GRAPH

!1

(TH~

BOTTOM

Of

THE

DIAMOND)

WAS

ERASED.

D = fNV5(O%,-1%,O%)

!CLOSE

CHANNEL

1.

END

3-10

BASIC-PL

US

Programming

3.1.3

Alphanumeric

Display with FNVS

The

actual

output

of

alphanumeric

characters to

the

VT55

screen

is

done

with a separate function, FNV6.

However,

FNV5

contains

three

command

forms

that

are useful for

alphanumeric

display programming.

Position

Cursor

(At

% =

9%)

Call Format: D = FNV5(9%,A2%,A3%)

This

command

positions

the

cursor at a

new

point whose coordinates are given by

A2%

and

A3%.

A2%

is

the

number

of

character

positions from

the

left edge

of

the

screen

at which

the

cursor will appear.

A2%

can

therefore

take values from

0%

to

79%.

A3%

is

the

number

of

lines from

the

top

of

the

screen

at which

the

cursor will appear. Since

there

are 24

lines per

screen,

A3%

can

be

any

integer from

0%

to

23%.

Note

that

an

error

return

(D

= -1) will

occur

if

you

enter

values for

A2%

or

A3%

that

exceed

the

legal

ranges.

Note also

that

moving

the

cursor

with this

command

has no effect

on

graphic

or

alphanumeric

displays

on

the

screen.

Erase from

Cursor

to End

of

Screen

(At

% = to%J

Call Format: D = FNV5(lO%,0%,0%)

This

command

erases all

alphanumeric

text from

the

screen, starting at

the

cursor position

and

continuing

to

the

bottom

of

the

screen.

This

command

does not erase graphic figures from

the

screen,

nor

does it

change

the

cursor position.

Notice

that

the

call format

is

completely

standard

for this

command;

the

arguments

are always 10%,0%,

and

0%.

Erase from Cursor to End of Line

(At

% =

11

%)

Call Format: D =

FNV5(l

1

%,0%,0%)

This

command

is

very similar to

Al

% =

10%,

the

difference being

that

the

erasure

stops at

the

end

of

the

cursor's line instead

of

continuing

to

the

end

of

the

screen.

Note again

that

the

format

is

constant.

As with

the

previous

command,

the

status

of

graphic figures

and

the

cursor position are unaffected by

the

erasure.

3.1.4 Producing Hard Copy with FNVS

FNV5

can be used to

send

special instructions called "escape sequences" to

the

VT55 terminal. An escape

sequence

consists

of

the

ASCII code 155, which

is

interpreted

as

an

<

ESC>

character

in RSTS/E,

and

a

value you supply as

A2%

in

the

following call:

0=

FNV5(l3%,A2%,0%)

3-11

BASIC-PL

US

Programming

As

is

discussed in

the

VT55-E,F DECgraphic Scope User's Manual, escape sequences can be used to per-

form a variety

of

functions, including "cursor control" and screen erasure. Of course, these two types

of

control are provided by forms

of

the

FNV5 function, so that there

is

no

advantage to using escape se-

quences.

The

most helpful application

of

escape sequences

is

in producing a

paper-

copy

of

the screen display. This

procedure

is

only valid for VT55 terminals with a built-in hard copy unit;

the

same program can be run on

a terminal with no hard copier, but the hard copy commands (93%-95%)

will

be ignored.

Following

is

a list

of

values for

A2%

that

will

perform hard copy operations:

A2%

Value

91%

92%

93%

94%

95%

Procedure

Hold screen.

Release screen.

Copy from top

of

screen to cursor.

Start automatic copying.

Stop automatic copying.

The following example would copy

all

graphic and alphanumeric displays from the screen:

100

110

120

130

D = FNV5(9%,79%,23%)

D = FNV5(13%,91

%,0%)

D = FNV5(13%,93%,0%)

D = FNV5(13%,92%,0%)

!Cursor to bottom right.

!Hold screen.

!Copy entire screen.

!Release screen.

As

shown in Line 100, you have to first move the cursor to the bottom right corner

of

the

screen, because

the

copy operation

will

stop when the cursor

is

reached.

Line 110

will

"hold" the screen, temporarily preventing the display

of

further text or graphic

figures. While the VT55

is

in this mode,

the

computer

will

still read characters typed on

the

keyboard, but

will

not "echo" them, so they

will

not appear on the screen.

Line 120 now copies everything on

the

screen, from the topmost line to the cursor.

Now that

the

copy operation

is

finished,

the

screen

is

released by Line 130, which cancels

the

previous Hold Screen command. After the screen

is

released, you

will

have to press

the

SCROLL key a few times before you can continue. The SCROLL key

will

display any mes-

sages that were received while the screen

was

still being held, for instance, the READY mes-

sage that tells you the system

is

ready for new commands.

If

you have a screen display consisting entirely

of

alphanumeric text, you can use the automatic copy com-

mands to produce "line printer" type listings. When the VT55

is

in automatic copy mode, it

will

first copy

everything up to but not including the line containing

the

cursor;

then

it

will

copy one additional line each

time you push the

<LINE

FEED>

key on the keyboard.

The

following example shows a programmed

automatic copy operation:

100 D = FNV5(9%,0%,0%) !Cursor to home position.

11

0 D = FNV5

(1

3%,91

%,0%)

!Hold screen.

120 D = FNV5(13%,93%,0%) !Start automatic copying.

130 INPUT A$

!A LINE

FEED

WILL COPY

ONE

MORE

!LINE.

THE

LETTER'S'

WILL STOP

!AUTOMA TIC COPYING.

3-12

140

150

160

BASIC-PL

US

Programming

IF

A$='S'

GOTO 160

GOTO 130

D = FNV5(I3%,95%,0%)

!Type S to stop.

!Read

the

next

character.

!Stop automatic copy.

This example will read each line feed

that

you

enter

to copy lines.

It

will keep

the

terminal in

automatic copy mode until you

enter

the

character

S.

NOTES

1.

Automatic copying should only

be

used

with alphanumeric text.

The

hard copy

of

a

graphic figure will be distorted

if

produced

in line-by-line fashion.

2.

The

screen

will temporarily go blank while a

copy operation

is

in progress.

3.

The

copy operation can

be

manually started

any time the program pauses by simply

pressing

the

orange COPY key

on

the

VT55

keyboard. Similarly, pressing

the

COPY key

while holding down

the

SHIFT key will

both start and stop automatic copying.

3.2 FNV6,

THE

TEXT OUTPUT FUNCTION

Call Format: D = FNV6(N%,CI$)

FNV6

displays a character string on

the

VT55 screen.

The

string will appear with

the

first character at

the

cursor position, so

that

FNV6

is

often used in combination with

the

"alphanumeric" forms

of

FNV5, which

control

the

cursor position and

the

erasure

of

characters (see Section 3.1.3).

As

the

format shows, there are only two arguments for FNV6, both

of

which are required at all times.

CI$,

a string variable, stores

the

text

that

you wish to display

on

the

screen.

CI$

can

be

either a regular or

subscripted variable,

depending

on

the

type

of

display you are designing. A regular string variable can ac-

cept a string

of

80 characters, which

is

the

maximum

width

of

a line

of

characters on

the

screen. Therefore,

you can use regular variables when

the

string will

be

displayed horizontally. Vertical displays require ei-

ther

subscripted variables, so

that

one

element

can be displayed per line, or alternatively,

the

use

of

the

BASIC-PLUS function MID, which selects "substrings" from a regular character string variable and there-

by allows you to address individual characters or groups

of

characters in a string. Example 5 shows how

MID

can

be

used to

put

a vertical label

on

a graph.

3.3 FNV7,

THE

INITIALIZATION FUNCTION

Call Format:

D=FNV7

This simple function (notice

that

there

are no arguments) resets

the

screen to an "initial state,"

that

is:

1.

The

starting coordinates are reset to the point (0,0), the lower left corner

of

the

screen;

2.

All graphic figures are erased from

the

screen, leaving only alphanumeric text;

3-13

BASIC-PL

US

Programming

3.

The

internal

variables

06%

and

Q6%,

which

store

information

about

the

graphic figures, are reset

to 0,

disabling

all

graphic

figures;

and

4.

The

terminal

is

returned

to

alphanumeric

mode.

All

four

of

these

initializations

can,

of

course,

be

performed

by

FNV5

calls,

but

FNV7

is

a

more

direct

and

simple

method.

Therefore,

it

is

good practice to call

FNV7

immediately

after

opening

the

terminal

(see

Example

5).

Example

5:

NOTE

FNV7

should

not

be

used

in

the

middle

of

a

program unless you

want

to totally

eliminate

the

ef-

fects

of

previous

FNV5

calis.

!THIS

SAMPLE

PROGRAM

USES

SEVERAL

FORMS

OF

F~VS

!

AS

WELL

AS

THE

ALPHANU~E:RIC

Fll~,ICTION

FNV6

AND

!THE

INITIALIZATION

FUNCTION

fNV7.

90

DIM

V5(499)

100

INPUT

"WHAT

IS

THE

VT55'S

TERMINAL

NUMBER":T%

110 D = FNV5(0%,T%,1%)

!OPEN

"CHANNEt

1."

120 D =

FNV7

!FNV7

CLEARS

THE

SCREEN

OF

GRAPHIC

FIGURES

AND

!RESETS

THE

STARTING

COORDINATES

TO

(0,0).

130

GOSUB

1000

!THE

SUBROUTINE

AT

LINE

1000

CLEARS

ANY

STRAY

TEXT

!FROM

THE

SCREEN.

140 D = FNV5(9%,0%,12%)

!PUT

THE

CURSOR

AT

THE

BEGINNING

OF

LINE 12

AND

!DISPLAY A

MESSAGE.

150

160

170

180

190

200

210

C9S='TYPE A

CARRIAGE

o = FNV6(58%,C9S)

INPUT

"CONTINUE";C$

D = FNV5(9%,44%,12%)

D = FNV5(11%,0%,0%)

INPUT

"CONTINUE";CS

GOSUB

1000

RfTURN;

SYMBOLS

WILL

VANISH:

1234567890(>+'

DISPLAY

THE

CHARACTERS.

PAUSE

FOR

CARRIAGE

RETURN.

REPOSITION

CURSOR.

ERASE

SYMBOLS.

PAUSE.

CLEAR

SCREEN.

.!

liSE

FNV6

TO

I,ABF:L.A

GFAPH.

,

-

220

0.=

FNV5(2%,1%+2%+32%+64%+128%,0%)

230

PRINT 'TYPE X

AXIS

LABEL

(UP

TO

80 CHARACTERS):'

240 D = fNV5(9%,0%,2%) !POStTION

CURSOR.

250

INPUT

X1S

260

GOSllB

1000

!CLEAR

SCREEN.

270 PRINT 'TYPE Y

AXIS

LABEL

(UP

TO

24 CHARACTERS):'

280 D = FNV5(9%,O%,2%)

290

INPUT

Y1S

3-14

BASIC-PL

US

Programming

300

GOSUB

1000

lCLEAR SCREEN.

310

FOR

1%=0%

TO

499%

320

V5(I%)

=

SINCPI*I%/50.)*100.+100.

lV5=SINE.

330

NEXT

1%

340

0 =

FNV5C5%,0%,1%)\D

= FNV5C4%,1%,0%) 10ISPLAY AXES.

350

0 =

fNV5C9%,0%,23%)

lCURSOR

TO

BOTTOM

LINE.

360

0 =

FNV6(80%,X1S)

lDISPLAY X AXIS LABEL.

370

FOR

1%

=

1%

TO

LEN(Y1S)

380

L2%

= 1%-1% !L2%

IS

A LINE COUNTER.

390

0 = FNV5(9%,0%,L2%1

!POSITION

CURSOR

FOR

1 CHARACTER.

400

0 =

FNV6(1%,MID(Y1S,I%,1%»

!DISPLAY

ONE

CHARACTER.

410

NEXT

1%

lCONTINUE UNTIL Y AXIS

LABEL

IS

COMPLETE.

420

D =

FNV5(1%,0%,0%)

lNOW

DISPLAY

THE

SINE

FUNCTION.

430

0 =

FNV5(3%,-500%,0%)

440

0 =

FNV5(9%,40%,0%)

450

INPUT

"X

POSITION

OF

MARKER";Ml%

460

0 =

FNV5(9%,40%,0%)

470

0 =

FNV5(11%,0%,0%)

lERASE

THE

PREVIOUS MESSAGE.

480

0 =

FNV5(6%,Ml%,1%)

lPUT A

MARKER

AT

X=M1%.

1000

1010

1020

1030

32767

!THIS

SUBROUTINE CLEARS

o = FNV5(9%,O%,0%)

o = FNV5(10%,O%,O%)

RETURN

END

THE

SCREEN.

!CURSOR

TO

HOME

POSITION.

!ERASE SCREEN.

3.4 FNV8,

THE

STEP

HISTOGRAM

FUNCTION

Call

Format:

D = FNV8(N%,O$,Q$)

FNV8

creates step histograms,

or

vertical

bar

graphs, from

the

array V5. V5

must

be

properly

dimensioned

and

filled with values in

the

main

program,

and

you

must

select

either

Shaded

Graph

0

or

Shaded

Graph

1

before

the

FNV8

call.

After

these

preliminaries, a call to

FNV8

has

the

following results:

1.

The

first

N%

values

are

selected from V5.

2.

The

screen

width (512 x units)

is

divided

into

N% equal-sized segments.

3.

N%

horizontal vectors are drawn,

each

with a width

of

512%/N%.

The

screen

area

beneath

each

vector

is

then

shaded to

create

N%

vertical bars.

4.

The

horizontal vectors

have

been

enabled

separately as

Graph

0 (or 1

if

you selected

that

number

before

the

FNV8

call).

The

entire

step

figure is

then

enabled

as a Shaded

Graph

with

the

same

number

as

the

vectors' graph

number.

Because

of

this dual use

of

the

same

graph

number,

the

envelope

of

the

step

histogram

(that

is,

the

vectors) will

have

a

higher

display

intensity

than

the

rest

of

the

figure. As was

mentioned

previously (Section

3.1.2),

the

effect

of

using

the

same

graph

number

twice

is

usually undesirable,

although

it adds clarity to

the

final figure in this case.

5.

The

different

bars will

have

heights equal to

the

corresponding

"y

values" selected from V5.

3-15

BASIC-PL

US

Programming

6.

Finally, the character strings you have supplied for

0$

and Q$ are displayed as labels for

the

hori-

zontal and vertical axes

of

the

histogram, respectively.

0$

can be a string

of

up to 80 characters,

and Q$

as

many

as

24

characters.

Consider the following calling sequence:

10

DIM V5(I9)

20

D =

FNV5(I

%,0%,0%)

!Select graph number.

30

FOR

1%

=

0%

TO

19%

40

V5(1%)

=

10%*(1%

+ 1

%)

!Fill

V5

with integers.

50 NEXT

1%

60

D = FNV8(20%, 'FIRST

20

INTEGERS', 'INTEGERS TIMES

TEN')

This fragment would display twenty bars, each about

25

x units wide

(512%120%).

The

first bar would be

10

y units tall and

the

twentieth bar, 200 units.

Besides being a useful function in its own right, FNV8

is

a good model for new functiOns you can create for

your special needs. BASIC-PLUS has easy procedures for writing new functions, and your growing experi-

ence with VT55 programming

will

allow you to combine FNV5, FNV6, FNV7, and FNV8 to create in-

creasingly powerful graphic commands. Appendix C

of

this manual suggests

other

functions that you may

find useful.

3-16

APPENDIX

A

FORTRAN

(PLOT55)

ASSEMBLY

AND

LINKING

PROCEDURES

PLOT55

is

supplied in both source and object form.

If

the

PLOT55 file in your kit

is

labeled PLOT55.MAC,

it

is

a

MACRO-ll

source file and must be assembled (Section

At)

and

then

linked to each program you

write that contains PLOT55 calls (Section

A2).

If

you are given a preassembled object file (PLOT55.0BJ),

you only have to follow the linking procedures for your operating system.

A.I

ASSEMBLING

AN

OBJECT FILE

This procedure

will

translate the MACRO-II assembly language code in PLOT55.MAC into binary ma-

chine instructions. You must do this job and

the

linking procedure shown in Section

A.2

before your pro-

gram

will

work.

Suppose you are using a PDP-1l/34 computer with a pushbutton console, two RK05 disk drives, and

the

R T

-11

operating system.

1.

Put

the

DECpack containing PLOT55.MAC in Disk Drive 1 (DKI:) and close the door. Push

the

switch on the disk drive panel from LOAD to RUN.

2.

In the same manner, load your "system disk" into Drive 0 (DKO:). This disk should contain an RT-

11

operating system, the MACRO-II assembler (MACRO.SA V), and the System MACRO Library

(SYSMAC.SML).

3.

Start the R T

-11

system by these procedures:

A Push the button marked CTRL on the PDP-1l/34 and hold it down while you press the

BOOT

button. The terminal

will

display a list

of

octal numbers followed by the $ symbol.

B.

Type the two-letter device code on the terminal that represents

the

storage device containing

your system. Because

we

are using RK05 disks in our example, you would type the under-

lined symbols:

077776. 012456. 127645

$DK

<CR>

C.

The computer

will

read

the

bootstrap from your system in Drive

0,

start the

RT-ll

system,

and display the system title, for example:

RT-ll

FIB

V02C

Then

the

system

will

display a period

(.)

at the left margin, meaning that it

is

ready to accept

system commands.

A-I

FORTRA

N

(PLOT55)

Assembly and Linking Procedures

4.

Assemble the PLOT55 object file by typing the underlined parts

of

these lines:

.R MACRO < CR >

*PLOT55=DKl:PLOT55

<CR>

*TC

The second asterisk shown above

will

not appear until the assembly

of

the

object file

is

complete. To exit

from MACRO, you

then

type "Control C" by holding down

the

CTRL key on the terminal while you type a

C.

At this point PLOT55.0BJ has been created on Disk

O.

If

you want the new object file to be placed on

Disk I, type DKI :PLOT55 on both sides

of

the equal sign rather than only the right side.

If you are using a different computer:

Follow the customary procedures for bootstrapping the system and

then

begin with Step 4

of

the previous assembly procedure.

If

you are using an

RSX-ll

system:

When your PLOT55 source

is

on a DECtape (DT:) or RK disk (OK:):

>MOU

DK:(or DT:)PLOT55

<CR>

>MAC

PLOT55~K:(or

DT:)[200,200]PLOT55

<CR>

When your source

is

on magnetic tape:

>FLX

SY:/RS=MT: (or MM:) [200,200] PLOT55.MAC/OOS

<CR>

>MAC

PLOT55=PLOT55

<CR>

Both procedures

will

assemble PLOT55.0BJ on the system device, placing

the

object file in

the VIC under which you have logged on to the system.

The

additional FLX command

is

necessary in the second step because the magnetic tape

is

in DOS-II format.

If you are using an lAS system:

When your PLOT55 source

is

on a DECtape (DT:) or

RKdisk

(OK:):

PDS>MOUNT

<CR>

DEVICE? OK: (or DT:)

<CR>

VOLUME-ID? PLOT55

<CR>

PDS>MACRO

OK: (or DT:) [200,200]PLOT55

<CR>

When

your PLOT55 source

is

on magnetic tape:

PDS>

MOUNT IFOREIG N/OVERRIDE:

VOLUMEID<CR

>

DEVICE? MT: (or MM:)

<CR>

VOLUME-ID? PLOT55

<CR>

PDS>COPY

<CR>

FROM? MT: (or MM:) [200,200] PLOT55.MAC/OOS

<CR>

TO?

*.*

<CR>

--

PDS>

MACRO PLOT55

<CR>

After either procedure, the assembled file PLOT55.0BJ

will

exist on the system device with

the same UIC under which you logged on to lAS.

A-2

FOR

TRA

N (PL0T55) Assembly and Linking

Procedures

If

your storage devices are not RK05 disks:

The

only change

is

the

two-letter code for

the

device. Standard codes include:

SY:

DB:

=

DX:

DT:

CT:

DP:

MT: =

MM:=

Any device identified beforehand as the system device for your installa-

tion.

RP04, RP05, or RP06 disk drive.

RXOI "floppy disk" drive.

DECtape drive.

DECcassette tape drive

(RT-ll

only).

RP02/03 disk drive.

TUI0

magnetic tape drive.

TJU16 magnetic tape drive.

A.2 LINKING AN

OBJECT

FILE TO YOUR

PROGRAM

A.2.t

Procedure for

RT-ll

Users

Type

the

underlined parts

of

the following R T

-11

commands:

.RLINK<CR>

*program=object,PLOT55IF

<CR

>

*lC

where "program"

is

the

name

you want for

the

finished program, and "object"

is

the

name

of

the

object file

for

that

program (that is,

the

output

of

the

FORTRAN

compiler). PLOT55

is

the

object file

that

was

either

supplied in your software kit or was produced by

the

assembly procedure in Section A.t.

The

"IF"

switch

tells the

LINK

program

that

your program

is

using

FORTRAN

statements

and library functions.

LINK

will

look for

the

FORTRAN

library (FORLIB.OBJ)

on

the

system disk.

If

FORLIB

is

on

some

other

stor-

age device, follow

the

PLOT55

name

with ",dc:FORLIB" instead

of

the

IF,

where dc:

is

the

code for

the

device containing FORLIB.

LINK

will print

the

second asterisk shown to indicate

that

the

linkage was successful. To exit from LINK,

type

CTRL

C.

Your VT55 program can now

be

run

by typing

.R program <

CR

>

A.2.2 Procedure for

RSX-ll

Users

Type

the

underlined part

of

the

following

command

in response to

the

prompt

symbol

(»:

>TKB

task=objectlFP,PLOT55

<CR>

The

name

you insert for "task"

will

be

assigned to

the

finished, executable task image

of

your

FORTRAN

program.

The

label "object" refers to

the

compiled form

of

your program, and "PLOT55"

is

actually

PLOT55.0BJ,

the

object file

that

was

either

supplied in your software kit or created by

the

assembly pro-

cedures in Section A.t.

The

IFPswitch

means

that

the

Floating Point Processor will

be

used.

Notice

that

the

command

line has

no

references to a

FORTRAN

library.

The

task builder will expect

SYS-

LIB to contain

the

FORTRAN

object code

needed

by your program.

If

SYSLIB

is

not

on

your disk, or

if

A-3

FORTRAN

(PLOT55) Assembly and Linking Procedures

you are using a separate

FORTRAN

library, you have to state

the

exact

name

and

location

of

the

library in

the

TKB command, for instance:

> TKB task=objectlFP,PLOT55,DKI : FORLIB/LB

<CR>

Regardless

of

the

particular TKB

command

you use,

the

prompt symbol will reappear

when

the

task image

is

ready. You are

then

ready to

run

your VT55 program by typing

>RUNtask

<CR>

If

you received the binary file PLOT55.0BJ in your kit rather

than

the

source file PLOT55.MAC, you

should transfer

the

object file to your UIC before

running

TKB. Use

the

RSX-ll

MOU

and

FLX

com-

mands described in Section A.I.

The

only change required

is

making

the

file

name

extension .OBJ instead

of.MAC.

A.2.3 Procedure for lAS Users

Type

the

underlined part

of

the

following

command

in response to

the

Program Development System's

prompt symbol:

PDS>LINK/TASK:task

object PLOT55

<CR>

where task

is

the

name

you want for

the

finished, executable task image

and

object

is

the

name

of

the file

containing the compiled form

of

your main program. PLOT55 represents

the

file PLOT55.0BJ, which was

either supplied in your software kit or created by a previous assembly

of

the

file PLOT55.MAC.

The

PDS>

prompt symbol will reappear

when

the

task

is

finished and ready to run.

The

lAS

LINK

utility assumes

that

the

Floating Point Processor will

be

used.

When

the

LINK

program

is

finished building

the

task,

the

task can

be

executed with

the

command

PDS>RUN

task<CR>

If

you received

the

binary file PLOT55.oBJ in your kit

rather

than

the

source file PLOT55.MAC, you

should transfer PLOT55.0BJ to your UIC before

running

LINK. Use

the

same lAS

MOUNT

and COPY

commands

described in Section A.I, changing

the

.MAC extension in

the

COPY

command

to .OBJ.

A-4

APPENDIX

B

SUGGESTED

PLOT55

APPLICATIONS

This appendix contains examples

of

FORTRAN subroutines that combine various PLOT55 calls to

achieve "higher level" functions. For example, your use

of

a VT55 might require

the

display

of

a large num-

ber

of

graphs, in which case you can avoid a large

number

of

PLOT55 calls in your program by following

the techniques suggested in this appendix.

Not

all

of

these routines would be needed by every user, and there

is

rarely any saving in execution speed,

because

the

routines result in just about

the

same

number

of

PLOT55 calls as would occur anyway.

The

advantage

of

subroutines

is

that they allow you to define, debug, and save an entire procedure, which can

then

be reused

as

often

as

necessary without the risk

of

new programming errors.

You can try the routines suggested in this appendix by compiling and linking

them

as

you did for PLOT55.

You may find that they can be used

as

they are shown here or that some additional modifications would

make

them

more applicable to your needs.

Notice that these subroutines use the four-argument form

of

PLOT55.

The

fourth argument

is

the 16-ele-

ment

array

1ST

AT, and it

is

placed in a common area labeled STATUS.

The

use

of

such a common status

table allows you to share the same status information between any

number

of

routines. Within each rou-

tine, individual elements

of

1ST

AT can be examined and changed to control

the

overall status

of

the

VT55

display. For example, the element ISTAT(8) stores the current graph number; ISTAT(8) equals 0 if Graph

o

is

in use and 8 if Graph 1

is

in use. The full list

of

status table elements and their uses

is

as

follows:

ISTAT(l):

ISTAT(2):

ISTAT(3):

ISTAT(4):

ISTAT(5):

ISTAT(6):

ISTAT(7):

ISTAT(8):

ISTAT(9):

ISTAT(10):

ISTAT(l1):

ISTAT(12)-

ISTAT(16):

B.t

INITIALIZATION

Logical unit

number

of

terminal.

Event

flag

number

to be used.

X value

of

origin.

Y value

of

origin.

Work register (do not change contents!).

Work register.

Graphic status (holds the current total from IENAB).

o

if

Graph 0

is

in use; 8

if

Graph

1.

Graphic mode switch (O=Off, I=On).

Work register for vectors (do not change!).

Character count (RSX

-11

only).

Character output buffer (RSX -11).

In

most applications, it

is

useful to have a routine such

as

the

one shown here that

will

return the VT55 to

some initial state

as

preparation for running a new program.

SUBROUTINE

INIT

COMMON/ST ATUS/ISTAT(16)

DATA ISTAT/16*01

B-1

SUf.{f~ested

PLOT55

Applications

CALL PLOTSS(13,72"ISTAT)

CALL PLOTSS(l3,74"ISTAT)

CALL

PL0T5S(2,1

+SI2"IST

AT)

RETURN

END

The

statement

CALL

INIT

will first clear all

alphanumeric

text

from

the

screen

and

then

will disable all

graphic figures, clearing

the

screen

of

graphic displays as well.

INIT

is

therefore

a good example

of

a

"starting routine" for a graphic program.

B.2

GRIDS

AND COORDINATE AXES

2

3

4

SUBROUTINE

GRID(IDX,IDY)

COMMON

1ST

A TUS/IST A

T(l6)

CALL

PL0T55

(2, 1 + 32+64"IST AT)

00

1

1=I,SI2

CALL

PLOTS5(5,I-l,0,ISTAT)

DO

21=1,236

CALL

PLOT55 (4,0,I-l,IST AT)

00

3

I=I,512,IDX

CALL

PLOT55(5,I-l,I,ISTAT)

00

4 1=1,236,IDY

CALL

PLOT55(4,I,I-l,IST AT)

RETURN

END

The

numbers

you supply for

lOX

and

lOY

in a

CALL

GRID

statement

will

be

the

spacing in

screen

units

between

the

vertical

and

horizontal lines, respectively.

GRID

will

therefore

display a rectangular grid

on

the

screen, which can be superimposed

on

other

figures

such

as graphs

and

histograms.

If

GRID

is

called

several times in

the

same

program, it will erase any old grid before displaying a new one.

To display only a y axis at

the

left edge

and

an

x axis at

the

bottom

of

the

screen, use a

CALL

GRID

state-

ment

with

lOX

equal to any integer greater

than

S11

and

lOY

any

integer greater

than

23S.

The

markers described in

Chapter

2 (ICMD = 6) are

the

best way to

mark

off

a graph in

the

x direction.

You may, however, want to

put

a vertical scale

on

a graphic figure

as

well. With a routine

such

as

GRID,

you could, for example, scale

the

screen

vertically in

increments

of

20 units by calling

GRID

with

lOX>

S11

and

lOY

=

20.

B.3

GRAPH

PLOITING

ROUTINES

The

examples in this section suggest "canned" procedures for

the

most

common

use

of

VTSS: plotting

graphs or

shaded

graphs

of

already

computed

data.

SUBROUTINE

GRAPH

(N

,IARRA

Y)

COMMON

1ST

ATUS/IST

AT(l6)

DIMENSION

IARRAY(SI2)

NUMBER=IST

AT(8)/8

CALL

PLOT5S(7,O,O,IST AT)

CALL

PLOTSS(8,S12,0,ISTAT)

CALL

PLOTSS(2,1

+(NUMBER+

1)*2,(NUMBER+

1)*10,ISTAT)

CALL

PLOTSS(3,-

N,IARRA

Y,IST AT)

CALL

PLOTSS(l,l-NUMBER"ISTAT)

RETURN

END

B-2

Suggested

PL0T55

Applications

When

you write a CALL

GRAPH

statement, a graph will appear that displays

the

first N points from IAR-

RA

Y (where

IARRA

Y

is

some integer array that you have filled with the points you want to display).

This particular

GRAPH

routine also switches automatically between Graph 0 and

Graph

1,

in

the

follow-

ing manner:

1.

After a CALL

INIT

statement, CALL

GRAPH

will use

Graph

0 to plot

the

array you supply.

2.

If

GRAPH

is

called a second time in

the

same program (without calling

INIT

again),

the

second

graph

will

appear as Graph

1,

superimposed on Graph

O.

3.

If

GRAPH

is

called a third time,

the

new graph will be

Graph

0 again, erasing

the

old

Graph

0

but

leaving

Graph

1 on

the

screen.

The

erasure

of

the old graph

is

done

by drawing a vector from

the

point (0,0) to

the

point (512,0), which

is

a short method for resetting

all

the

y values

of

a graph to

O.

4.

Consequently,

all

even-numbered

calls to

GRAPH

will create a new

Graph

1,

and odd-numbered

calls a new

Graph

O.

SUBROUTINE SHADOW

COMMON/STATUS/lSTAT(l6)

NUMBER=IST

AT(S)/S

CALL PLOT55(2,1+(1-NUMBER)*S+S,(l-NUMBER)*2+2,ISTAT)

RETURN

END

CALL SHADOW converts a regular graph to a shaded graph.

If

you want to "shade" a particular graph, you

must

call SHADOW immediately after calling

GRAPH,

for

example,

CALL

GRAPH

(500,SINE)

[Plot the sine function on

Graph

0.]

CALL SHADOW [Shade

Graph

0.]

CALL GRAPH(500,COSINE) [Graph

1.]

CALL SHADOW [Shade

Graph

1.]

Shading

is

a useful practice for distinguishing two graphs. For example,

the

sine and cosine graphs have

exactly the same shape, and so are

much

easier to tell apart if

one

of

them

is

shaded.

SUBROUTINE BARS(N,IARRA Y)

COMMON/ST ATUS/IST

AT(l6)

DIMENSION IBAR(236,2),IARRAY(512)

NUMBER=IST

AT(S)/S

CALL PLOT55(7,0,0,ISTAT)

CALL PLOT55(S,512,0,ISTAT)

CALL PLOT55 (2, 1 +

(NUMBER

+

1)

*2"IST A

T)

WIDTH=512.1FLOAT(N)

DO

1

I=I,N

IBAR(I,l)=I*WIDTH

IBAR(I,2)=IARRAY(I)

CALL PLOT55 (7,0,IBAR(l,2),ISTAT)

DO

2

I=I,N

B-3

2

Suggested PLOT55 Applications

CALL PLOT55(S,IBAR(I,l),IBAR(I,2),1STAT)

CALL PLOT55 (7,IBAR(I,l),1BAR(I+ 1,2),ISTA

T)

CALL PLOT55 (1,1-NUMBER"IST A T)

CALL SHADOW

RETURN

END

BARS creates a special type

of

shaded graph called a step histogram, or "bar graph." BARS

will

display N

vertical shaded bars

of

width 512/N on the screen."The bars

will

have heights equal to the first N elements

of

IARRA

Y.

This example

of

a bar graph routine has the same mechanisms

as

the previous

GRAPH

rou-

tine for switching between Graph 0 and Graph 1 and for erasing old graphs (the "zeroing vector").

B.4 LABELING A GRAPHIC DISPLAY

3

4

SUBROUTINE LABEL(IXLABL,IYLABL)

COMMON/ST ATUS/IST AT(16)

LOGICAL*1IYLABL(24)

CALL PLOT55 (9,0,23,1STAT)

CALL PLOT55 (12"IXLABL,ISTAT)

00

3 1=1,24

IF(IYLABL(I).EQ.O) GO TO 4

CALL PLOT55(9,0,1-1,ISTAT)

CALL PLOT55 (12, 1 ,1YLABL(I)

,1ST

A T)

CALL PLOT55 (9,0,23,ISTAT)

CALL PLOT55 (13,91"ISTAT)

PAUSE

CALL PLOT55 (13,92"IST AT)

RETURN

END

LABEL

will

use the two strings you

enter

for

IXLABL and IYLABL

as

axis labels for the x and

yaxes,

respectively. Note that the labels you supply must be enclosed in single quotation marks (') to identify

them

as

alphanumeric strings in

FORTRAN

symbology.

The

x axis label

will

appear on the very bottom line

of

the screen, below the x axis.

It

can be up to 80

characters long (including spaces).

The

y axis label

will

read from top to bottom (one letter per line) and

will

appear in "Column

0,"

the left-

most column

of

the screen. This column

is

to the left

of

a vertical line at x =

0,

because the graph area

of

the VT55

is

slightly smaller

than

the alphanumeric area.

The

y axis label can be up to 24 characters long,

including spaces.

Notice that the LABEL routine sends two escape sequences.

The

first one holds

the

screen to prevent the

STOP message from interfering with

the

display.

The

screen

will

not be released until you type a carriage

return (or a "RESUME task" command in RSX

-11

systems).

If

you

will

be using lAS, replace the PAUSE

statement with the statement pair

READ(5,5)KR

5 FORMA T(I2)

The

PAUSE statement

will

be ignored in an lAS execution. (To bring

the

terminal back to a completely

normal state after this sort

of

procedure, press

the

orange SCROLL key until

the

STOP message and the

operating system's prompt symbol reappear.)

B-4

Suggested

PL0T55

Applications

B.S

AIT

ACHING

THE

VTSS

AS AN OUTPUT DEVICE

The subroutine ATTACH assigns logical unit 1 to

the

terminal

number

of

the

VT55.

Then

the

routine

stores

ILUN

= 1

and

IEFN

= 1 in the status table. This subroutine should precede any

other

PLOT55 calls in

a program.

SUBROUTINE ATTACH

COMMON/ST ATUS/IST AT(16)

WRITE(5,l)

1

FORMAT('WHAT

IS

THE

VT55

TERMINAL

NUMBER?')

READ(5,2)

NR

2

FORMAT(02)

CALL ASNLUN(1,'TT',NR)

CALL PLOT55(O,1,l,ISTAT)

RETURN

END

When

you use this routine or any

other

that attaches

the

VT55,

remember

to detach

the

VT55 at the end

of

the program.

CALL PLOT55(O,-1,O,ISTAT)

END

NOTE

ATT ACH will only work with lAS or

RSX-ll

systems.

B-5

APPENDIX C

SUGGESTED BASIC-PLUS APPLICATIONS

Chapter

3 suggested

that

you may want to design some BASIC-PLUS functions

of

your own, using

the

four

functions supplied in your kit (FNV5, FNV6, FNV7,

and

FNV8)

as

building blocks. This appendix gives

you a few samples that show

the

four functions

as

they

might be

combined

to yield

even

higher-level,

and

therefore simpler, graphic support.

Your VT55 software kit

is

supplied

either

on RK05 disk, DECtape, or DOS-II format magnetic tape. Use

the

following procedures to write

the

VT55 software

onto

your RSTS/E system disk:

For RK05 disk distribution:

l.

Place

the

RK05 disk in disk drive 0 (DKO:). Close

the

door.

2.

Log

onto

the system

and

type

the

following

command

in response to

the

READY

message:

MOUNT

DKO:VT55

<CR>

(Change the device

number

to

DKl:

if you are using drive

1.)

3.

Now use

the

PIP

program to copy

the

disk:

READY

PIP

<CR>

=(PIP

VERSION printed by system)

#SY: VT55.BAS=

DKO:

VT55.BAS(200,200)

<CR>

#1Z

READY

DISMOUNT DKO:VT55

<CR>

For DECtape distribution:

The

same

procedure

is

used as for RK05 disks except

that

the

device code,

wherever

it ap-

pears, should be

DTO:

(for DECtape drive 0) or

DTl:

(for drive 1).

The

MOUNT

and

DISMOUNT

commands

may

not

be necessary;

check

with your system manager.

For

magnetic tape distribution:

READY

MOUNT

MTO:

<CR>

READY

C-l

Suggested

BASIC-PL

US Applications

PIP

<CR>

iSY:VT55.BAS=MTO:[200,200]VT55.BAS/OOS

<CR>

#lZ

READY

DISMOUNT

MTO:/UNLOAD

<CR>

All

of

these procedures will write

the

file VT55.BAS

onto

the

system disk

under

the

account that you used

to log on.

C.l

INITIALIZATION

The standard function

FNV7

is

called an initialization function because

it

erases old graphic displays from

the

screen and returns

the

VT55 terminal to its initial state, ready to receive new graphic programming

instructions. What FNV7 does

not

do, however,

is

to also clear

the

screen

of

the

letters and

numbers

that

make up the alphanumeric part

of

a display. In

other

words, FNV7 performs a "single" initialization:

the

graphic display

is

cleared from the screen,

but

the

alphanumeric display remains. FNV7

is

thus useful

when you want to change from one graph to

the

next without changing

the

labels on the axes. In

other

cases you might want to combine

the

graphic initialization

of

FNV7

with a second initialization that clears

the

alphanumeric information from

the

screen

as

well. Consider this example:

15000

DEF

FNV9

15010 D = FNV5(9%,0%,0%) !Cursor to home position.

15020 D = FNV5(10%,0%,0%) !Erase screen.

15030

FNEND

FNV9

is

a different kind

of

single initialization; it clears the alphanumeric display from the screen

but

leaves

the

graphic display alone.

FNV9

could be used by itself in a program you write, or it could be com-

bined with

FNV7

in yet

another

function that performs a "dual" initialization:

15040

DEF

FNV1

15050 D =

FNV7

15060 D =

FNV9

15070

FNEND

If

your graphic programs contained these function definitions,

then

the

statement

D =

FNV7

would clear

only the graphic display, D =

FNV9

would clear only

the

alphanumeric display, and D = FNV1 would

clear both displays.

C.2 GRIDS AND COORDINATE AXES

16000

DEF

FNV2(D1

%,D2%)

16010 D = FNV5(2%,1 %+32%+64%,0%)

16020 FOR

1%

=

1%

TO

512%

16030 D = FNV5(5%,I%-1

%,0%)

C-2

Suggested BASIC-PL

US

Applications

16040

NEXT

1%

16050 FOR

1%

=

1%

TO

236%

16060 D = FNV5(4%,0%,I%-1

%)

16070

NEXT

1%

16080 FOR

1%

=

1%

TO

512%

STEP Dl%

16090 D = FNV5(5%,I%-I%,1

%)

17100

NEXT

1%

17110 FOR

1%

= 1 % TO

236%

STEP

D2%

17120 D = FNV5(4%,1

%,1%-1

%)

17130

NEXT

1%

17140

FNEND

The

statement

D = FNV2(I0%,20%) would display a rectangular grid on

the

VT55 screen, with

the

vertical

grid lines separated by

10

units and

the

horizontal lines separated by 20 units. This particular definition

of

FNV2

is

written in sucp. a way that if

FNV2

is

called several times in the same program, Lines 16020-

16070 will erase

the

old grid before a new one

is

displayed. Grid lines help give a graphic display a visual

scale; for example, when you display a graph on the screen, you may want to know where

the

points x =

0,

x = 25, and x = 50 are located and what

is

the approximate value

of

the graph at these points.

The

markers

described in Chapter 3

will

mark graphs at chosen x positions,

but

that feature will

not

give quite

as

much

numerical information

as

you want.

As

an alternative to actually labeling the screen with numbers, you

could display

the

graph and

then

write the

statement

D = FNV2(25%,5%)

This statement would cover your graph with a "checkerboard," scaling

the

graph in both directions.

The

second line from

the

left would mark

the

position x = 25,

the

third line, x = 50,

and

so forth; in

the

y

direction, you could use

the

horizontal lines, which would be 5 units apart, to estimate

the

value

of

any

point on

the

graph, with an accuracy

of

about 2 units.

You could also use FNV2 to put

just

two important lines, the x and y axes, on the screen, as follows:

D = FNV2(512%,236%)

If

you look back to

the

definition

of

FNV2, you will see that this

statement

would make

FNV2

stop after it

had displayed the first line in each direction, so that you would have a single vertical line at x = 0 (the y

axis) and a single horizontal line at y = 0 (the x axis).

Finally, notice that Line 16010

of

the

FNV2

definition enables both line types

but

does not affect any oth-

er

type

of

graphic figure. Because

FNV2

only affects

the

display

of

grid lines, you could display

one

graph

and

change

the

grid scale

as

many times

as

necessary to get

the

right result.

C-3

Suggested BASIC-PL US Applications

C.3 PLOTTING GRAPHS

Because

the

VT55

is

so often used to display graphs, it

is

usually

convenient

to have a separate function

prepared

that

performs all

the

necessary initialization, enabling, graph

number

selection, and display in

one

step.

The

function FNV3, defined below,

is

suggested for this purpose.

15100

DEF

FNV3(N%)

15110 D = FNV5(7%,0%,0%)

15120 D =

FNV5

(8%,511

%,0%)

15130 D = FNV5(2%,I%+(C7%+1 %)*2%,(C7%+ 1%)*10%)

15140 D = FNV5(3%,-N%,0%)

15150 D =

FNV50%,1

%-C7%,0%)

15160

FNEND

You should take note

of

the

following unusual features

of

this function definition:

l.

Line 15120 draws a vector from

the

origin (0,0) to

the

bottom right

corner

(511,0). This

is

one

of

the

simpler techniques for erasing

the

previous graph for a particular graph

number,

since drawing

such a vector fills up

the

appropriate register

of

the VT55 graphic

memory

with 512 points, all

of

which have a y value

of

O.

2.

Line 15130 uses

the

variable

C7%,

which

is

the

internal variable

that

stores the

current

graph

number

in use

(C7%

=

0%

or 1

%).

You may recall from

the

introduction to Chapter 3

that

you

should avoid using internal variables in your program. In this case, however, the variable

C7%

is

used in the program for

the

same

purpose for which it

is

used internally. You should,

of

course, use

such internal variables with caution, because changing their numerical values would affect

the

sta-

tus

of

the display.

3.

Line 15140

is

simply

the

standard

FNV5

call for creating a graph from

the

array

V5.

In

other

words, you should assign the values you want to graph to

the

array

V5

before writing D =

FNV3

to

create the graph. Line 15140

will

then

plot the first

N%

points from V5, starting with an x position

ofO.

4.

Line 15150 will switch

the

graphic display from

Graph

0 to

Graph

1 and back to

Graph

0 again

automatically as

FNV3

is

called several times in

the

same program.

The

first time

FNV3

is

called

from your program, the graph

will

appear

as

Graph

0;

the

second time, as

Graph

1;

and

so

forth.

If

a very large

number

of

graphs are displayed,

just

remember

that

the

even-numbered

calls will cre-

ate

Graph

1 and

the

odd-numbered

calls will create

Graph

O.

C.4 SHADING A GRAPH

This section suggests

another

function, called

FNV4

here,

that

"shades" a graph, converting it from a nor-

mal graph made up

of

points to a

shaded

graph.

15170

DEFFNV4

15180 D = FNV5(2%,1

%+0

%-C7%)*8%+8%,(l %-C7%)*2%+2%)

15190

FNEND

C-4

Suggested BASIC-PL

US

Applications

FNV

4 uses

the

variable

C7%,

the

graph

number,

in

the

same way as described for

FNVl

FNV

4 should be

called immediately after displaying

the

graph that you want to shade, because

FNV

4 will only shade

the

graph with

the

most recent graph

number,

for example:

15200 V5(I%)=SI

(1%)

FOR

1%=0%

TO

511

%

!SI CONTAINS SINE V ALVES.

15210

D=FNV9

!ERASE SCREEN.

15220 D = FNV3(512%) !PLOT 512-POINT SINE.

15230

D=FNV4

!SHADE

THE

SINE

GRAPH.

15240

V5(I%)=CI0%)

FOR

1%=0%

TO

511

%

!Cl CONTAINS COSINE.

15250 D = FNV3(512%) !PLOT 512-POINT

COSINE.

In this example,

the

sine graph would be shaded, but the cosine graph would remain a standard "point-

plot" graph. Shading

is

very useful in just

such

a case, because the sine and cosine graphs are identical in

shape and can be hard to tell apart unless

one

of

them

is

shaded.

C-5

Alphanumeric array, 2-14

Alphanumeric mode, 1-1,

1-3

APPEND

statement,

3-1

Arrays,

1-3

alphanumeric, 2-14

plotting graphs from,

1-3

ASCII character,

1-1

ASNLUN,2-2

Assigning logical unit numbers, 2-2

Automatic copying, 2-18, 3-12

Automatic graph

number

switching, B-3, C-4

BASIC-PLUS definitions,

3-1

BASIC-PLUS demonstration program, 3-2

BASIC-PLUS programming rules, 3-2

Blank screen, 1-3

Bootstrap, A-I

Channel,

communication, 1-4

Character,

ASCII,

1-1

Characters,

display of, 2-14, 3-13

erasing, 2-13, 2-16, 3-11

CLEAR, 2-13

Clearing graphic memory, 1-2, 2-4, 3-4

Code,

condition,

3-1

Commas in PLOT55, 2-2

trailing, 2-4

Common status table,

B-1

Communication channel, 1-4

Condition code,

3-1

Coordinates,

defining starting, 2-11, 3-9

starting, 1-3

COpy

key, 2-18, 3-13

Copying, 2-18, 3-12

automatic, 2-18, 3-12

Cursor,

1-2

Position, 2-13, 2-16, 3-11

DECpack,

A-I,

C-l

DECtape, A-2,

C-l

Defining starting coordinates, 2-11, 3-9

Definitions,

BASIC-PLUS,

3-1

INDEX

Demonstration program,

BASIC-PLUS, 3-2

Destination point,

1-3

Devices,

storage, A-3

Disabling graphic figures, 1-2, 2-3, 3-4

Display,

suppressing text, 2-18, 3-12

Display-only device,

VT55 as

a,

2-2, 3-3

Displaying text, 2-14, 3-13

Displays,

vertical text, 3-13, B-4

Drawing vectors, 2-11, 3-10

Enabling graphic figures, 1-2, 2-3, 3-4

Erasing graphs, 1-2

Erasing graphs with vectors, 1-4

Erasing text, 2-13, 2-16, 3-11, 3-12

Error return, 3-3

Escape mode, 1-1, 2-16

Escape sequence, 1-1, 2-16, 3-11

Event flags, 1-4, 2-2

Figures,

graphic,

1-2

Figures with same graph

number,

3-15

Flags,

even

t,

1-4, 2-2

FNV5 format, 3-3

Format,

FNV5, 3-3

general PLOT55,

2-1

FOR

TRAN

histograms,

B-3

General PLOT55 format,

2-1

Graph

number,

1-2

figures with same, 3-15

selecting, 2-3, 3-4

Graph

number

switching, automatic, B-3, C-4

Graphic figures, 1-2

disabling, 1-2, 2-3, 3-4

enabling, 1-2, 2-3, 3-4

Graphic memory, 1-2

clearing, 2-4, 3-4

Graphic mode, 1-1, 1-2

Graphing program, sample, 2-6, 3-6

Index-l

Graphs, 1-2, 2-3,

3-1

erasing,

1-2

plotting,

1-2

plotting BASIC-PLUS,

3-5

plotting FORTRAN,

2-5

shaded,

1-2

shading regular,

B-3,

C-4

starting position for, 2-11, 3-9

Graphs from arrays, plotting,

1-3

Graphs with vectors, erasing, 1-4

Hard copy unit, 1-1, 2-17, 2-18, 3-12

Histograms,

3-1

FORTRAN,

B-3

Hold screen command, 2-17, 3-12

Home position,

1-2

Horizontal lines, 1-2, 2-7, 3-7

lAS,

2-2,

2-16, A-2

Initialization,

3-1

ITBL,

2-1,

B-1

Line segments,

1-3

Line-drawing program, sample,

2-8,

3-8

Lines,

horizontal,

1-2

plotting horizontal, 2-7, 3-7

plotting vertical,

2-8,

3-8

vertical,

1-

2,

Listings, 2-18, 3-12

Logical unit number, 1-4,

2-2,

3-3

Logical unit numbers, assigning,

2-2

Magnetic tape, A-2,

C-l

Markers,

1-2

plotting, 2-9,

3-8

sample program for, 2-10,

3-9

Memory;

graphic,

1-2

Messages,

unwanted, 2-3,

3-3

MID function, 3-13

Mode,

alphanumeric, 1-1,

1-3

escape, 1-1, 2-16

graphic, 1-1,

1-2

terminal,

1-1

Name,

task, 2-16

NUL character, 2-14

Number,

graph, 2-3, 3-4

logical unit, 1-4, 2-2, 3-3

terminal, 1-4, 2-2,

3-3

Index

Overlaid program,

2-2

Pause, READ for programmed,

2-7

PAUSE statement, 2-7, 2-16, 2-18

PLOT55,

commas in,

-2-2

PLOT55 format, general,

2-1

Plotting graphs,

1-2

BASIC-PLUS,

3-5

FORTRAN,

2-5

Plotting graphs from arrays,

1-3

Plotting horizontal lines, 2-7, 3-7

Plotting markers, 2-9,

3-8

Plotting single points,

1-

3

Plotting vertical lines, 2-8,

3-8

Point,

destination,

1-3

single, 1-3, 2-11, 3-5, 3-9

Position,

cursor, 2-13, 2-16,

3-11

home,

1-2

Position for graphs, starting, 2-11, 3-9

Program,

overlaid,

2-2

sample for markers, 2-10, 3-9

sample for vectors, 2-12, 3-10

sample graphing, 2-6, 3-6

sample line-drawing, 2-8,

3-8

sample text-display, 2-14, 3-14

Programmed pause, READ for, 2-7

Programming rules, BASIC-PLUS, 3-2

READ for programmed pause,

2-7

Registers, 1-2,

2-3

Regular graphs, shading,

B-3,

C-4

Release screen command, 2-17, 3-12

RESUME, 2-16, 2-18

Return, error, 3-3

RK05, A-I,

C-l

RSTS/E,

1-4

RSX-ll,

1-4, 2-2, 2-16, 2-18, A-2

Rules,

BASIC-PLUS programming, 3-2

Same graph number, figures with, 3-15

Sample graphing program, 2-6, 3-6

Sample line-drawing program, 2-8, 3-8

Sample program for markers, 2-10, 3-9

Sample program for vectors, 2-12, 3-10

Sample text-display program, 2-14, 3-14

Scale, vertical,

B-2,

C-3

Screen, blank

1-3

SCROLL key, 2-18, 3-12

Scrolling, 2-17

Selecting graph number, 1-2, 2-3, 3-4

Index-2

Sequence, escape, 1-1, 2-16,

3-11

Shaded graphs,

1-2

Shading regular graphs,

B-3,

C-4

Single points, 1-3, 2-5, 2-11, 3-5, 3-9

Starting coordinates,

1-

3

defining, 2-11, 3-9

Starting position for graphs, 2-11,

3-9

Status table,

2-1

common,

B-1

use of,

B-1

Storage devices, A-3

Suppressing text display, 2-18, 3-12

Switching terminal modes,

1-3

Table, status, 2-1,

B-1

Task name, 2-16

Terminal mode,

1-1

switching,

1-3

Terminal number, 1-4, 2-2,

3-3

Text,

displaying, 2-14, 3-13

erasing, 2-16, 2-17,

3-11

Text display, suppressing, 2-18, 3-12

Index

Text displays, vertical, 3-13, B-4

Text-display program, sample, 2-14, 3-14

Trailing commas, 2-4

Unwanted messages, 2-3,

3-3

Use

of

status table,

B-1

V5,

3-5

Vector,

zeroing, 1-4,

B-4,

C-4

Vectors,

1-3

drawing, 2-11, 3-10

erasing graphs with, 1-4,

B-4,

C-4

sample program for, 2-12, 3-10

Vertical lines, 1-2, 2-5, 2-8, 3-1, 3-8

Vertical scale,

B-2,

C-3

Vertical text displays, 3-13,

B-4

VT55

as

a display-only device, 2-2,

3-3

VT55.BAS,

3-1

X position, starting, 2-7, 3-9

Zeroing vector, 1-4,

B-4,

C-4

Index-3

READER'S COMMENTS

VT55 Programming Manual

AA-4949A-TC

NOTE: This form

is

for document comments only. DIGITAL will use comments submitted on this form at the

company's discretion. Problems with software should be reported on a Software Performance Report

(SPR) form. If you require a written reply and are eligible to receive one under SPR service, submit

your comments on an SPRform.

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