In the case of relative addressing mode, we need to add a constant to the content of the register in order to refer to the address of the next operand. But in some computers, the program counter is used instead of using a register.
In this article, we will take a look at the Relative Addressing Mode according to the GATE Syllabus for CSE (Computer Science Engineering). Continue reading ahead to learn more.
Table of Content
Relative Addressing Mode
In the case of relative addressing mode, the Effective Address or EA of the operand gets calculated when we add the content of the CPU register along with the instruction word’s address part. Thus, the effective address could be calculated here if we add the displacement (the immediate value that is given in the instruction) along with the register value. Here, the given instruction’s address part is a signed number (usually), either negative or positive. The effective address calculated in this case is relative to the next instruction’s address.
EA = Displacement + CPU Register
Here is a symbolic representation of the relative address mode:
X(PC)
Here is how the effective address for it:
EA = X + (PC)
Since the operand addresses here are found relative to a program counter, it is known as the relative address mode.
Classification
We can classify the Relative Addressing Mode into three of the following types:
- Program Counter or PC Relative Addressing Mode.
- Base Register Addressing Mode.
- Indexed Addressing Mode or Index Register Relative Addressing Mode.
Advantage
The relative addressing mode doesn’t require memory references.
Disadvantage
The relative addressing mode doesn’t have any disadvantages as such.
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