n. (context computing English) A mnemonic used to refer to a microprocessor instruction in assembly language.
In computing, an opcode (abbreviated from operation code, also known as instruction syllable or opstrings.) is the portion of a machine language instruction that specifies the operation to be performed. Beside the opcode itself, most instructions also specify the data they will process, in the form of operands. In addition to opcodes used in the instruction set architectures of various CPUs, which are hardware devices, they can also be used in abstract computing machines as part of their byte code specifications.