Difference between Direct and Immediate Addressing Modes
Prerequisite – Addressing Modes
1. Direct Addressing Mode: In direct addressing mode, the address field contains the address of the operand.
Effective Address (EA) = address field of operand
Example: Add the contents of register 1303 to the accumulator.
Only a single memory reference is required to access data. So no additional calculations are required to work out the effective address.
2. Immediate Addressing Mode: In immediate addressing mode, the operand is a part of the instruction.
Here the Operand = Address Field
Example: Add 3 to the accumulator.
No memory reference is required to fetch data. So no additional calculations are required to work out the effective address. It is a fast method. But the downside is that it has a limited range. Now let’s compare Direct and Immediate addressing modes.
|S. No.||Parameters||Direct Addressing Mode||Immediate Addressing Mode|
|1.||Address Field||Address fields contain the effective address of the operand.||There is no address field as an operand is a part of the instruction. In place of address field, immediate addressing mode has operand field.|
|2.||Memory Referencing||It requires one reference to memory.||It does not require any reference to memory.|
|3.||Process Speed||It is slower compared to the immediate mode.||It is faster compared to the direct addressing mode.|
|4.||Range||It has more range than in immediate mode.||It has a limited range.|
|5.||Example||Add (1303)||ADD 3|
|6.||Advantage||Easy as direct reference to memory||There is no memory reference for fetching data.|
|7.||Disadvantage||Restricted address space||Constrained operand magnitude|
|8.||Application||It assists in accessing static data and implementing variables.||Set the register to a constant value.|
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