Page 97 - DCAP507_SYSTEM_SOFTWARE

Unit 7: Macro Language

7.1 Macro Instructions Notes

A macro instruction (macro) is just a notational expediency for the programmer to write a
shorthand edition of a program. It symbolizes a usually used group of statements in the source
program. It is substituted by the macro processor with the equivalent group of source language
statements.

Did u know? The above explained operation is known as "expanding the macro".

Example: Suppose it is essential to save the contents of all registers before calling a
subroutine. This needs a series of instructions. We can define and utilize a macro, SAVEREGS, to
signify this sequence of instructions.

7.1.1 Macro Processor

A macro processor functions fundamentally engross the replacement of one group of characters
or lines for another. Usually, it performs no analysis of the text it manages. It doesn't regard the
meaning of the involved statements throughout macro expansion. Thus, the design of a macro
processor usually is machine independent.

Notes Macro processors are used in assembly language, high-level programming
languages, e.g., C or C++, OS command languages, and universal purpose.

7.1.2 Format of Macro Definition

A macro can be defined as follows MACRO - MACRO pseudo-op displays beginning of macro
definition. Name [List of Parameters] - Macro name with a list of formal parameters.
…….
……
.……. Sequence of assembly language instructions.
MEND- MEND (MACRO-END) Pseudo displays the end of macro definition.

Example:

MACRO
SUM X,Y
LDA X
MOV BX,X

LDA Y
ADD BX
MEND

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