TM3013501103_MAC_16_LEAP_Assembler_Manual_2ed_Jul1969 TM3013501103 MAC 16 LEAP Assembler Manual 2ed Jul1969

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July 1969 Second Edition

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TABLE OF CONTENTS
SECTION 1 - INTRODUCTION

1-1

GENERAL

1-1

Programmer Options

1-1

Features

1-1

THE ASSEMBLY PROCESS

1-2

Pass 1

1-2

Pass 2

1-2

SECTION 2 - LEAP LANGUAGE SYNTAX

2-1

GENERAL

2-1

THE CHARACTER SET

2-1

FIELDS

2-1

The LOCATION Field

2-2

Symbols

2-2

The OPERATION Field

2-2

LEAP CODING FORM

2-3

The VARIABLE Field

2-4

The COMMENTS Field

2-4
2-4
2-4
2-4
2-4
2-5
2-5
2-5
2-5
2-5
2-5
2-6
2-6
2-6
2-7
2-8
2-8
2-8
2-8
2-8
2-9
2-9
2-9
2-9
2-9
2-9

The IDENTIFICATION Field
EXPRESSIONS
Elements
Value Assignment
Mode Assignment
Absolute
External
Relocatable
Data
Single Precision, Fixed-Point
Double Precision, Fixed-Point
Single Precision, Floating-Point
Double Precision, Floating-Point
LEAP CODING FORM
Examples of Decimal Data
Hexadecimal
USASCII
The Asterisk as an Element
Expression Operators
Elements and Operators in Expressions
Absolute Values
Relocatable Values
External Values
The Asterisk
Uses of Parentheses in Expressions
Summary of Legal and Illegal Expressions

2-10

iii

TABLE OF CONTENTS (cont'd)
LITERALS

2-10

SUMMARY OF ASTERISK USES

2-10

ERROR CODES

2-11

SECTION 3 - LEAP PSEUDO-OPERATIONS
ASSEMBLY CONTROLLING PSEUDO-OPERATIONS

3-1

BOOT - BOOTSTRAP FORMAT

3-1

DUP-Duplicate the Next Source Line

3-2

END - End of Source Program

3-2

ORG - Set Program Origin

3-3

SKIPF - Skip if False

3-3

CODING FORM

3-3

SKIPT - Skip if True

3-4

SKIPT ARG, 2*ARG

3-4

SKIPF ARG-3,9
CODING FORM

3-4
3-4

LDI (3-ARG)*2

3-5

TWA

3-5

STACOUNT

3-5

LDX = Al05

3-5

CLA

3-5

LOOP STA 0,1

3-5

DNX 1

3-5

INC COUNT

3-5

JMP LOOP

3-5

DATA GENERATING PSEUDO-OPERATIONS

3-5

DC - Data Constant

3-5

MAC 16 Print Out Example

3-6

CODING FORM

3-7

PTR - Address Pointer
LISTING CONTROLLING PSEUDO-OPERATIONS

3-8
3-8
3-8

EJECT - Skip to the Top of the Next Page

3-8

LIST - List During Pass 2

3-8

NLiST - Don't List During Pass 2

3-9

SPACE - Space n Lines Before Resuming Listing

3-9

TITLE - heading to be Printed at Top of Page

3-9

TXT - CHARACTER String

LSTSY - List Symbol Table

3-1

3-9

EXTERNAL REFERENCE PSEUDO-OPERATIONS

3-10

EXTRN - External Symbol

3-10

ENTRY - External Symbol Definition

3-10

STORAGE ALLOCATING PSEUDO-OPERATIONS

3-11

CLEAR - Clear and Reserve an Area

3-11

COMN - Reserve an Area in COMMON

3-12

DS - Reserve Data Storage Area

3-12

TABLE OF CONTENTS (cont'd)
SYMBOL DEFINING PSEUDO-OPERATIONS

3-13

EOU - Symbol Equals Value and Type of Expression

3-13

EOUR - Symbol Equals Value of Expression, Relocatable Mode

3-14

REDEF - Redefine Symbol

3-14

MISCELLANEOUS PSEUDO-OPERATIONS
SETB - Set the Loading B Flip-Flop

3-14
3-14

RESB - Reset the Loading B Flip-Flop

3-14

PRINT - PRINT During Pass 1

3-15

MACRO Definition'

3-15

Parameters

3-15

EXAMPLE 1 CODING FORM

3-16

EXAMPLE 2 CODING FORM

3-17

EXAMPLE 3 CODING FORM

3-18

SECTION 4 - ASSEMBLING MAC 16 INSTRUCTIONS

4-1

CLASS 0: 16 BIT, UNMODIFIED

4-1

CLASS 1: MEMORY REFERENCE

4-1

CLASS 2: I/O INSTRUCTIONS

4-1

CLASS 3: SKIP INSTRUCTIONS

4-2

CLASS 4: N FI ELD

4-2

CLASS 5: IMMEDIATES

4-2

CLASS 6: STATUS MODIFIERS

4-2

SECTION 5 -INPUT/OUTPUT

5-1

SOURCE PROGRAM PREPARATION

5-1

Preamble-Start-of-File

5-1

Card I mages

5-1

End-of-File

5-1

ASSEMBLY LISTING FORMAT

5-1

Page Format

5-1

Line Format

5-1

Value Formats (Positions 13-21)

5-2

OBJECT CODE

5-3

Bootstrap Format

5-3

Extended Format

5-3

Checksum

5-5

APPENDIX A - USASCII CHARACTER SET AND HEXADECIMAL CODES

A-1

APPENDIX B - MAC 16 MACHINE OPERATIONS

B-1

APPENDIX C - LEAP PSEUDO-OPERATIONS

C-1

Section 1

I ntrod uction

This manual contains a discussion of the Lockheed

of assembly are (1) absolute and (2) relocatable. Through

Electronics Assembly Program (LEAP) for the MAC 16

the use of pseudo-operations the programmer can change a

computer. Included are discussions of LEAP and its pur-

mode at will. For example, to access the MAC 16 executive

pose, the LEAP language and the rules for using the

page in memory, an absolute memory location is specified;

language, programming examples using the LEAP language,

whereas, unless the program is assembled in bootstrap

and instructions for preparing a program for assembly.

format, the majority of memory reference instructions refer

Assumption is made that the reader is familiar with the

to locations that are of relocatable mode.

MAC 16 (described in the MAC 16 Programmer's Manual)

The two object code formats are (1) bootstrap and (2)

and is generally familiar with computer programming at the

extended. A program object code format cannot be

assembly language level.

changed during assembly. Basically, what makes assembling

GENERAL

format is that in bootstrap format the programmer must do

in bootstrap format different from assembling in extended
his own memory reference depaging, and also, he cannot
An assembly program is a language translator that trans-

use external references or use the relocation mode of

lates one language (called the source language) into another
language (called the object language). The process by which

extended format, depaging is automatic during the loading

assembly.

See Section

3 for an explanation. Under

the translation takes place is called the assembly process.

process, and also, both external and relocatable references

The source language is in symbolic form, a form easily

are allowed.

understood (and used) by the programmer. The object
language is in numeric form, a form understood by the

Features

computer.
As in all languages, the LEAP source language has gram-

Some LEAP features follow:

matical rules that must be followed so that the "sender"

1. Two-pass assembler

(the programmer) can be understood by the "receiver" (the

2. The programmer completely controls depaging. I f the
programmer wishes, the assembler/loader automatically

LEAP program). The entire set of grammatical rules of
language is called the syntax of the language. I n later sec-

depages programs of any size

tions, the LEAP syntax is covered in detail; this section is

3. As many as 200 symbols and/or literals can be defined

concerned primarily with general descriptive information

within the symbol table of the assembler operating on a

and definitions of terms.

basic 4K MAC 16
4. Pseudo-operations are provided for:

Programmer Options

The LEAP assembly language provides several basic

defining constants of various types
1. Single and double precision, fixed-point (with
scaling)

programmer options that a user may exercise. First the

2. Single and double precision, floating-point

LEAP language contains two assembly modes, and second,
two formats for object code generation. The two modes

3. Hexadecimal
4. Text

1-1

b. conditional assembling

symbol table with the value of the VARIABLE field and

LEAP reads the next source line. Each time a pseudo-

defining COMMON data storage

d. reserving and/or clearing areas of computer memory

operation that modifies one of the Location Counters is

defining external programs and data

encountered, the proper Location Counter is modified

controlling the format of the object code (extended

according to what appears in the VARIABLE field. If a

or bootstrap)

symbol appears in the LOCA TI ON field of one of these

g. controlling the program listing
5. Expressions are allowed, including parenthetical subexpressions, with a full range of operators

pseudo-operations, a value may be assigned before or after
the modification, depending on the pseudo-operation. All
MAC 16 instructions cause the LEAP Location Counter to

6. Literals are allowed

be increased by one. If a symbol is encountered in the

LOCATION field of a MAC 16 instruction, it is assigned the

16 error flags (up to 4 printed with each source line)

8. Macros

value of the Location Counter before the increase. If a

9. Symbol-table dump (in alphabetical order).

macro definition is encountered, the macro is stored for a
macro call. When a call is encountered for the macro, it is

THE ASSEMBLY PROCESS

inserted in the program in place of its call. This process
continues until the end of the program (END pseudo-

LEAP reads the source language (one line or statement
at a time) and produces the object language. The Loader
reads the object language, does whatever processing is

operation) is encountered. Pass 2 now starts.

Pass 2

necessary (depaging, relocating, etc.), and stores the object
program in memory.

LEAP starts reading the source program again. If the

To assemble a program, LEAP reads the source program

operation is a pseudo-operation controlling the assembly

two times. Each reading is called a pass; thus, LEAP is a

process, the proper function is performed. If the operation

two-paSs assembler. Object code is produced during pass 2.

is a MAC 16 machine instruction, the proper operation

Pass 1

evaluated in the VARIABLE field and its value is inserted

The purpose of pass 1 is to:

VARIABLE field). The second subfield is evaluated and if

1. Develop a table of defined symbols and assign memory

not zero, the index bit is set to one in the object code (if it

code is inserted into the object code. The first subfield is
into the object code (if it is legal to have a value in the

addresses (values) to them
2. Develop a table of external references
3. Develop a table of literals and assign values to them
4.. Define Macros.

is legal to have indexing for this instruction). If the first
subfield of the VARIABLE field was preceded by an
asterisk, the indirect address bit is set to one in the object
code (if indirect addressing is legal for this instruction). The
source line and the object code is now transferred to the

At the start of pass 1, the two location counters used

program listing device. The object code is placed in a table

by LEAP are set to zero (Execution Location Counter, and

and when the table is full, the code is transferred to the

Common Counter); a source line is then read. If the source

object producing device.

line is a comment, the source line is passed over and LEAP

1-2

This process continues until the end of the source

reads the next source line. If the OPERATION field con-

program

tains a symbol-defining pseudo-operation, the symbol

encountered. The assembler then produces the object code

(END

pseudo-operation)

is once

again

appearing in the LOCATION field is entered into the

for literals and the process is complete.

Section 2

LEAP
Language
Syntax

This section contains the grammatical rules (syntax) of

by one or more blanks. The LOCATION field begins with

the LEAP language. Rules for forming symbols, expres-

the first character of the statement, and is terminated by

sions, data, operations, etc. are discussed along with some

the first blank. The OPERATION field immediately follows

possible error conditions and resultant consequences. This

the LOCATION field and is terminated with a blank. The

section, along with Sections 3 and 4 provides a complete

VARIABLE (operand) field is defined by the first non-

description of the entire LEAP language. This Section is

blank character following the OPERATION field if this

primarily concerned with statement format; Sections 3 and

character is within 5 blank characters of the OPERATION

descriptions of the pseudo-operations and

field, and is terminated by the first blank character or by an

4 contain

machine operations recognized by LEAP.

end of record signal. (The end of record signal on paper
tape is defined as a carriage return-line. feed.) If the first

GENERAL

non-blank character after the OPERATION field is greater
than 5 blank characters away, or if there is a non-blank

Throughout this manual, little reference is made to
input/output media. LEAP is not concerned with external
representation of the source input, or the object and listing

character following the VARIABLE field, the COMMENTS
field is defined. The COMMENTS field is terminated either
by the end-of-record signal or by the eightieth character.

output but communicates with the outside world via an

An entire line of comments can be entered by writing an

elementary executive. (LEAP asks for a source line and is

asterisk in the first character position of the line. Fields are

not concerned with where the executive received the source

usually written in fixed positions on a coding sheet; how-

line; in the same manner, the object code and listing code

ever, any format that satisfies the above definition is per-

are given to the executive for processing.)

missible. Free form tolerance is of greatest advantage in

The internal format for the source, object, and listing are:
SOURCE-SO-column card image
OBJECT-72-column binary card image
LISTING-lOS-column print image, plus
carriage control characters
An example of the coding sheet is shown on page 2-3.
Statements are composed of fields; each containing a
constant, a symbol, an expression, or two or more of these
separated by commas. The assembler evaluates constants
and expressions, and saves a table of the symbols and the
values assigned to these symbols when the programmer (or

overcoming a common keypunching error; that is, starting a
field in the wrong column or character position of the line.
THE CHARACTER SET
The character set used by LEAP (and the MAC 16) is
the USA Standard Code for I nformation Interchange
(USASCII) set. There is syntactic significance to some of
the characters, but this is discussed later (see ELEMENTS
later in this section). The USASCII character set is listed in
APPENDIX A.

FIELDS

the assembly program itself) defines them.
The four fields composing a statement are: the LOCA-

The LEAP COOl NG FORM is used to assist the pro-

TION field, the OPERATION field, the VARIABLE field,

grammer in writing a program in a consistent format

and the COMMENT field, in that order. Fields are separated

acceptable to LEAP. Each line of the form is used for

2-1

writing one symbolic line of the program (called a source

3P14 Does not begin with an alphabetic character

statement). The source statement is divided into five fields:
LOCATION
OPERATION

AB.CD Illegal character used (.)
ALPHABET More than six characters
, 1F F Illegal character used (')

VARIABLE

:AB doesn't begin with an alphabetic character

COMMENTS
IDENTIFICATION
No provisions in LEAP are made for continuation of

If an asterisk (*) appears in card column 1 (and only in
card column 1) of the LOCA TI ON field, the entire source

source statements except as outlined in macro definition

line is treated as a comment. That is, it will be printed on

(Section 3).

the listing, but otherwise ignored by the assembler. This
allows the programmer to freely document his program list-

The LOCATION Field

ing without adding to the size of his object code.
The following are the only entries allowed in the

The LOCATION field normally is used for a symbol by

LOCATION field:

which a source statement can be referenced from other

all blank

parts of the source program (often referred to as the

legal symbol

symbolic location). The LOCATION field has a special

*in column 1

meaning for some pseudo-operations and is ignored by
others; the discussion with each pseudo-operation (Section
3) specifically states the use of the LOCATION field.

Violation of this rule causes the error code "S" to be
printed on the listing.

A legal symbol within the LOCATION field consists of

The remaining discussion assumes that no asterisk is

one or more (up to a maximum of six) alphanumeric char-

written in card column 1 (the remainder of the card is

acters (A through Z, 0 thru 9, and colon (:)), the first of

ignored, if a comment).

which must be alphabetic. The symbol must start in the
first character pOSition of the LOCA TI ON field and is

The OPERATION Field

terminated by the first blank.
The special character colon (:) is considered a numeric

The OPERATION field is used for entering the

symbol by the syntax of the LEAP assembler when used

mnemonic for a desired operation. This operation can be

within the LOCATION or VARIABLE fields.

the mnemonic for a pseudo-operation (see Section 3) or a
machine operation (see Section 4). When the mnemonic

Symbols

represents one of the MAC 16 machine operations, LEAP
inserts the appropriate code for that operation into the

Symbols consist of alphabetic characters, (letters A
through Z), numeric characters (numbers 0 through 9 and

mnemonic represents one of the LEAP pseudo-operations,

colon (:)) or a combination of alphabetic and numeric characters. A symbol may be formed of one to six characters,

the instructed action is taken. Appendices Band C sum-

but the first character of every symbol must be alphabetic.

OPERATION field. The contents of the OPERATION field

The special character colon (:) is considered a numeric
character by the syntax of LEAP.
Example:
LEGAL
ALPHA

marize the mnemonics that are accepted by LEAP in the
are optional i.e., a macro (see Section 3). The OPERATION
field starts with the first non-blank character following the
LOCATION field and is terminated by the first blank character encountered.
A mnemonic entry within the OPERATION field con-

sists of one to six alphanumeric characters (A thru Z, 0 thru

A239B

9, and colon (:)), the first of which must be alphabetic.

P68475

2-2

object code produced by the source statement. When the

The remaining characters must conform to the syntax

for either a mnemonic or a valid pseudo-operation, a

ZAP:U

machine operation or a predefined macro. Otherwise, the
statement is flagged with an error code "0".

I LLEGAL (Error Code "S")

I ) . LEAP CODING FORM
PROGRAMMER

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LOCKHEED ELECTRONICS COMPANY DATA PRODUCTS DIVISION

The VARIABLE Field

sion of the COMMENTS field. Otherwise, IDENTIFICATION is treated in the same manner as described for COM-

The VARI ABLE field or operand is so called because of

MENTS.

its function as modifier to the operation. The VARIABLE
field starts with the first non-blank character following the
OPERATION field and is terminated with the first blank
encountered (or column 80, whichever is first). It is most
commonly used for specifying the variable part of a
machine instruction (address, M, N, amount of shift, etc.),
and the index register flag. When used for these purposes,
the

VARIABLE

field is actyally broken down into

subfields.
For memory-reference instructions, there are two subfields: the address subfield and the X (index) subfield. The
programmer indicates the separation of these two subfields
by placing a comma (,) between them.
Section 3 includes a description for the use of the
VARIABLE field on various pseudo-operations; Section 4
describes the uses for the various machine operations.
If an asterisk (*) preceeds the mnemonic in the VARIABLE field, it is interpreted to mean that the instruction
indirect address tag, I, is to be set to a one. This is allowed
with all memory reference operations. If the operation is

EXPRESSIONS

It is often desirable to specify a value in the VARIABLE field that is generated by combining more than one
value. LEAP provides the programmer with this capability
by allowing expressions in the VARIABLE field. An expression is composed of elements and operators; it can be composed of a single element, or n elements separated by n-1
operators. The length of an expression is limited only to the
size of the VARIABLE field.
If two or more elements appear in an expression, all of
the elements in the expression must be single precision; i.e.,
a value that is not larger than 16 bits. The only time an
element is multiple precision (e.g., double precision numbers, or text string of more than two characters, etc.) is
when the element is in the VARIABLE field of a multiple
precision DC or TXT pseudo-operation. Illegal use of
multiple precision elements causes the error code "C" to be
printed on the listing.

not a memory reference type, the error code "I" is printed
on the listing.
LEAP terminates the scan of the VARIABLE field
when the first blank is encountered (exceptions: USASCII
data and the TXT and TITLE pseudo-operations).
The COMMENTS Field

The COMMENTS field is used for any remarks that the
programmer cares to write. The contents of the COMMENTS field are printed on the program listing, but are
otherwise ignored by the assembler.
The COMMENTS field starts with the first blank
following the VARIABLE FIELD (except as noted above).
Although the starting position of the COMMENTS field is

Elements

An element is an operand in an expression. An element
may be a symbol, a datum, or the asterisk.
As stated, LEAP places special syntactic significance on
some characters in the character set. Some of this significance is associated with the first character of an element.
If the first character of an element is:
A thru Z: the element is a symbol

a thru

9 or the decimal point: the element is a decimal

number

$: the element is a hexadecimal number
': the element is USASCII data.

variable, the program listing is less confusing if the programmer always starts a comment in the same column. By

Value Assignment

following this rule, a predictable separation exists between
the program instructions and the commentary, thus,
making a more readable listing.

A symbol normally has an assigned value when the
symbol is encountered in the LOCATION field of a source
line. When an undefined symbol (not in the LOCATION

The IDENTIFICATION Field

field of any source line) is encountered in the VARI ABLE
field, LEAP assigns a value of zero and causes the error

The IDENTIFICATION field may be used for record
2-4

identification (if cards are used) and is cQnsidered an exten-

code "U" to be printed with the line in which the symbol
was encountered.

If a symbol does not have a unique value (i.e., it was
encountered in the LOCA TI ON field of more than one
source line), it is considered to be a multiple definition. The
value of the symbol is the value assigned by LEAP the last
time the symbol was encountered in the LOCATION field;
subsequent encounters change the value. Multiple definitions cause the error code "0" to be printed with the line
in which the symbol is encountered in the LOCATION
field. If a source statement refers to the multiply defined
symbol in the VARIABLE field, the error code "M" is

3. The symbol appears in the LOCATION field of a
COMN pseudo-operation.
Data
LEAP will process three different data notations as elements: decimal, hexadecimal, and USASCII text.
DECIMAL
Single Precision, Fixed-Point (4.5 decimal digits)

printed with the line in which the symbol is encountered.

SINGLE PRECISION, FIXED-POINT (1 word)

The value of a symbol encountered in a pseudooperation LOCA TI ON field is the value and type of the

LEAP LOCATION counter at the time the source line is

encountered with two exceptions. These exceptions are the

15 bits of data
15

A single precision, fixed-point decimal number requires

EQU and EQUR pseudo-operations (see Section 3 for

one computer word (sign and 15 bits) and is written in two

further explanation.)

parts: the numeric part and the scaling part.

Mode Assignment

The numeric part of the single precision, fixed-point
number is a signed or unsigned decimal number, with or

The mode of a symbol is dependent on the mode of the

without a decimal point. If no sign is specified, the number

value assigned to the symbol. A value may be either abso-

is assumed to be positive. If no decimal point is specified, it

lute, external, or relocatable.

is assumed to be immediately to the right of the final digit
of the numeric part (a decimal integer).

Absolute

The scaling part of the single precision, fixed-point
number is composed of the binary scale factor and the

A symbol is absolute if the value assigned to the symbol
is absolute. This can be done in two ways:
1. LEAP assigns the value of the LOCA TI ON counter and
the mode of assembly is absolute; or,
2. the value is assigned through the use of a symboldefining pseudo-operation and the expression in the
VARIABLE field is absolute.
External

decimal scale factor. The binary scale factor may be
omitted if no decimal point is included and must be
included when the binary scale factor is the letter B
followed by a signed or unsigned decimal integer. The
binary scale factor specifies the position of the understood
binary point relative to the machine binary point (between
bit positions 0 and] of the computer word). If the binary
scale factor is positive, the understood binary point is to
the right of the machine binary point, if negative, it is to
the left of the machine binary point.

A symbol is external if it appears in the VARIABLE
field of an EXTRN pseudo- operation.

The decimal scale factor may be omitted, but if
included, it is the letter E followed by a signed or unsigned
decimal integer. The decimal scale factor specifies the loca-

Relocatable

tion of the decimal point in the numeric part relative to the
written decimal point (if no decimal point had been

A symbol is relocatable if the value assigned to the
symbol is relocatable.
This can be done in three ways:
1. LEAP assigns the value of the LOCATION counter and

written, it is assumed to be immediately to the right of the
final digit). If the decimal scale factor is positive, the
decimal point is to the right; if negative, the decimal point
is to the left.

the mode of assembly is relocatable; or,
2. the value is assigned through the use of a symbol-

The binary scale factor may appear before the decimal

defining pseudo-operation and the expression in the

scale factor, or vice versa, but the scale factors must appear

VARIABLE field is relocatable; or

after the numeric part (error code "C", if not).

2-5

If information is lost in the most significant part of the
word during conversion (improper scaling), the error code
"C" is printed on the listing.

hexadecimal digits of data) and is written in two parts: the
numeric part and the scaling part.
The numeric part of the single precision, floating-point
number is a signed or unsigned decimal number, with a

Double Precision. Fixed-Point (9.4 decimal digits)

decimal point. If no sign is specified, the number is assumed
to be positive. If no decimal point is specified, the number

DOUBLE PRECISION, FIXED-POINT (2 words)

is assumed to be an integer.
The scaling part of the single precision, floating-point

word

IS I

number is the decimal scale factor. The decimal scale factor
specifies the location of the decimal point relative to the

15 most-significant bits

written decimal point in the numeric part. If the decimal

scale factor is positive, the decimal point is to the right; if

(see footnote 1.)

negative, the decimal point is to the left.
word 2

Double Precision. Floating-Point (16.7 significant decimal

15-bit extension

digits)

*Unused

word
S

double

precision,

fixed-point

decimal

number

requires two computer words (sign and 31 bits). A double
precision, fixed-point number is written the same way as
the single precision number, except that two B's are written

EXP fraction

8
15
(2 hexadecimal digits
of fraction)

word 2

for the binary scale factor or two E's are written for the
decimal scale factor (or both).

Single Precision. Floating-Point (7 significant decimal
digits)

word 3

SINGLE PRECISION, FLOATING-POINT (2 words)

15
(4 hexadecimal extension)

word
word 4

EXP

7
8
15
(see footnotes 2 and 3) (2 hexadecimal

15
(4 hexadecimal extension)

digits of Fraction)
A double precision, floating-point decimal number
word 2

requires four computer words (sign, 7-bit hexadecimal
exponent, 14 hexadecimal digits of data).

(4 hexidecimal extension)

A double precision, floating-point number is written the
same way as the single precision number, except that a

single

precision, floating-point decimal number

requires two computer words (sign, 7-bit exponent, and 6

decimal scale factor must be specified, and two E's must be
written for the decimal scale factor.

Notes:

2-6

S is the sign

EXP is the 7-bit exponent (power of 16), offset by 4016' The decimal range of the hexadecimal exponent is +63 to -64 (approximately

10+19 to 10_19).
Fraction is the normalized hexadecimal fraction; extensions are 4 hexadecimal digits.

t).

LEAP CODING FORM

PROGRAMMER

DATE

PROGRAM
LOCATION
1234~6

IT~

CHARGE
OPERATION
7 8 9 10 11 12 13 14 15

E~ A~ PL r;

I GI1

E~ l~ PI- ~ ~

14 Glt

IE~ fA III PIL te ~

10
11
12
13

~GI~

IEiYII NP

ttlA ~~

lor,.

I~ 14

ID~

VARIABLE
20

1':111 I II

PAGE

132

u~ TI~ AT IE '~ rtl~ Ie

ITT Ill! N Q!!F

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Ie ~I' IAL S "IE ~ C1 10 !~O 010
-~

Is: itot INA L ~A h"~

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IDENTI F ICATION

COMMENTS

I" E~

lUI

~b II

~~ ~~

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25

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28
29

30
LECW FORM 213-1

r:->

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LOCKHEED ELECTRONICS COMPANY DATA PRODUCTS DIVISION

Examples of Decimal Data

NUMBER

FORMAT

Expression Operators
AS IT APPEARS ON
THE LISTING
(HEXADECIMAL)

I tems are combined using the operators defined in the
table below. The table also is a list of hierarchy numbers for
determining how the value of an expression is computed.

1.
1.B15
.lEE1B31

single precision, fixed-point

0001

sin~le

4110

before operations having lesser hierarchical value. Opera-

0000

tions with the same hierarchical value are performed from

precision, floating-point

single precision, fixed-point
double precision, fixed-point

0001

left to right. (Parentheses may be used to change this

0000

hierarchical structure.)

0001
-1.
1.EE-l

Operations with greater hierarchical value are performed

single precision, floating-point

Cll0
0000

double precision, floating-point

4019
9999
9999
9999

Table 3
Hierarchy

Operator

Description

Logical binary left shift

Arithmetic product

Arithmetic quotient

Arithmetic sum

Hexadecimal
A hexadecimal number is represented by the dollar sign
($) followed by a signed or unsigned string of hexadecimal

digits. A single precision hexadecimal number has less than
five digits; a double precision hexadecimal number has
more than four digits, but fewer than nine digits. If a
negative sign is specified, the resulting number is two's
complement.
USASCII

USASCII text is defined to be the single quote (')

4
3

terminates the strings.

Boolean less than
Boolean equals

Boolean greater than

Logical product (AND)

Logical sum (OR)

followed by a string of characters. Two characters are
stored per word. If more than two characters are written,
the string will use more than one word. A single quote (')

Arithmetic difference

Control characters (carriage return, line feed, tab, etc.)
and the single quote (') are not allowed in a USASCII text

Logical difference

string. If it is necessary to specify any of these a separate

(exclusive OR)

DC statement must be used, with the character(s) specified
in hexadecimal.
Example of USASCII characters in a DC statement:
DC,4 'WEDNESDA'

The Asterisk As An Element

2-8

An expression can have a leading minus sign; if so, its
value is computed as though a zero preceded the minus
sign. Thu~ - 1;30;6 (-2) is evaluated as 0-(13%(-2)), which is
not the same as (0-13% (-2).

A single asterisk (*) may be used as an element in an

The value of an item will be right-justified in its

expression. The value of the asterisk is the value of the

generated resultant field and unspecified leading bit posi-

LOCATION counter at the time the asterisk is encountered

tions will contain zeros.

during the expression evaluation. The value mode of the

Note that the subexpression item provides for paren-

asterisk depends on the current mode of assembly (absolute

thetical expressions; i.e., according to the above rules

or relocatable).

(A+B)/2 is a valid expression.

Elements And Operators In Expressions
If two or more elements appear in an expression, all of
the value are treated as 16-bit values. A multiple precision
element must exist alone in an expression and can only be
used in the VARIABLE field of a DC or TXT pseudooperation.
Two consecutive elements are not permitted without an
operator separating them (3M does not mean 3*M and will
cause the error code "E" to be printed on the listing).
Consecutive operators are not permitted without elements except for the minus sign (-). Any of the elements
described in this section may be used in expressions (with
the above-noted restriction on multiple precision elements).
Certain combinations, described below, have no meaning
and are not permitted. The table at the end of this section
summarizes the legal and illegal combinations.

Absolute Values
Any 16-bit absolute value can be combined with any
other 16-bit absolute value with any operator. Absolute
values are:
Symbols with absolute values
Data Elements

Relocatable Values
Only one relocatable value can exist in an expression,
unless the combination of relocatable values causes an
absolute result. For example, a relocatable value subtracted
from a relocatable value produces an absolute result. It is
the programmer's responsibility to group the elements in an
expression so that the value of the entire expression is
dependent on only one relocatable element. Violation of
this rule causes the error code "R" to be printed on the
listing.

External Values
External values cannot be combined with other
expressions elements. Violation of this rule causes the error
code "R" to be printed on the listing.
Relocatable and external values are not defined until
load time; absolute values are known at assembly time. The
use of relocatable and external values is assumed to be
associated with a reference to a memory location by the
Extended Loader. The following are the only memoryreference values recognized by the Extended Loader.

ABSOLUTE VALUE . Depage
POSTITIVE RELOCATABLE
VALUE.

. Add relocation constant to
value and depage
POSITIVE EXTERNAL

VALU E.

• .

Add value to value of external
symbol and depage.

The Asterisk
If the asterisk is used as an element and it has a reiDeatable value, the restrictions described above apply for
relocatable values in expressions. There is no restriction
regarding the use of an asterisk as an absolute value.
The asterisk is also an operator and there is one
syntactical ambiguity in the use of the asterisk for either
purpose. LEAP evaluates asterisks in the VARI ABLE field
"in the following manner. The first element, if an asterisk,
forces LEAP to evaluate the second element. If the second
item is a legal operator (+.-,*.1, etc., the value of the first
item (*) will be the value and type of the LOCATION
counter. If the second item is a legal element the first item
(*) will be used to define an indirect call to a location. With
this in mind the following example will be easy to decipher.
Example:
LOA **2
The value of the expression is the value of the
LOCATION counter multiplied by two. If the programmer
wished the value to be indirect through LOCATION
counter +2, a name (label) should be assigned to the desired
location and the coding written as
LOA *NAME

Uses of Parentheses In Expressions
LEAP gives the programmer the capability to specify
subexpressions within expressions. A subexpression is a
string of elements and operators bounded by parentheses. A
subexpression starts after a left parenthesis and is closed
when a matching right parenthesis is encountered. After
evaluating a subexpression, the resulting 16-bit value is
treated as an element by LEAP.
Parenthetical subexpressions may be nested within subexpressions. LEAP can evaluate up to five levels of nested
parenthetical subexpressions. However, for each left parenthesis encountered, there must be a matching right
parenthesis within the expression. If there are more left or
right parentheses than the other, the error code liZ" is
printed on the listing.

2-9

Examples:

The value and mode of a literal is assigned at the end of

(((((A+B)*(C-D))/E) & F)

the first pass over the source program. For each literal

$FFFF)+l

encountered in the literal table, LEAP assigns the value of
(A)+(B)-(C*D)

the LOCATION counter and then increases the LOCATION

Note, that redundant parentheses are allowed; A+B-C*D
would produce exactly the same results as this example.

counter by one. Mode assignment is dependent on the
mode of assembly at the time the EN D pseudo-operation is
encountered. If LEAP is assembling in the absolute mode,

ALPHA/(BETA-GAMMA-DEL TA)

the literals will be the absolute mode; if in the relocatable

(BITS/2) & 1

mode, the mode will be relocatable.

Shifts BITS right 1 place and keeps only low-order bit.

Examples:
=' AB'

-EXTENT

requires one word (USASCII string, two characters
per word).

Forms two's complement

=$lFF

Summary of Legal and Illegal Expressions

requires one word (single precision, hexadecimal).

When LEAP is assembling in bootstrap format, literals are
used only if the program, including all literals, is less than

The following table lists the legal and illegal combinations of elements in expressions. If an illegal combination is

one page in size.
A literal expression is composed of more than one ele-

encountered, the error code "R" will be printed on the

ment (or a single element with a 16-bit value), and is always

listing. The table is applicable to values and intermediate

a 16-bit word containing the value of the expression. Thus,

values. For example, the table shows that r+r is illegal;

absolute, external, or relocatable values are elements in

therefore, r+r-r would also be illegal; however, r+(r-r) would

literals.

be interpreted as r+a, which is legal.

Examples:
LDA

LEGAL

=*+3

means "load the A-register with a word
containing the value of *+3." It does not

a=a

r=r

a+a=a

a+r=r

a-a=a

r+a=r

a*a=a

r-a=r

a/a=a
a&a=a
a@a=a

r-r=a

mean "load the A-register with the word

e=e

that is three locations away."
EXTRN SINE
LDX

=SINE

means "load the index register with the
external value of SINE." At execution
time, this value will be the memory

a!a=a

address of where SI N E had been placed

a = absolute; e=external; r=relocatable

by the loader.

I LLEGAL (error code "R")

SUMMARY OF ASTERISK USES

Any other combination of elements is illegal.
No ~ or I item may be an element of: * .I,&,@,! operators

The following are the various uses of the asterisk and
their meanings:

LITERALS

1. An asterisk in column 1 of the source statement: treat
entire source line as a comment.

A literal is the equals sign(=), followed by any legal
expression. Multiple precision elements are not permitted
following the equals sign. If a multiple precision element is
encountered, the error code "E" is printed on the listing.
The value of a literal is the 16-bit address of the
2-10

memory location in which the literal is stored.

2. An asterisk preceding a VARIABLE field mnemonic:
set indirect address flag.
3. An asterisk as an element in an expression: current
value and mode of the LOCATION counter.
4. An asterisk as an operator: form the product of the
adjacent elements.

ERROR CODES

OPERATION CODE
An illegal mnemonic, or undefined mnemonic has been
encountered in the OPERATION field.

The following is a summary of the error codes and their
P

meanings:
A

ADDRESS SUBFIELD

PHASE
A relocatable expression is not permitted, or an expression has an element that has not been previously

A null expression was encountered in the address sub-

defined.

field (memory reference instructions only). There must
always be an entry in the address subfield of memory
reference instructions, even if it is just
B

a (zero).

combination of relocatable and/or external elements.

BOOTSTRAP
While running the bootstrap format, either a memory

reference instruction has attempted to address a loca-

RELOCATABLE
An expression has been encountered with an illegal

SYMBOL
An illegal character has been encountered in the LOCA-

tion not in the current page or the base page, or an

TION field; or a symbol-definition has been attempted

illegal pseudo-operation has been encountered.

without starting the symbol with an alphabetic char-

CONVERSION

acter; or a symbol has been encountered in the VARI-

A data element cannot be correctly converted. This is

ABLE field with too many characters (more than six);

usually associated with an illegal character or combina-

or a symbol has been omitted in the LOCA TI ON field

tion or characters in a data element; however, too many

for a pseudo-operation requiring a symbol.

characters in a hexadecimal element or improper scaling
of a decimal element can also cause this error.
D

U UNDEFINED
A reference has been made to a symbol that is not

DOUBLE DEFINITION

defined anywhere in the program.

A symbol has been defined more than once in the
source program.
E

VARIABLE FIELD

EXPRESSION

An error has been encountered in the VARIABLE field

An illegal expression has been encountered. There are

that cannot be classified more explicitly - this could be

many reasons for this error; see Section 2 for details.

a string of characters that has no syntactic meaning; or

FIELD OVERFLOW

nothing was entered in the VARIABLE field when an

A value has been formed that is too large for the

entry is required.

intended field. Examples of this are: a value of more
than one bit in the Index subfield, a value of more than

An index subfield was specified, but nothing was

4 bits in the M and N subfields, etc.

entered; or an index subfield has been encountered for

INDIRECT ADDRESSING

an instruction that does not allow indexing.

An asterisk has preceded the VARIABLE field of a
non-memory reference instruction.
M REFERENCE TO MULTIPLE DEFINITION

INDEX SUBFIELD

NON-ZERO LEVEL REDUCTION
An expression has been encountered that does not have

A multipally defined symbol has been referenced in the

matching pairs of parentheses; there must be exactly

source statement.

the same number of left and right parentheses.

2-11

LEAP
PseudoOperations

Section 3

This section contains a description of the pseudo-

code produced. In addition, pseudo-operations are provided

operations provided in the LEAP language. Examples using

for conditional assembling of source lines and setting the

the pseudo-operations are included when further clarifica-

value

tion is required.

operation is provided for defining the end of the source

Preceding each pseudo-operation description is a figure

the

LOCATION

counter.

A single pseudo-

program.

showing the format of the LOCATION, OPERATION, and
VARIABLE fields.

The pseudo-operations described in this section are:
BOOT - BOOTSTRAP FORMAT

LOCATION

OPERATION

VARIABLE

DUP - DUPLICATE NEXT SOURCE LINE
END - END OF SOURCE PROGRAM
ORG - SET PROGRAM ORIGIN
SKIPF - SKIP IF FALSE

The above figure illustrates the format; the fields cor-

SKIPT - SKIP IF TRUE

respond to the fields defined in Section 2.
Except for the TITLE and PRINT psuedo-operations,

BOOT - BOOTSTRAP FORMAT

the COMMENTS field always starts with the termination of
the VARIABLE field (the first space encountered that is

LOCATION

OPERATION

VARIABLE

normal

BOOT

ignored

not part of text data). To conserve space and the reader's
time, the COMMENTS field is not shown with each of the
pseudo-operations.
If the word "normal" appears in the LOCATION field
of the format figure preceding the pseudo-operation discus-

This pseudo-operation specifies to LEAP that the

sion, it means that entry of a symbol in the LOCATION

format of the object code produced should be the format

field is optional. If a symbol is entered in the LOCATION

recognized by the bootstrap loader and that the mode of

field, its value is assigned in the normal manner.

assembly should be absolute for the entire assembly.
There are several reasons why a programmer uses this

If the word "symbol" appears in the LOCATION field
of the format figure preceding the pseudo-operation discus-

option. Among these are the following:

sion, it means that there must be a symbol entered in the

1. The programmer is in complete control of program and
data storage in memory.

LOCATION field. If no symbol is encountered, the error
code "S" is printed on the listing.

ASSEMBLY CONTROLLING PSEUDO-OPERATIONS

All base page linkages can be assigned by the programmer.
The Bootstrap Loader program can be used to load
memory rather than the much larger Extended Loader.

The

following

paragraphs

describe

those

pseudo-

4. This also saves the added step of using the Extended

operations provided as part of the LEAP language that

Loader through its genboot option to generate boot-

allow the programmer to control the format of the object

strap object code.

3-1

The BOOT pseudo-operation causes the object program
to be completely absolute; no memory-reference instructions may make reference to relocatable or external
elements, or elements either outside the page in which the
instruction is located or the base page. If a violation of
these rules occurs, the error code "B" will be printed on the
listing with the source line in which the offending element
is encountered. When used, the BOOT pseudo-operation
must be the first source statement to be read by LEAP or it
will be considered an illegal command to LEAP and the
error code "B" will be printed on the listing with the source
line. See Section 5 for a description of the bootstrap
format.
A

summary

illegal

expression, the value of the LOCATION counter for each
duplication.
The expression must equal some finite value n. The
source statement then appears n times, not n+1 times. An
example of this pseudo-operation is found in Section 3.
When the expression equals zero, the following source line
is not assembled.
END - End of Source Program

pseudo-operations when

LOCATION

OPERATION

VARIABLE

normal

END

expression

assembling with he BOOT pseudo-operation are as follows:
1. ORG

when the expression is relocatable;

2. EXTRN

This pseudo-operation gives the programmer the capa-

3. ENTRY
4. CLEAR

bility to specify to LEAP that the end of the source program is reached and that the value of the expression in the

5. COMN

VARIABLE field defines the location of the first instruc-

6. OS
7. EQUR

when the expression is relocatable;

tion to be executed at run time. THERE MUST BE ONLY
ONE

END

PSEUDO-OPERATION

SOURCE

PROGRAM.
Each of these pseudo-operations requires either relocatable items or special type codes. Since bootstrap format

When LEAP encounters the END pseudo-operation, the
following action takes place:

requires absolute assembly and has no provision for relocation, each of these will have the "B" error code printed on

PASS 1

the listing with the source line in which they appear.
The Location Counter used for value and mode assignment is dependent on the mode of assembly at the time the

DUP.Duplicate the Next Source Line

END pseudo-operation is encountered. If LEAP is procesLOCATION

OPERATION

VARIABLE

normal

DUP

expression

sing absolute statements, the mode and value assignment is
absolute; if LEAP is processing relocatable statements, the
mode and value is relocatable.
1. The literal table is examined. For each literal found,
LEAP assigns the value and mode of the LOCATION
counter for reference during pass 2. The LOCATION

This pseudo-operation gives the programmer the capa-

counter is incremented by one for each literal; thus, the

bility to specify to LEAP that the next source statement

value assigned for later reference is actually the location

should be duplicated the number of times specified by the
expression in the VARIABLE field.
The expression in the VARIABLE field must be absolute and if any symbol appears in the expression, the
symbol must have been previously defined (no forward
reference); violation of this rule causes the error code "P"
to be printed on the listing.
If the source statement that follows the DUP pseudooperation causes object code to be generated, the LOCATION counter will be increased the appropriate amount for
3-2

each duplication. If the asterisk is used as an element in the

of the literal.
2.

LEAP now prints a message signifying the completion
of Pass 1 on the system's tele-printer, and waits for
operator action before continuing.

PASS 2
1. A listing of the literals and their values (if any exist) is
printed.
2. The literals are output in the proper object code
format.

3. A listing of all symbols and their values (in alphabetic

SKIPF - Skip If False

order) is printed if the LSTSY pseudo-operation has
been encountered.
4. The expression in the VARIABLE field is evaluated. If

LOCATION

OPERATION

normal

SKIPF

VARIABLE
first expression,

nothing is entered in the VARIABLE field, LEAP out-

second expression,

puts the END/JUMP object code and makes the address
of the jump equal to absolute zero. If an expression is
entered, the resultant value is the address of the iump.
5. An end-of-assembly message is typed on the systems

The pseudo-operation gives the programmer the capability to specify to LEAP that a portion of the program
should be conditionally excluded from the assembly
process, dependent on the first expression being false.

teleprinter.

Both of the expressions in the VARIABLE field must
be absolute. Any symbols used in the expressions must be

ORG - Set Program Origin

previously defined. If either (or both) of these conditions is

LOCATION

OPERATION

VARIABLE

normal

ORG

expression

not met, the error code "P" is printed on the listing and the
value of the first expression is set to zero (false).
When LEAP encounters a SKIPF pseudo-operation, it
evaluates the first expression in the VARIABLE field. If the
value of the expression is not zero (true), the remainder of
the line is ignored and LEAP proceeds to the next source

This pseudo-operation gives the programmer the capa-

line in the normal manner. If the value of the first expres-

bility to specify to LEAP that the LOCATION counter

sion is zero (false). LEAP evaluates the second expression.

should be set to the value of the expression in the VAR 1-

The resultant value is the number of subsequent source

ABLE field. The LOCATION counter may be set absolute

lines skipped. If the LIST pseudo-operation is in effect, the

or relocatable depending on whether the expression in the

skipped source lines are listed.

VARIABLE field is absolute or relocatable.

In the example below, the programmer specifies that

When LEAP encounters the ORG pseudo-operation, the

the 2 lines following the SKIPF should not be included in

expression in the VARIABLE field is evaluated and the

the program, if the value of the symbol, DEBUG, is zero

LOCATION counter is set to the value and mode of the

(false). If the value of DEBUG is not zero (true). the 2 lines

expression.

should be included.

When LEAP is assembl ing bootstrap formatted object

If the programmer chose not to define DEBUG, it

code, the expression in the VAR IABLE field must not be

would be a phase error (error code "P"), forcing the value

relocatable. If the expression is relocatable, the error code

of the first expression to be zero, and the next 2 lines

"B" is printed on the listing with the source statement.

would be skipped.

LOCATION
123456

OPERATION

VARIABLE

1 8 9 10 11 12 13 14 15

ItJ es UG •2.
iT'i Plr:

p" I~ S.E ~

1= r

L O~

J MM

C!0

~ ~.

I
!

'2
E

COMMENTS

132

~ BE EINI
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35
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..
;:..

m
3-3

SKIPT - Skip If True

skipped. If the LIST pseudo-operation is in effect, the
skipped source lines are listed.

LOCATION

OPERATION

normal

SKIPF

This coding form example illustrates:

VARIABLE

1. use of SKIPT and SKIPF
2. program being modified at assembly time, dependent

first expression,

on the parameter, ARG, and

second expression

3. program being modified at execution time, dependent
on the same parameter, ARG.
The following discussion explains each line of the

The pseudo-operation gives the programmer the capa-

example. Assume that ARG is defined earlier in the pro-

bility to specify to LEAP that a portion of his program

gram and that it has only four values: 0,1,2, or 3.

should conditionally be excluded from the assembly pro-

SKIPT ARG, 2*ARG

cess, dependent on the first expression being true.
Both of the expressions in the VARIABLE field must

If ARG=O, the next, and subsequent lines are assembled

be absolute. Any symbols used in the expressions must have

in the normal manner. If ARG=l, 2* ARG lines are skipped

been previously defined. If either (or both) of these condi-

(2) and assembling resumes at A 102. If ARG=2, 4 lines are

tions is not met, the error code "P'. is printed on the listing

skipped and assembling resumes at A 104. If ARG=3, 6 lines

and the value of the first expression is set to zero (false).

are skipped and assembling resumes at Al05+1.

When LEAP encounters a SKIPT pseudo-operation, it
evaluates the first expression in the VARIABLE field. If the
value of the expression is zero (false), the remainder of the

SKIPF ARG-3,9
If ARG=3, none of the lines A 100 thru A 105 are

line is ignored and LEAP proceeds to the next source line in

assembled; therefore, there is no clear loop and all lines

the normal manner. If the value of the first expression is

down to, but not including, DONE are skipped (if

not zero (true), LEAP evaluates the second expression. The

3-ARG=O, 9 'lines are skipped).

resultant value is the number of subsequent source lines

assembling resumes with the next line.

LOCATION
123456

OPERATION

Is lit ... 1t'1
iOls

4' 012.
~ I 0 I'J

~ \0 ~
~ I 0 Is

ltIJ ~ p

m
20

Dis

5 kIn

I~R G- 13:. ()

~ T~

ICIGl \JIN T

5 T~
I

Nt.

J MP
e \C.

Q, ,
I

I
I

Ci3 -~ IR~ ) jj IZ

L /"II.
T ~~

=A Ilol~

tt I

PI)

COMMENTS

132

i2. iA IR e

11
Ii
11

0 NX

Df I~ e

VARIABLE

7 8 9 10 1112 13 14 15

~ 1O 10
~ I en

If ARG=3, normal

I
I
I
I
I

I
I

ClfJ UIH T

L0 fJiP

I
I

ttt I
--

ifF--

LDI (3-ARG)*2

DATA GENERATING PSEUDO-OPERATIONS

The value loaded into the A-register (immediate) is
The pseudo-operations described in this section are:

dependent on the value of ARG. If ARG=O, the value

DC - DATA CONSTANT

loaded is 6,(3-0)*2=6 with 6 the number of locations to be

PTR - ADDRESS POINTER

cleared (if ARG=O, none of the lines A 100 thru A 105 are

TXT - CHARACTER STRING

skipped). If ARG=1, the value loaded is 4; if ARG=2, the

Because the syntax for expressions in the LEAP lan-

value is 2. If ARG=3, this instruction or the next 8 instructions are not included in the program (the SKIPF would

guage is not ambiguous, only two pseudo-operations (DC

have skipped).

and TXT) are required for generating data values within a

TWA

program. It should be noted that data of different types
(decimal, hexadecimal, USASCII, address) can be generated

This instruction forms the negative of the count for the
loop counter.

from one source line; it is not necessary to have a different
DC statement for each of the different types. Up to 7 subfields per source line can be written. The maximum number

STACOUNT
Initializes the loop counter

LDX = A105
This instruction initializes the index register to point to
the first location to be cleared.

CLA
Clears the A-register for storing into the locations to be
cleared.

LOOPSTA 0,1

or words reserved with one DC statement is 28.
It is sometimes desirable to have what may appear to be
superfluous operations; i.e., two different operations may
be used to generate the same result. This is the case with
the DC and PTR pseudo-operations. By using the DC
pseudo-operation, it is possible to duplicate any of the
capabilities provided with the PTR pseudo-operation. The
reason for having the PTR pseudo-operation is to provide a
convenient documentation aid. As a courtesy to others who
may have to understand a program, it is recommended that
the PTR pseudo-operation be used whenever an address or
indirect address constant is used. This will make it easy to
quickly differentiate between actual data and pointers to
memory locations (both of which may be data, but the
intended functions are not the same).

Clears the location pointed to by the index register

DC - Data Constant
DNX 1
LOCATION

OPERATION

normal

DC LKJ

VARIABLE

Decrements the index register by 1. Each time through
the loop, the index register points to the next location to

exp 1, exp 2, ... , expn

be cleared.
This pseudo-operation gives the programmer the capa-

INC COUNT

bility to have LEAP convert certain types of data and
Increments the loop counter by 1, making it less
negative.

expressions into the hexadecimal code used by the MAC
16.
If there is a symbol in the LOCATION field, the value

JMP LOOP

and mode of the symbol will be the value and mode of the
LOCATION counter at the time the symbol is encountered.

When the loop counter reaches 0, this instruction is

The optional OPERATION sub-field (,K) is the field

skipped and execution resumes at DONE. Otherwise, the

size (in words) that will be generated for each value and

computer will go back to LOOP for its next instruction.

may be an evaluative absolute expression (no forward or

3-5

external references) that results in an integer in the range

The DC pseudo-operation generates each value in the

1::;K:S4. If K is not in the range 1::;K~4, the error code

list into a field whose size is K words (if K is specified) or

"0" will be printed on the listing on the line of the source

one word (if K is not specified).
When the field size to be generated for each value is one

statement and K will be assumed to be 1.
The LOCATION counter will be incremented by the
value of K for each expression in the VARIABLE field of
the DC pseudo-operation.

1. Single precision fixed-point decimal data.

The expressions in the VARIABLE field must follow

Hexadecimal values of from one to four hexadecimal

the rules described in Section 2 - Expressions. Any legal

digits. If fewer than four hexadecimal digits are written,

expression may be written in the VARIABLE field. If two

the digits are right justified in a data word with leading

or more expressions are written, there must be a comma (,)

hexadecimal zeros instead. If more than four digits are

between the expressions. Up to 7 expressions can be

written, the last four are entered in a data word and the

written in the VARIABLE field.

remaining digits are truncated.

0000
0001
0002
0003
0004
0005
0006
0007
0008
0009
OOOA
OOOB
OOOD
OOOE
OOOF
0010

R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R

0011
0012
0013
0014
0015
0016
0017
0018
0019
001A

R
R
R
R
R
R
R
R
R
R

oooe

C
E
E

*1
OK

3-6

word, the expressions in the value list must be evaluated as
one of the following:

0218
FFEA
0001
0001
D3C4
00D3
0000
0218
FFFF
FFEA
0000
0001
0001
2345
0000
C5C3
0042
0010
0000
0000
0000
0010
0000
0000
0000
OC8F
4132
3D70
0000

EXAMPLE OF DC PSEUDO-OPERATION
0001 *
536., - 22., 1, $12345, , SD' , 'S'
0002 EXl
DC

0003 EX2

DC., 2

536,-22.,1.,$12345., 'LEC'

0004 EX3
0005 START
0006 EX4

DC
EQUR
DC., 2

$42R
*-1
, START"3. 14B5.,3.14

0007

END

Example:
Value
$ ABC

OABC

$12345

2345

eight digits and character strings of up to four characters
may be used.

Dataword

When K=4, double precision floating point data; hexa-

USASCII text of one or two characters. A 2-character

decimal values of up to sixteen digits and character strings
of up to eight characters are allowed.

string fills a word. A single character is placed in the
right byte of a word and zeros are placed in the left
byte. If a character string contains more than two

Examples of the DC pseudo-operation follow.

characters, an error is noted and the last two characters

\
I

are entered in the data word.

Note that in the example listing, there is an error code

"c" to

4. A symbol. The value of the symbol becomes the data
entry.

$ 12345 is incorrect because it takes more than a single

When K=2, double precision fixed point data; single

word to convert it. In Ex. 3, $42R is incorrect because 'R'

precision floating point data; hexadecimal values of up to

the left of each incorrectly converted line. In Ex. 1,

is not a legitimate hexadecimal character.

PROGRAMMER

DATE

PROGRAM
LOCATION
123456

IE )(i

OPERATION
7

Die

E)( 2

EX 3

EX ~

$ 1 2 13 45 ,1'

2 1, $ i 2 I~ 4fS tl'

$~
~-

,s ~ 11

I¢ -~ pie RA rtlI ¢~

1.5 3',-Z2
I-

l!i 3

COMMENTS

132

,25

Pl e ~ F 10 c PS

DC ,,2

srr ~ IRtf

VARIABLE

8 9 10 1112 13 J4 15

,14Ie 15

•

I
!

I
L

+Hi
I

-r

s·
I

i---

f-f-

lit

tt1 ill

T
T

I
I
I

ITT

~ !

I
3-7

PTR - Address Pointer

LISTING CONTROLLING PSEUDO-OPERATIONS

LOCATION

OPERATION

VARIABLE

normal

PTR

exp

The

following

paragraphs

describe those

pseudo-

opera.tions provided in the LEAP language to give the programmer control over the documentation of a program.
None of the pseudo-operations in this section have any
effect on the object code produced by LEAP. The pseudo-

This pseudo-operation gives the programmer the capability to generate a single word of data. Although there is
no restriction to the type of single-word data that can be
generated, it is recommended that the use of the PTR
pseudo-operation be limited to generating address or
indirect address words.

operations described in this section are:
EJECT - Skip to the top of the next page*
LIST - List during Pass 2
NLiST - Don't list during Pass 2
SPACE - Space N lines before resuming listing*
TITLE - Heading to be printed at top of page*
LSTSY - List symbol table in alphabetical order
*These pseudo-operations are not listed unless the pseudo-

TXT - CHARACTER String

LOCATION

OPERATION

normal

TXT, MM

operation is stated.
VARIABLE
Character String

EJECT - Skip To The Top Of The Next Page

LOCATION

OPERATION

VARIABLE

normal

EJECT

ignored

This pseudo-operation enables the user to assemble a
character string for use as data.
The character string is a USASCII text string as
described in Section 2. The character string is assembled in
binary-coded form, two characters per word. A blank is
inserted as the second character of the last word if the
number of characters is odd. The string can contain up to
58 ASCII characters per source statement and starts after
one blank character following MM.
Example of TXT pseudo-operation:
TXT, 11 VALUE OF XX

This pseudo-operation gives the programmer the capability to specify to LEAP that a new page of printed output
should be started before resuming the program listing.
When LEAP encounters an EJECT pseudo-operation,
the following action takes place:
1. The paper in the listing output device is spaced to the
start of the next page.
2. The heading (if any) and page number are printed at the
top of the page.
3. The paper is spaced down four lines.
4. The listing resumes.

Generates 6 words as follows:

LIST - List During Pass 2

LOCATION

OPERATION

VARIABLE

normal

LIST

ignored

X
X

This pseudo-operation gives the programmer the capaThe pseudo-operation mnemonic (TXT). the subfield

bility to specify to LEAP that the program listing should be

delimiter (comma). and the character count (MM) must be

listed on the listing device during pass 2. The LIST pseudo-

wholly contained within the operation field. Blanks within

operation is printed on the listing.

this field result in a misinterpretation of the statement and
3-8

improper object code is generated.

When

the

LIST pseudo-operation is in effect, all

skipped codes are listed (see SKIPF and SKIPT).

The program listing will continue to be produced until

TITLE - Heading to be Printed at top of Page

the N LIST pseudo-operation is encountered. If neither the
LIST nor NLiST pseudo-operations are encountered, LEAP

LOCATION

OPERATION

normal

TITLE

VARIABLE

lists the program on the listing device (see Appendix C).
'character string'

NLiST - Don't List During Pass 2

LOCATION

OPERATION

This pseudo-operation gives the programmer the capa-

VARIABLE

bil ity to specify a heading to be printed on the program
normal

NLiST

listing. The TITLE pseudo-operation is not printed on the

ignored

listing unless the LIST pseudo-operation is in effect.
When LEAP encounters a TITLE pseudo-operation, the
This pseudo-operation gives the programmer the capability to specify to LEAP that the program listing should

following action takes place:
1, All of the characters in the character string are placed in

not be listed on the listing device (during pass 2). The

the heading buffer.
2.

N LIST pseudo-operation is printed on the listing.
The program listing will continue to be inhibited until a

The action described for the EJECT pseudo-operation
takes place.
The contents of the heading buffer continues to be

LIST pseudo-operation is encountered.

printed on each page until another TITLE pseudo-operation
is encountered.

SPACE - Space n Lines Before Resuming Listing

If printing is inhibited (NLIST pseudo-operation), printLOCATION

OPERATION

VARIABLE

normal

SPACE

expression

ing does not occur, but the characters in the character
string is still placed in the heading buffer.
If no TITLE pseudo-operation is encountered in the
source program, the contents of the heading buffer
encompass all spaces.

This pseudo-operation gives the programmer the capability to specify to LEAP that the number of lines specified

LSTSY - List Symbol Table

by the expression in the VARIABLE field should be spaced
up before resuming the program listing. The SPACE

LOCATION

OPERATION

VARIABLE

normal

LSTSY

ignored

pseudo-operation is not printed on the listing unless the
LIST pseudo-operation is in effect.
The expression in the VARIABLE field must be absolute. If the expression is not absolute, the error code "E" is
printed

the

listing,

along

with

the

SPACE

pseudo-operati on.
If the listing has been inhibited (NLlST), the SPACE
pseudo-operation has no effect.
If the value of the expression in the VAR IABLE field is

This pseudo-operation gives the programmer the capability to specify to LEAP that the assembly symbol table
should be listed on the listing device (after pass 2) in alphabetical order. The LSTSY pseudo-operation is printed on
the listing.
When LEAP encounters a LSTSY pseudo-operation, the

large enough to cause spacing beyond the bottom of the

following action takes place:

current page, spacing is terminated, the action described for

1. The line in which the LSTSY pseudo-operation appears

the EJECT pseudo-operation is taken, and listing resumes in

is printed on the listing (subject to NLiST and LIST

the normal manner.

pseudo-operations).

3-9

2. An internal flag is set to denote that the LSTSY

commas)

in the VAR IABLE field.

If no symbol

encountered in the VAR IABLE field, the error code "V" is

pseudo-operation is encountered.
3. When the END pseudo-operation is encountered, the

printed on the listing.

Symbol (name or label) table is printed in alphabetical
order along with the value of each of the symbols.

The most common use for the EXTRN pseudooperation is to specify the names of subroutines referenced

EXTERNAL REFERENCE PSEUDO-OPERATIONS

within a program, but are assembled separately. The
EXTRN pseudo-operation causes the proper codes to be

It is desirable to segment programs to decrease the size
of source programs. When this is done, it is usually neces-

produced in the object code so that the Extended Loader is
able to complete linkages to subroutines.

sary to reference elements that are in another segment from

Although the use of the EXTRN pseudo-operation is

the one being assembled. The pseudo-operations described

primarily associated with subroutine reference, it is not

in this section make it possible for the programmer to con-

restricted to this. It is often desirable to reference an ele-

veniently do this.

ment or group of elements (array) that is external to the

There are two pseudo-operations provided in the LEAP
language for external reference and definition. If either (or
both) of these pseudo-operations are used in a source program, the Extended Loader must be used to load the object
code

produced

the assembly

process.

The two

pseudo-operations are:
EXTRN -

program. This can also be done by using the EXTRN
pseudo-operation.
Symbols in the VARIABLE field of an EXTRN statement may not appear as statement names in the same
program as the EXTRN statement itself. These will be
flagged with an error code E. The statement with the name

EXTERNAL SYMBOL (DEFINED OUT-

SIDE THIS PROGRAM) REFERENCE

which appears in the EXTRN statement VARIABLE field is
flagged with an error code S.

ENTRY - EXTERNAL SYMBOL DEFINITION
ENTRY - External Symbol Definition
EXTRN - External Symbol
LOCATION
normal

OPERATION
EXTRN

LOCATION

OPERATION

normal

ENTRY

VARIABLE

VARIABLE
symbol, symbol,

symbol, symbol,
..... ,symbol

... ,symbol
This pseudo-operation gives the programmer the capaThis pseudo-operation gives the programmer the capa-

bility to specify to LEAP that the symbols appearing in the

bility to specify to LEAP that the symbol (s) listed in the

VARIABLE field may be referenced externally (by other

VARIABLE field are external symbols (not defined within

programs),

the program). Programs which reference external symbols
must be loaded by the Extended Loader.
There must be at least one symbol in the VARIABLE
field; there can be as many as 7 symbols (separated with

3-10

There must be at least one symbol and, there can be as
many as 7 symbols (separated with commas) in the
VARIABLE field. If no symbol appears in the VARIABLE
field, the error code "V" is printed on the listing.

The example below is a subroutine that refers to

is external, the EXTRN pseudo-operation is used to define

another subroutine; therefore, both the ENTRY and

the external subroutine. If the EXTRN pseudo-operation is

EXTRN pseudo-operations are used.

included, the reference to SINE would have the error code
"U" printed on the listing (the symbol would have been

The subroutine is referenced externally as COSINE.
Since the subroutine is "calling" another subroutine which

undefined).

PROGRAMMER

DATE

PROGRAM

OPERATION

LOCATION

123456

IE )(1 ,

VARIABLE

7 8 9 10 1112 13 14 15

I: toe

NiAL

Er4
C~ S IINiE

1\1)1)

S ttx

L~O~

JMl
E itT «IN

T!E ftIIp

iO~

'ex ~ IN ip LE

l~il

C.IQl Is lINE

=, le2
Tf MP
SI NE
lE MP

COMMENTS

132

I
I

1
I

I
I

C!I

I
I
I
I

, "F

~
STORAGE ALLOCATING PSEUDO-OPERATIONS

pseudo-operation, except that the reserved area is cleared
(the DS pseudo-operation does not clear the reserved area).

When it is necessary to reserve an area of one or more

If a symbol is encountered in the LOCATION field, the

words for temporary or calculated values, LEAP provides

value of the symbol will be the location of the first word of

the capability of specifying that area (of any size) with just

the area to be reserved and cleared. References to the other

one source statement. This prevents forcing the pro-

words in the area must be relative to the first word.

grammer to write a line of code for each word that is to be

The value of the expression in the VARIABLE field is

reserved. Three pseudo-operations are described in the

the number of words to be reserved and cleared. The value

following paragraphs:

of the expression must be absolute, and any symbols used

CLEAR - CLEAR AND RESERVE AN AREA

in the expression must have been previously defined (no

COMN - RESERVE AN AREA IN COMMON

forward reference). If the value of the expression is not

DS - RESERVE A DATA STORAGE AREA

absolute, or if a symbol is used that has not been previously
defined, the error code "P" will be printed on the listing

CLEAR - Clear and Reserve an Area

with the line. Also, if nothing is entered for the expression,
the error code "V" will be printed.

LOCATION

OPERATION

VARIABLE

normal

CLEAR

expression

When LEAP encounters a CLEAR pseudo-operation,
the following actions take place:
1. If there is a symbol in the LOCATION field, the symbol
will be assigned the mode and value ofthe LOCATION
counter.

This, pseudo-operation gives the programmer the capability to specify to LEAP that an area of memory should be
reserved and cleared (set to zeros) at load time. The
CLEAR pseudo-operation is basically the same as the DS

2. The expression

in the VARIABLE field will be

evaluated.
3. The value of the expression in the VARIABLE field will
be added to the LOCATION counter.

3-11

Object code is produced to specify to the Extended

os -

Reserve Data Storage Area

Loader the number of words that should be cleared at
load time.

COMN - Reserve an Area in COMMON
LOCATION

OPERATION

VARIABLE

normal

COMN

expression

LOCATION

OPERATION

VARIABLE

normal

OS[,K]

expression

This pseudo-operation gives the programmer the capability to specify to LEAP that an area of memory should be
reserved at load time. The OS pseudo-operation is the same
as the CLEAR pseudo-operation, except that the reserved
This pseudo-operation gives the programmer the capability to specify to LEAP that an area of memory should be
reserved in the COMMON area.
of the symbol

will

If a symbol is encountered in the LOCATION field, the
value of the symbol will be the location of the first word of

If a symbol is encountered in the LOCATION field, the
value

area is not cleared.

the

location

the

(numerically) first wora of the area to be reserved.
References to the other words in the area must be defined
symbolically.
The value of the expression in the VARIABlE field is
the number of words to be reserved. The value of the
expression must be absolute, and any symbols used in the
expression must have been previously defined (no forward
reference). If the value of the expression is not absolute, or
if a symbol is used that has not been previously defined, the
error code "P" will be printed on the listing with the line.
Also, if nothing is entered for the expression, the error code
"V" will be printed.

the area to be reserved. References to the other words in
the area must be relative to the first word.
The optional OPERATION sub-field [,K] is the field
I

size (in words) that will be generated for the expression in
the VARIABLE field and may be a evaluatable absolute
expression (no forward or external references) that results
in an integer in the range lsKs4. If K is not specified, it
will be assumed as 1 (default condition). If K is not within
the limits of from 1 to 4, the error code 0 will be printed
on the listiRg on the line with the source statement and K
will be assumed to be 1.
The value of the expression in the VARIABLE field is
the number of fields to be reserved. The value of the
expression must be absolute, and any symbols used in the

When LEAP encounters a COMN pseudo-operation, the
following action takes place:

expression must have been previously defined (no forward
reference). If the value of the expression is not absolute, or
if a symbol is used that has not been previously defined, the
error code "P" will be printed on the listing with the line.

If there is a symbol in the LOCATION field, it will be
assigned the current value of the COMMON counter
(the COMMON counter is initialized to zero at the start
of an assembly).

2. The

expression

Also, if nothing is entered for the expression, the error code
"P" will be printed.
When LEAP encounters a OS pseudo-operation, the
following actions take place:

in the VARIABLE field will

evaluated and the resultant value will be added to the
COMMON counter.

1. If there is a symbol in the LOCATION field, the symbol
will be assigned the mode and value of the LOCATION
counter.
2. The value of K will be recorded.

The Extended Loader assigns the external location of
COMMON in memory at load time. The value assigned to

3-12

3. The expression in the VARIABLE field will be evaluated.

the symbol in the LOCATION field of a COMN pseudo-

4. The value of the expression in the VARIABLE field will

operation is actually the value of the offset from the start

be multiplied by K and added to the LOCATION

of COMMON.

counter.

·..L-O-C-A-TION-,r.......,O""P-=E-=R-A""T-,O-N-r-.-----":"""V-A-=R-:-,A:"":B::":L"":E:------.--------------C-o-M-;,:;i-ENT-S-35

In this example, the following action takes place:

SYMBOL DEFINING PSEUDO-OPERATIONS

1. Initial values:
A) LOCATION counter set to zero
B) COMMON counter set to zero
C) relocatable mode set
D) the object is defined as extended format.
2. The first line defines E as relocatable 0 (default condition is relocatable)
3. The second line sets the LOCATION counter to 07DO
(hex), absolute
4. The symbol A is assigned the absolute mode with a
value of 07DO (hex)

The pseudo-operations described in this section make it
possible for the programmer to assign values (and mode) to
symbols without necessarily relying on the value of the
LOCATION counter. The pseudo-operations discussed are:
EQU -

SYMBOL EQUALS VALUE AND MODE OF
EXPRESSED

EQUR - SYMBOL EQUALS VALUE OF EXPRESSION,
RELOCATABLE MODE

5. The LOCATION counter is increased to 0834 (hex) and
object code is produced to tell the extended loader to

REDEF - REDEFINE SYMBOL

clear from 07DO to 0833 (hex)
6. The symbol B is assigned the absolute mode with a
value of 0834 (hex)
7. The LOCATION counter is increased to 0898 (hex)

EQU - Symbol Equals Value and Type of Expression

LOCATION

OPERATION

VARIABLE

symbol

EQU

expression

8. The symbol C is assigned the absolute mode with a
value of 0897 (hex)

9. The LOCATION counter is set to relocatable 0
10. The symbol D is assigned the relocatable mode with a
value of 0000

This pseudo-operation gives the programmer the capa-

11. The LOCATION counter is increased to 0032 (hex)
12. The symbol

TEMPl

is assigned the value of the

COMMON counter (0000)
13. The COMMON counter is increased to 0001 (hex)
14. The symbol TEMP2 is assigned the value of the
COMMON counter (0001 )

bility to specify to LEAP that the symbol appearing in the
LOCA TI ON· field is to be assigned the value and mode of
the expression in the VARIABLE field.
If a symbol is not entered in the LOCATION field, the
error code "S" is printed on the listing. If no expression is
entered Oeft blank), the error code "V" is printed on the

15. The COMMON counter is increased to OOOB (hex)

listing. Any symbols used in the VARIABLE field must be

16. The sy mbol TE MP3 is assigned the val ue of the

previously defined; if not, the error code "P" will be

COMMON counter (OOOB)

printed on the listing.

3-13

EQUR - Symbol Equals Value of Expression, Relocatable

MISCELLANEOUS PSEUDO-OPERATIONS

Mode

The pseudo-operations discussed in the section are:
LOCATION

OPERATION

VARIABLE

SETB - SET THE LOADING B FLIP-FLOP
RESB - RESET THE LOADING B FLIP-FLOP

symbol

EOUR

expression

PRINT - PRINT DURING PASS 1
SETB - Set the Loading B Flip-Flop

This pseudo-operation gives the programmer the capability to specify to LEAP that the symbol appearing in the

LOCATION

OPERATION

VARIABLE

normal

SETB

ignored

LOCATION field is to be assigned the value of the ex pression in the VARIABLE field, but that the mode assignment
is relocatable.
If a symbol is not entered in the LOCATION field, the
error code "S" is printed on the listing. If no expression is
entered (left blank), the error code "V" is printed on the
listing. Any symbols used in the VAR IABLE field must be
previously defined; if not, the error code "P" will be

The SETB pseudo-operation enables the programmer to
specify to LEAP that the status of the B flip-flop is a
"one" .

1. SETB generates type code 16 (see Section 5), which is a

printed on the listing.

directive to the Extended Loader indicating that automatic depaging should be through the fixed base page

REDEF - Redefine Symbol

LOCATION

OPERATION

VARIABLE

(location 51210-102310).
If LEAP is assembling object code in bootstrap format,
SETB is used to specify to LEAP that the correct base

normal

REDEF

Symbol,

page

expression

51210-102310). Any memory reference instruction

the

program

page

·1

(locations

must reference a location either in the local page or to
page one. Otherwise, the error code "B" appears on the
The REDEF pseudo-operation, like EOU, enables the
user to define a symbol by assigning it the value and mode
of the expression in VAR IABLE field.
The REDEF pseudo-operation differs from the EOU
pseudo-operation in that any symbol defined by a REDEF
is redefined later by means of a subsequent REDEF.
If a symbol defined via a REDEF pseudo-operation is
redefined but the user writes an EOU instead of a new

listed source line.
If neither SETB nor RESB appears at the beginning of
the program, LEAP assumes that the B flip-flop is a "1"
(initial or default condition).
The extended loader's B flip-flop can also be set via the
SEX machine instruction. This instruction acts as a pseudooperation also, and generates a type code 16 on the object
tape or control error detection.

REDEF pseudo-operation, LEAP prints an "M" error code
and retains the earlier definition.

RESB - Reset the Loading B Flip-Flop

If symbol is not entered in the VARIABLE field, the
error code "S" is printed on the listing. If no expression is

LOCATION

OPERATION

VARIABLE

normal

RESB

ignored

entered (left blank), the error code "V" is printed on the
listing. Any symbols used in the variable field must be
previously defined; if not, the error code "P" will be
printed on the listing.

3-14

The

RESB instruction enables the programmer to

are generally used as an aid for programming in-line

specify to LEAP that the status of the B flip-flop is a

standard functions in which the sequence of operations

"zero".

(instructions) does not vary, but the expressions in the

RESB generates type code 17 (see Section 5) which is a

VARIABLE fields (parameters) do. This is illustrated in

directive to the Extended Loader indicating that auto-

Example 1 which defines a double precision, fixed point

matic depaging should be through the floating base page

add. (The contents of location 0 and 0+1 are added to the

(refer to MAC 16 Programmer's Manual).

contents of location E and E+1. The result is stored in

If LEAP is assembling object code in bootstrap format,

locations F and F+1. HALT is the location of the overflow

RESB is used to specify to LEAP that the correct base

error routine.)

page of the program is relative to the current LOCA-

A macro definition must precede its first calling state-

TION Counter value (refer to page control in the MAC

ment. A macro is defined when LEAP encounters the

16 Programmer's Manual).

special character

Any memory reference

# in the first column of a location field.

instruction must reference a location either in the local

This is the macro header. All statements within the macro

page or to the correct floating base page. Otherwise, the

definition are called model statements and, except for the

error code "B" will appear on the listed source line. If

last statement are terminated with the special continuation

neither SETB nor RESB appear at the beginning of the

character (;). The collection of model statements for a

program, LEAP will assume that the B flip-flop is a "1"

macro comprise the "macro skeleton". The last statement

(initial or default condition).

signals the end of the macro skeleton (by failing to have the

The extended loader's B flip-flop can also be reset via

continuation character).

the REX machine instruction. This instruction acts as a
pseudo-operation also, and it generates a type code 17 on
the object tape.

Parameters
The parameters of a macro are the operands of the
reference or calling statement. Within a macro definition,

PRINT - PRINT During Pass 1
LOCATION

OPERATION

normal

the parameters are represented by the special character
pound sign (#) followed by either a number or an asterisk
VARIABLE
'character string'

followed by a number e.g. #2 or #*2. Since macros are positional rather than key-word, #1 refers to the first parameter
on the reference statement, #2 refers to the second parameter on the reference statement, etc. #* 1 refers to the

This pseudo-operation gives the programmer the capability to

have the remarks specified by the USACII

character string printed on the systems teleprinter during
pass

No object code is generated by the PR I NT

pseudo-operation.
The characters in the character string of the source line
are printed on the teleprinter as they are; no scan takes
place. Assembling continues with the next source line in the
normal manner.

indirect attribute associated with the first parameter on the
reference statement, #*2 refers to the indirect attribute
associated with the second parameter on the reference
statement, etc. I n a model statement, a reference to a
parameter may be written anywhere an item of an expression can be written. However, parameter references are
meaningful only within the VARIABLE or OPERAND field
of the model statement.
The values of the parameters will normally be different
each time the macro is called or referenced. Macro definitions and references need not agree in number of param-

MACRO Definition

eters. However, parameters not defined on the reference
line will have the value zero. The error code "A" will

A macro is a group of one or more statements inserted
whenever a corresponding macro reference or call occurs.

appear on the listing if no parameters appear on the
reference line.

Macros are, in a sense, analogous to subroutines which can

A macro is referenced or called by writing the name of

be called by a reference or calling statement. Like a sub-

the macro in the OPERATION field of a statement. The

routine, a macro has a name by which it is called. Macros

VARIABLE field of the calling statement will contain the

3-15

parameters to the macro. If more than one parameter is to

In this example, argument substitutions are made. When

be supplied to the macro, the parameters are written one

the macro name DADD is encountered in the OPERATION

after the other, separated by commas. The last parameter is

field, the object code corresponding to the following source

not followed with a comma. The maximum number of

lines is inserted in its place:

parameters capable of being passed to the macro is seven.

REX

C, V

LDA

D+1

ADD

E+1

Parameter substitution is positional rather than key-

STA

F+1

word, i.e., the first parameter is equated to (#1) in the

LDA

#2',

ADC

etc. Other symbols besides those used as parameters in
macro calls may also be included in macro definitions. In

ADD
STA

addition, the reserved symbols C,V,R,S,B, and H may be

SNV

used in a macro as in example 1, where C and V are used.

JMP

macro expansion, the second parameter is equated to

LOCATiON

VARIABLE

OPERATION
20

E
F
HALT
COMMENTS
50

-r~-+-r+-r+-r+-r+-r;-~-r~~-r+-r+-r;-~-r+-r+~;-+4-+-+-r

H=-1-LF~4=f=4-+-+-+--+-+-+-+-+--I-4--JH .J-

f++-++-t-HI-'-f'-t--t-'-H-t'-+-++-++~-'I-'-l.:::.pH-'=t-=-t'--!=l"'+--""+-++-t-+--l-+-f-+-+-++-+++-+-+-4--JI-I-+-HJ.
.J-..JI.....L.-L.-l.-I.--I.--l--1-.L-1-I--L-L-J.--l--'--'--I-L-I_J •.

3-16

..1

If the following code had been written, using the above macro definition:

1 8 9 10 1112 13 14 15

la I~P

COMMENTS

VARIABLE

OPERATION

LOCATION
123456

132

12
Is
,.AI.

O~ olt

LP A

I
II'

"IA Ltr

«,

I
I

The JMP' *+2 instruction would cause a jump to the

the following coding is generated:

second word of the macro definition, not the source line

LDA

ALPHA

following the DADD operation. For this reason, it is recom-

STA

BETA

mended that relative notation not be used preceding macro

When the MOVE MACRO IS CALLED BY;

calls, especially, if the programmer has macro definitions

MOVE 5, ALPHA, BETA

that generate more than one instruction.

the following coding is generated:
LDX

LDA

ALPHA, 1

macro is called by:

STA

BETA, 1

MOVE 1, ALPHA, BETA

JMP

This macro uses SKIPT and SKIPF. When the MOVE

DNX

LOCATION
I 2 3 4 5 6

OPERATION
7

8 9 10 1112 13 14 15

lEX AM PL E Z

~
I

!TH I~ I.., AC Ii< 125

Ahl ~ T~ Er2·

LD ~
S
S
L

L alA
~ IT~

Ie 1~11
J iN P

ttt

M~ vI:.

Tll E F f6
WI .. ~I\ itt. Ir

~ IdT "'iT

~iQ Eli.
"
I
I: n:

rl~

III 2 i

~3
)
~I
I
=:fI: ii
M~ It I )
It I, I. I. i
1.1 )

I-

~IF

IE L ~Ic IIC !R

lellIs I.oJk

It: I J i) I I" I~ :i

~ 13

l- f-

OJN E MEM ~It

'~ ~U~

~
~I~ ViE

COMMENTS
132

5T rI1r.l lr:.r:

VARIABLE
25

* -3

I
I

-I-fI-f-

•

I
I
r
I

=ttt

-Ht

I
I
I
I

ill

r'-

3-17

Example 3 illustrates a technique of microcoding the
MAC 16 through LEAP. When LEAP encounters "TAL14"

This particular instruction could have been generated by
"TAL9". The purpose of generating the new operation
code

is for ease

documentation.

This particular

in the OPE RATI ON field of a source line, it generates

instruction will logically OR the contents of the A register

object code of type 1 (see Section 5) consisting of 0589.

Into register L 1 and L4.

PROGRAMMER

DATE

PROGRAM
LOCATION
123456

~ERAT~
8 9
11 12 13 14 15

VARIABLE
20

l(}

132

E"" 1.6 lulc LIE

JH ~ ~
~Ir All- I~

I)~

1\1 IA t' 12 ~ bEI~ l NIEls
~b 5

Hi
PE

R~IT 1~ tl ~ ~ DIE

I
I

3-18

COMMENTS
35

ceO

Section 4

Assembling
MAC 16
Instructions

This section contains information on the assembly

current page or the base page. In the bootstrap format, any

process performed by LEAP when the mnemonic for a

reference outside the current page causes the error code

MAC 16 instruction is encountered in the OPERATION

"B" to be printed on the listing.

field. The process performed by LEAP varies with the type

The address subfield is terminated with either a blank

of instruction encountered. The six classifications of MAC

character or a comma (,). If a comma is encountered, the

16 instructions are:

next subfield is evaluated for indexing. The value of the

CLASS 0: 16 BIT, UNMODIFIED

the address subfield, the error code" A" is printed on the

index subfield is treated modulo 1. If nothing is entered in
listing.
No entry is allowed in the VARIABLE field on this
class of instructions. If any entry is encountered, the error
code "V" is printed on the listing. The following instructions are in Class 0:
ABA - Absolute Value of A
ADC - Add Carry to A
CLA - Clear A
HLT-Halt
JMA - Jump Direct Thru A
LSB - Load A (0-5) with status of C,V,R,S,B and H
NOP - No Operation
ONA - One's Complement of A
SSB - Store AO-5 into status bits C,V,R,S,B and H
TLA - Transfer Level to A
TSA - Transfer Switches to A
TWA - Two's Complement of A

The following instructions are in Class 1:
ADD - Add Memory to A
ANA - AND memory with A
CAA - Compare A with Memory Arithmetically
INC - Increment Memory and Skip if Zero
JMM - Jump and Mark
JMP - Jump
JR L - Jump and Reset Level
LOA - Load A from Memory
LOX - Load I ndex from Memory
ORA - OR from Memory to A
STA - Store A in Memory
STL - Store Left Byte of A in Memory
STR - Store Right Byte of A in Memory
STX - Store I ndex in Memory
SUB - Subtract Memory from A

XXA - Exchange I ndex and A
MPY - Multiply A

CLASS 2: I/O INSTRUCTIONS

DIV - Divide A
This class of instructions requires a subfield for both
CLASS 1: MEMORY REFERENCE

the M and N fields. If either the M or N subfield is omitted,
the error code "V" will be printed on the listing. Values in

This class of instructions is the only class that allows

either subfield are evaluated modulo 16. If either of the

indirect addressing and indexing. The first subfield in the

values is too large (more than 4 bits), the error code "F" is

VARIABLE field is evaluated and a 16-bit address is pro-

printed on the listing. The M subfield is equivalent to the

duced, if in the extended format; if in the bootstrap for-

address subfield of a memory reference instruction, and the

mat, the address is checked for reference outside the

N subfield is equivalent to the index subfield.

4-1

ARI - Arithmetic Right Shift & Insert

The following instructions are in Class 2:
EAI - External Address In

ARS - Arithmetic Right Shift

ECO - External Command Out

DNX - Decrement Index and Skip on Zero

EDI - External Data In

INX - Increment Index and Skip on Zero

EDO - External Data Out

JIX - Jump Indirect Thru Index

ESI - External Status In

JMX - Jump Direct Thru Index

CLASS 3: SKIP INSTRUCTIONS

Index

LAX - Load A Direct from Memory Location Specified by
LI X This class requires an entry in the VARIABLE field. If

Load A I ndirect from Memory Location Specified

by Index

nothing is encountered, the error code "V" is printed on

LLC - Logical Left Shift, Closed

the listing. The VARIABLE field is evaluated in the follow-

LLI - Logical Left Shift & Insert

ing manner:

LLN - Logical Left Shift, No Change to C

1. If the value in the VARIABLE field is in the range of

to 15 inclusive and the mode is absolute, the value is
2.

LLO - Logical Left Shift, Open
LRC - Logical Right Shift, Closed

inserted directly into the N field of the instruction.

LR I - Logical Right Shift & Insert

If the value in the VARIABLE field is greater than 15

LRN - Logical Right Shift, No Change to C

or the mode is relocatable, it is assumed to be a mem-

LRO - Logical Right Shift, Open

ory address. LEAP computes the N value required to

SAX - Store A in Location Specified by Index

skip to the specified memory location (forward only).

SIX - Store A Indirect thru Location Specified by Index

If the resulting value is larger than 4 bits, the error code

TAL - Transfer A to L Register

"F" is printed on the listing; the value is truncated to 4

CLASS 5: IMMEDIATES

bits and inserted into the instruction's N field.
The following instructions are in Class 3:

This class of instructions requires an entry in the

SAG - Skip if A is Greater than Zero

VARIABLE field. If nothing is encountered, the error code

SAN - Skip if A is Negative

"V" is printed on the listing. The VARIABLE field is

SAZ - Skip if A is Zero

evaluated modulo 256; if the value is greater than 255

SKN - Skip if A is Normalized

(more than 8 bits), the error code "F" is printed on the

SKP - Skip Unconditional

listing.

SKX - Skip if Index is Zero

The following instructions are in Class 5:

SLZ - Skip if Least-Significant Bit of A is Zero

ADI - Add I mmediate to A

SNB - Skip if Base Page Control is Zero

LDI - Load A Immediate

SNC - Skip if C is Zero

SBI - Subtract Immediate from A

SNH - Skip in Interrupt Not Inhibited
SNV - Skip if V is Zero
SNR - Skip if R is Zero
SNS - Skip if S is Zero

CLASS 4: N FI ELD
This class requires an entry in the VARIABLE field. If

This class of instructions requires an entry in the VAR 1ABLE field. If nothing is encountered, the error code "V"
is printed on the listing. The VA R I AB LE field is evaluated
modulo 64; if the value is greater than 63 (more than 6
bits). the error code "F" is printed on the listing.

nothing is encountered, the error code "V" is printed on

The following instructions are in Class 6:

the listing. The VARIABLE field is evaluated modulo 16; if

SEX - Set Sense Indicator

the value is greater than 15 (more than 4 bits). the error

REX - Reset Sense I nd i cator

code "F" is printed on the listing. The following instruc-

4-2

CLASS 6: STATUS MODIFIERS

For these instructions, the indicators may be repre-

tions are in Class 4:

sented by any combination of the reserved symbols

ALI - Arithmetic Left Shift & Insert

C,V ,R ,S,B and H. When writing the indicators on a coding

ALS - Arithmetic Left Shift

sheet, they are separated by commas

Section 5

SOURCE PROGRAM PREPARATION

Input/Output

Page Format

This listing is printed on continuous form paper. If the

If cards are not used for the source program, prepare a
paper tape according to the following instructions:

teleprinter is being used, the output routine keeps a line
count so that spacing is in 11 inch increments. The follow-

Preamble-Start-Of-File

ing are the specifications for the page format. There are a
total of 66 lines on an l1-inch page (6 lines per inch).

The preamble character ($81) must be used. It is
formed (on TTY) by simultaneously depressing the CTRL
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