Microprogram

microprogram [¦mī·krō′prō·grəm]

(computer science)

A computer program that consists only of basic elemental commands which directly control the operation of each functional element in a microprocessor.

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Microprogram 

an associated set of microinstructions in digital computers. Each microinstruction indicates the machine micro-operations or micro-orders, the address of the next microinstruction, the duration of the microinstruction itself, and special actions relating to test operations. One microprogram can call out another as a microsubroutine. By changing the sequence and composition of the microinstructions—that is, by altering the structure of a microprogram—the system of instructions for a digital computer can be changed, thus adapting it to a certain class of problems or providing program compatibility with another digital computer.

Microprograms are usually stored in a specialized memory, which responds more rapidly than a direct-access memory. The length of a microprogram is usually 10–100 microinstructions, and a microinstruction requires 16–100 or more binary digits. The length of a microprogram in small digital computers is 256–1,024 16-digit words; in medium and large computers it is 1,024–8,196 words of 50 to 100 digits each.

REFERENCES

Boulaye, G. Mikroprogrammirovanie. Edited by M. D. Pebart. Moscow, 1973. (Translated from French.)

A. V. GUSEV