Repeat instruction
| Machine code |
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| General concepts |
| Instructions |
In computer instruction set architectures (ISA), a repeat instruction is a machine language instruction which repeatedly executes another instruction a fixed number of times, or until some condition is met.
Since it is an instruction that operates on other instructions like the execute instruction, it has been classified as a meta-instruction.[1]
Computer models
The Univac 1103 (1953) includes a repeat instruction (op code mnemonic: RPjnw) which executed the following instruction a fixed number of times, possibly incrementing one or both of the address fields of that instruction.[2] This compensated for the architectures lack of index registers.[3]
The GE-600/Honeywell 6000 series (1964) supports a single-instruction repeat (RPT), a double-instruction repeat (RPTD), and a linked-list repeat (RPL).[4][5]
Semantics
The instruction to be executed follows the repeat instruction. Fields in the instruction determine the loop termination condition.[5]
Notes
- ^ Rossman, George E. (December 1975). "A Course of Study in Computer Hardware Architecture". IEEE Computer. 8 (12): 44–63. doi:10.1109/C-M.1975.218835., p. 50
- ^ Reference Manual: Univac Scientific 1103A Computer (PDF). Remington Rand Univac. 1956. p. 30.
- ^ Conrad Weisert, "Simulating an Obsolete Computer in 1960", Part 1: The main processor [1]
- ^ GE-635 System Manual (PDF). General Electric Computer Department. July 1964. p. A-6.
- ^ a b GE-625/635 Programming Reference Manual (PDF). General Electric Information Systems. July 1964.