(Always “op code” when spoken) The part or parts of a machine language instruction which determines what kind of action the computer should take, e.g. add, jump, load, store. In any particular instruction set certain fixed bit positions within the instruction word contain the op code, others give parameters such as the addresses or registers involved. For example, in a 32-bit instruction the most significant eight bits might be the op code giving 256 possible operations.
For some instruction sets, certain values in the fixed bit positions may select a group of operations and the exact operation may depend on other bits within instruction word or subsequent words.
When programming in assembly language, the op code is represented by a readable name called an instruction mnemonic.
- Operation desert storm
noun 1. the codename for the US-led UN operation to liberate Kuwait from Iraq (1991)
[op-uh-rey-shuh-nl-iz-uh m] /ˌɒp əˈreɪ ʃə nlˌɪz əm/ noun, Philosophy. 1. the doctrine that the meaning of a scientific term, concept, or proposition consists of the operation or operations performed in defining or demonstrating it. /ˌɒpəˈreɪʃənəˌlɪzəm/ noun 1. (philosophy) the theory that scientific terms are defined by the experimental operations which determine their applicability
- Operation overlord
noun 1. the codename for the Allied invasion (June 1944) of northern France
- Operation sealion
noun 1. the codename for Hitler’s proposed invasion (1940) of Great Britain