ADDRESSING MODE
Addressing modes are an aspect of the instruction set architecture in most central processing unit (CPU) designs. The various addressing modes that are defined in a given instruction set architecture define how machine language instructions in that architecture identify the operand (or operands) of each instruction. An addressing mode specifies how to calculate the effective memory address of an operand by using information held in registers and constants contained within a machine instruction or elsewhere.

TYPES OF ADDRESSING MODES

INHERENT OR IMPLIED MODE
No operand is explicitly specified in the instruction. Generally, some specific registers are assumed as the operand address and the destination of result.

IMMEDIATE ADDRESSING

In this mode of addressing the actual operand is contained as a part of the instruction itself. It is fast in processing because it does not involve fetching of operand address followed by the operand from the memory.

ABSOLUTE ADDRESSING

In this mode of addressing the memory address is included as the part of instruction itself .

INDIRECT MODE

In this mode of instruction the address of the operand in specified in the instruction rather than the instruction itself. Thus, this addressing mode is slow in operation but provides more flexibility for the manipulation of operand address.
REGISTER INDIRECT ADDRESSING

In this mode of addressing the registers containing the address of the memory location where the operand is stored is provided as a part of instruction. As a result , the instruction occupies less memory.

REGISTER ADDRESSING

In this mode addressing the registers containing the operand is provided as a part of instruction rather than the providing the address of the operand directly as it saves memory.

AUTOINCREMENT AND DECREMENT MODE

This addressing mode becomes effective when we need to deal with a series of records or a table. In this mode of addressing the address of the operand in the instruction is again and again incremented or decremented by one.

DIRECT ADDRESS MODE
In this mode the effective address is equal to the address part of the instruction. The operand resides in memory and its address is directly given by the address field of the instruction.

RELATIVE ADDRESSING
In this mode of addressing the content of the program counter is added to the address part of the instruction in order to obtain the effective part of the address.

INDEXED ADDRESSING
In this mode of addressing the content of the index register is added to the address part of the instruction to obtain the effective address.