Machine Level Instructions (in the General Model)

Although different computer processors will have very different instruction formats, some common elements appear in the instruction formats for virtually all computers. Specifically, computer instructions are composed of an operation code ("opcode") and one or more operands. A single operand may be a constant value, a register identification code, or the address of a location in memory or of an I/O device.

Instruction Components

An instruction is made up of an Operation Code, or "opcode", and some number of operands.

Fixed vs. Variable Length Instructions