Coding Procedures; Instruction Format - Control Data 3100 Reference Manual

BASIC FORTRAN II
BASIC FORTRAN II is a problem-oriented language that performs familiar mathe-
matical operations in arithmetic expressions and replacement statements. The source
language provides substantial power and flexibility through a variety of statements.
BASIC FORTRAN II is compatible with other FORTRAN II systems.
BASIC Utility
This package is similar to the 3100, 3200, 3300 Utility but incorporates its own loader
and input/output control routine.
CODING PROCEDURES
COMP ASS subprograms are written on standard coding sheets. A subprogram consists
of symbolic or octal machine instructions and pseudo instructions. Symbolic machine
instructions are alphabetic mnemonics for each of the machine instructions. Pseudo
instructions are COMPASS instructions used for the following operations:
• Subprogram identification and linkage
• Data definition (constants conversion)
• Data storage
• System calls
• Assembler control
• Output listing control
• Macro definition
INSTRUCTION FORMAT
A COMPASS instruction may contain location, operation code, address, comment, and
identification fields.
Location Field
A symbol in the location field (LOCN) is placed in columns 1-8. A symbol identifies the
address of an instruction or data item.
Location field symbols may be blank or consist of one to eight alphabetic or numeric
characters; the first character must be alphabetic. Embedded blanks are illegal in loca-
tion symbols. The following are examples of location symbols:
A
H3
ABCDEFGH
P1234567
A single
*
in column 1 of the location field signifies a line of comments.
Operation Code Field
The operation code field (OP) consists of any of the mnemonic or octal instruction codes
with modifiers, or any macro or pseudo instructions. The field begins in column 10 and
ends at the first blank column. If a modifier is used, a comma must separate the opera-
tion code from the modifier; no blank columns may intervene. A blank operation field
or a blank in column 10 results in a machine word with zeros in the operation field.
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