In the register addressing mode, the operands exist in those registers that reside within a CPU. In this case, we select a specific register from a certain register field in the given instruction. The k-bit field is capable of determining one 2k register.
In this article, we will take a look at the Register Addressing Mode according to the GATE Syllabus for CSE (Computer Science Engineering). Continue reading ahead to learn more.
Table of Contents
Register Addressing Mode
All the instructions include operands. These operands could be a processor register, a memory location, or an I/O device. Here, the instructions that use the processor’s register to represent the operands refer to the instructions that are in the register addressing mode.
The effective address here refers to the register in which the value of an operand is present. Here:
EA = R
To represent register addressing mode, here are two instructions below as examples:
Add X4, X3
Load X3, X2
You can see that in the given example, the Add instruction makes use of the registers to represent both the operands. In a similar way, the Load instruction also makes use of the registers to represent both the given operands. Thus, the instruction given above makes use of register addressing mode in order to describe the operand’s address. The figure below shows the Add instruction that is used in the example given earlier.
Pros
In the case of register addressing mode, no memory references exist since the value that is to be operated here is present in the given register.
Cons
The registers enclose a limited address space. Thus, it has a fixed limit on the overall size of the value that can be stored in it.
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