Difference between direct addressing mode and indirect addressing mode in detail?

Answer 1

Direct addressing mode means the operand address is contained in the instruction. In the 8085, an example is LDA 1234H, which loads the accumulator with the contents of memory location 1234H. In the 8086/8088, an example is MOV AL,[1234H], which accomplishes nearly the same thing.

Indirect addressing mode means the operand address is contained in a register. In the 8085, an example is LDAX B, which loads the accumulator with the contents of the memory location specified in register BC. In the 8086/8088, an example is MOV AL,[BX], which accomplishes nearly the same thing.

Answer 2

Direct addressing mode means the operand address is contained in the instruction. In the 8085, an example is LDA 1234H, which loads the accumulator with the contents of memory location 1234H. In the 8086/8088, an example is MOV AL,[1234H], which accomplishes nearly the same thing. (AL instead of A)

Indirect addressing mode means the operand address is contained in a register. In the 8085, an example is LDAX B, which loads the accumulator with the contents of the memory location specified in register BC. In the 8086/8088, an example is MOV AL,[BX], which accomplishes nearly the same thing. (AL instead of A, and BX instead of BC)

Answer 3

Immediate addressing mode:- in this mode data is in register, and the operand is actually present in the instruction direct in memory. It can be used to define and use constants initial values.

• operand is part of instruction

• operand = address field, e.g. ADD 5

• ADD 5 to contents of accumulator

• 5 is operand

• no memory reference to fetch data, fast, limited range.

Direct addessing mode:- In this mode all work is done in RAM, it is in main memory processor registers are used as temprory storages location where the data in a register are accessed using the register mode.

• EA = A

• Address field contains address of operand

• Effective address (EA) = address field (A) e.g. ADD A

• Add contents of cell A to accumulator

• look in memory at address A for operand

• single memory reference to access data, No additional calculations to work out effective address, Limited address space

Answer 4

The difference between direct and indirect addressing is with direct addressing, the actual address of the operand is used. With indirect addressing a memory word is used.

Answer 5

When the address part specfies the address of an operand, the instruction is said to have direct address.

Indirect address:When designate an address of a memory word.