Opcode

Most people who have been involved in MIDI sequencing for the last decade are familiar with the name Opcode, as the company (acquired by Gibson in 1998) that made Vision, OMS, and Galaxy software as well as the Studio 5 MIDI interface. However, in computer science, an opcode is the portion of a machine language instruction that specifies the operation to be performed, or to put it simply, the opcode tells the computer what to do. The term is an abbreviation of Operation Code. In terms of language, it helps to think of the opcode as the verb, and the operands as nouns. For example, in the expression 5 + x, 5 and x are the operands, and + (addition) is the operator. The operands upon which opcodes operate may, depending on CPU architecture, consist of registers, values in memory, values stored on the stack, I/O ports, the bus, and etc. The operations an opcode may specify can include arithmetic, data copying, logical operations, and program control.