Which addressing mode specifies the actual operand value directly within the instruction itself, rather than referring to a memory location or register?

In Immediate Addressing, the operand is a constant value embedded directly in the instruction itself, so no memory or register access is needed to fetch it — making it the fastest addressing mode. Direct Addressing specifies a memory address containing the operand. Indirect Addressing specifies a memory location that itself contains the address of the operand. Register Addressing specifies a register holding the operand, and Indexed Addressing computes the operand's address using a base address plus an index register's value.