operation code

operation code
    n 1: the portion of a set of operation descriptions that
         specifies the operation to be performed; the set of
         operations in a computer [syn: {operation code}, {order
         code}]
    

operation code

   <programming> (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
   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}.

   (1997-02-14)