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Unformatted text preview: a few dozen, or a few hundred, assembly language
Assembly Languages with Macro Instructions
In general, assembly languages are termed one-for-one in nature, that is, each
assembly language instruction will result in one machine language instruction.
However, quite often a certain set of machine language or assembly language
instructions have to be used over and over. For example, three instructions, one
after the other, might be needed to print out a value on a particular computer.
These three instructions, always in the same order, might be used over and over in
the same program. Instead of forcing the programmer to write out the set of three
instructions every time he/she wants to print a value, we might as well design the
assembler (program) in such a way so as to take care of these instructions. Every
time the programmer gave the PRINT instruction, for example, the assembler
would translate it into three machine language instructions instead of one, thus
supplying the complete set of instructions required for printing.
Any instruction, such as PRINT, which gets translated into several machine
language instructions, is called a macro instruction. There might be many such
macro instructions permitted by a particular assembler. Thus, to speed up the
coding process, assemblers were developed that could produce a variable amount
of machine language instructions for each macro instruction of the assembly
The use of macro instructions adds much work to the computer because the
translation process becomes more than just changing each word into a number.
The assembler must be able to supply the missing steps as well, but it means a
tremendous saving of work for the programmer. The programmer gets relieved of
the task of writing an instruction for every machine operation performed. Thus the
use of macro instructions reduces the length of the programs, cuts down on errors,
and simplifies programming.
The macro instruction capability was developed very early in t...
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This document was uploaded on 04/07/2014.
- Spring '14