Q.Mention the different types of addressing modes.

An addressing mode is the way an instruction specifies where its operand (data) is located, and the 8051 provides five such ways. …

[!TLDR]

The 8051 has five addressing modes — register, direct, immediate, indirect, and base-plus-index — and the first four are the ones commonly used.

Addressing modes define the way in which the operands are accessed by an instruction. Since the CPU may store data in registers, in internal memory or in an external source, it needs different ways of pointing to that data — and those ways are the addressing modes. (In the 8051, instructions are written with the destination address named first, followed by the source address.)

The five addressing modes are:

1. Register addressing mode — the operand is in a register such as A, R0–R7, DPTR, e.g. MOV A, R0.
2. Direct addressing mode — the operand is named by its single-byte RAM/SFR address, e.g. MOV A, 40H.
3. Immediate addressing mode — the operand (a constant) is part of the instruction, preceded by #, e.g. MOV A, #25H. …