opcode

This term is a technical contraction of operation code, used exclusively within the domain of computer architecture and low-level programming. It refers to the specific binary pattern that tells a CPU exactly which hardware circuit to activate for a given instruction, such as moving data or performing arithmetic.

Because it describes a discrete unit of a machine instruction, it is treated as a standard countable noun. In technical documentation, it is frequently paired with terms like operand or instruction set to describe the full anatomy of a command.