Microassembler

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A microassembler (sometimes called a meta-assembler) is a computer program that helps prepare a microprogram to control the low level operation of a computer in much the same way an assembler helps prepare higher level code for a processor. The difference is that the microprogram is usually only developed by the processor manufacturer and works intimately with the hardware. The microprogram defines the instruction set any normal program (including both application programs and operating systems) is written in. The use of a microprogram allows the manufacturer to fix certain mistakes, including working around hardware design errors, without modifying the hardware. The use of microprogram also allows the same hardware to run different instruction sets. The microprogram is then loaded to a control store to become part of the logic of a CPU's control unit.

At one time it was proposed to provide a microassmbler to certain sophisticated users so they could customize the instruct set of the computer for their special needs, intending to provide more efficient instructions tuned to the end user's needs. The extreme complexity of writing microcode, combined with the fact that running a custom microcode prevented using commercial software, resulted in this being abandoned.