Instruction - Operand

Operand are the arguments of an instruction (ie they are the data source)

The data for a source operand can be located in:

• a register,
• a memory
• the instruction itself (called immediate value) - ie an immediate value is also called an immediate operand.
• an I/O port

When an instruction returns data to a destination operand, it can be returned to:

• a register
• a memory location
• an I/O port

A register

memory location:

• Memory Segment - Offset - (Relative|Effective) address
• Memory - Physical Address

An addressing mode specifies how to calculate the effective memory address of an operand.

When the value of the operand is in the instruction itself, it's called an immediate operand or immediate value.

The size of the operand

The more operands, the more complicated is the device. See Instruction_set_architecture

• Intel 64 and IA-32 Architectures - Chapter 3.7 - Operand Addressing - Basic Execution Environment