HLASM Language Reference

Introduction to Macro Language
generation, do not generate assembler language statements, but do only internal
processing.
A macro definition provides the assembler with:
The name of the macro
The parameters used in the macro
The sequence of statements the assembler generates when the macro
instruction appears in the source program.
Every macro definition consists of a macro definition header statement (MACRO), a
macro instruction prototype statement, one or more assembler language
statements, and a macro definition trailer statement (MEND), as shown in
Figure 62.
┌──────────────────────────────► MACRO
│
┌────────────────────────────────────────────┐
│ Prototype │ &LABEL MACID &PARAM1,&PARAM2 │
│ │ └─┬─┘ └──────┬──────┘ │
│ │ ▌2▐ ▌3▐ │
│
┌ ├────────────────────────────────────────────┤
│ │ │ │
▌1▐ ││ │
│ │ │ │
│ ▌5▐─┤ │ Body of macro │
│ │ │ │
│ │ │ │
│ │ │ │
│
└ └────────────────────────────────────────────┘
└──────────────────────────────► MEND
▌4▐
┌───────┴───────┐
Macro instruction MACID OPERAND1,OPERAND2
Figure 62. Parts of a Macro Definition
The macro definition header and trailer statements (MACRO and MEND)
indicate to the assembler the beginning and end of a macro definition (see ▌1▐
in Figure 62).
The macro instruction prototype statement names the macro (see ▌2▐ in
Figure 62), and declares its parameters (see ▌3▐ in Figure 62). In the operand
field of the macro instruction, you can assign values (see ▌4▐ in Figure 62) to
the parameters declared for the called macro definition.
The body of a macro definition (see ▌5▐ in Figure 62) contains the statements
that are generated when you call the macro. These statements are called
model statements; they are usually interspersed with conditional assembly
statements or other processing statements.
Model Statements
You can write machine instruction statements and assembler instruction statements
as model statements. During macro generation, the assembler copies them exactly
as they are written. You can also use variable symbols as points of substitution in
a model statement. The assembler enters values in place of these points of
substitution each time the macro is called.
Chapter 6. Introduction to Macro Language 239