Reference Guide

20 Chapter 2
Program Structure
The machine instruction mnemonics and completers are described in the
PA-RISC 1.1 Architecture and Instruction Set Reference Manual and
PA-RISC 2.0 Architecture.
The operands field follows the opcode field, separated by a blank or tab.
Operands are separated by commas. The meaning of the operands
depends on the specific statement type, determined by the opcode.
The number of operands permitted or required depends upon the specific
instruction.
The comments field is introduced with a semicolon, and causes the
Assembler to ignore the remainder of the source line. A comment can
appear on a line by itself.
The following listing contains several assembly language statements.
The headings identify the four fields.
Statements are normally written on separate lines. It is sometimes
useful, especially when using a macro preprocessor, to be able to write
several statements on one line. This can be done by separating the
statements with the “!” character. When this feature is used, a label can
be placed only on the first statement of the line, and a comment can only
follow the last statement on the line. The .LABEL directive can override
this condition by providing a means for declaring a label within a
multi-statement line.
Label Opcode Operands Comments
JAN .EQU 1 ;declares a symbolic constant
SUM .WORD 0 ;reserve a word and set to zero
LOOP LDW 4(%r1),%r2
ADD %r2,%r3,%r4
STW %r4,SUM-$global$(%dp)
BL LOOP,%r0