HLASM Language Reference

How to Write Macro Instructions
Chapter 8. How to Write Macro Instructions
This chapter describes macro instructions; where you can use them and how you
specify them.
The first section on page 297 describes the macro instruction format, including
details on the name, operation, and operand entries, and what is generated as a
result of a macro instruction.
“Sublists in Operands” on page 304 describes how you can use sublists to specify
several values in an operand entry.
“Values in Operands” on page 307 describes the values you can specify in an
operand entry when you call a macro definition.
“Nesting Macro Instruction Definitions” on page 311 describes how you can use
nested macro call instructions to call macros from within a macro.
What is a Macro Instruction: The macro instruction provides the assembler with:
The name of the macro definition to process
The information or values to pass to the macro definition
This information is the input to a macro definition. The assembler uses the
information either in processing the macro definition, or for substituting values into
model statements in the definition.
The output from a macro definition can be:
A sequence of statements generated from the model statements of the macro
for further processing at assembly time.
Values assigned to global-scope SET symbols. These values can be used in
other macro definitions and in open code (see “SET Symbols” on page 319).
Where Macro Instructions Can Appear: A macro instruction can be written
anywhere in your program, provided the assembler can find the macro definition.
The macro definition can be found either in a macro library, or in the source
program before the macro instruction, or be provided by a LIBRARY user exit.
However, the statements generated from the called macro definition must be valid
assembler language instructions and allowed where the calling macro instruction
appears.
Macro Instruction Format
►►──┬─────────────────┬──operation_code──┬─────────────┬───────────►◄
├─name_field──────┤
│ ┌─,───────┐
│
└─sequence_symbol─┘
└── ▼ ─operand─┴─┘
name_field
is a special positional operand that can be used to pass a value into the called
macro definition. For a detailed description of what form name_entry can take,
see “Name Entry” on page 299.
© Copyright IBM Corp. 1982, 2004 297