What is Macro & Macro Processor in System Software and Compiler?

Macro & Macro Expansion
*******

• Macro works same as subroutine or a function which is used repeatedly whenever we required. Macro definition paced at starting of the program and Macro definition is started using word MACRO and end with word MEND.

• Each macro should have a unique name.

• Below is an example of Macro.

           MACRO ----> From here macro has started.        
             INCR &X,&Y ----> This is the declaration of prototype statement of Macro.

             LOAD  &X   ___

             ADD    &Y          |------>

             STORE &X   ___|------> This is the Macro definition. 

        MEND                

• Now we can use INCR macro in assembly langunage, the assembler will automatically place the LOAD, ADD & STORE opcode with its operand.
• e.g.

         INCR A,B ---> this statement will do three things instead of INCR A,B

                                  LOAD A 

                                  ADD B

                                  STORE A   

• The above statement is called Macro Expansion.