|Noun||1.||operation code - the portion of a set of operation descriptions that specifies the operation to be performed; the set of operations in a computer|
Synonyms: order code
|(programming)||operation code - (Or "op code") 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
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.