Computer Hardware Terms, Glossary and Dictionary

Microcode, also known as microprogram, refers to the instruction set of a CPU as a sequence of microcode instructions (microinstructions), each of which typically consists of a number of bit fields and the address of the next micro-instruction to execute. Micro-code is the translation layer between machine instructions and the elementary operations of a computer. Micro-code is stored in ROM and allows the addition of new machine instructions without requiring that they be designed into electronic circuits when new instructions are needed. Several micro-instructions will usually be required to fetch, decode and execute each machine code instruction. The elements composing the micro-program/micro-code exist on a lower conceptual level than the more familiar assembler instructions. Each element is differentiated by the "micro" prefix to avoid confusion: micro-program, micro-code, micro-instruction, micro-assembler, etc.

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microcode