Note for System Programming - SP by Anantharaj Manoj

Topics ( 7 )

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Macro Processors 1

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Macro Instructions A macro instruction (macro) » It is simply a notational convenience for the programmer to write a shorthand version of a program. » It represents a commonly used group of statements in the source program. » It is replaced by the macro processor with the corresponding group of source language statements. » This operation is called “expanding the macro” 2

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Macro Instructions » A macro processor is essentially involve the substitution of one group of characters or lines for another. » It doesn‘t concern the meaning of the involved statements during macro expansion » This means the design of a macro processor is not directly related to the architecture of the computer i.e. machine independent. – For example: Suppose it is necessary to save the contents of all registers before calling a subroutine. – This requires a sequence of instructions. – We can define and use a macro, SAVEREGS, to represent this sequence of instructions. 3

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The handling sequence of the program 4