4. Opcodes and Operands

An opcode is short for 'Operation Code'.

An opcode is a single instruction that can be executed by the CPU. In machine language it is a binary or hexadecimal value such as 'B6' loaded into the instruction register.

In assembly language mnemonic form an opcode is a command such as MOV or ADD or JMP.

For example

MOV AL, 34h

The opcode is the MOV instruction. The other parts are called the 'operands'.

Operands are manipulated by the opcode. In this example, the operands are the register named AL and the value 34 hex.