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What are the Registers in Computers Organization?

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What are Registers in Computers Organization?

The register is high-speed memory CPU registers are used by the CPU.Early store data intermediate results during processing. Registers are the fastest type of memory used by the CPU, even faster than level 1 cache. generally, data register in at one time the faster the CPU. register size usually matches and so it is for either 32 bits 64 bits today.Some especially registers are longer most CPU.
students register for the high-speed memory locations into the microprocessor.
CPU uses these locations to store the data and instructions temporarily for processing.
CPU process, store and transfer the data from one component to another with the help of registers for processing.

The number of Registers varies among computers.

It increases the processing power of CPU.

Each register receives information holds it temporarily and pass it on as directed by CU.

The size of Register depends on Computer Architecture.

There are different types of Registers.

  1. Program Counter(PC).

  2. Instruction Register(IR).

  3. Memory Address Register(MAR).

  4. Memory Buffer Register(MBR).

  5. Instruction Pointer Register(IPR).

  6. Stack Pointer Register(SPR).

  7. General Purpose Registers(A,B,C,D).

  8. Index Register(DI,SI).

  9. Segment Register(CS,DS,SS,ES).

Program Counter:-

Holds Address of next instruction to be fetched and executed.

Instruction Pointer

Hold the current instruction that is being executed.


Holds the address of active memory location.


Holds the contents of memory location read from and written into the memory.


The arrangement of data is called stack and data is stored in or retrieved from the stack using LIFO(last in first out).


Holds the instruction address of Registers.

General Purpose Registers:-

These Registers are used to perform arithmetic and logical operations.AX,BX,CX,DX are 2 byte registers.

The general data registers are AX, BX, CX, DX. These four registers are all 16-bit registers. Each register can be divided into high and low 8-bit registers. For example, AX can be divided into two 8-bit registers AH and AL.

i. Accumulator Registers:-used for arithmetic and logical operation.

ii. Base Register:- used for indirect addressing.

iii. Counter Register:- used for counting purpose.

iv. Data Register:- used for division and multiplication.

Index Register:-used for the data segment and modifying operand address.

There are two types of index registers.

i. SI(Souse Index).

ii. DI(Destination Index).

Segment Register:-group of 4 Registers CS,DS,SS,ES. These registers are 2 bytes.

The 8086 also has four 16-bit segment registers, which are CS, DS, SS, and ES. Four 16-bit segment registers and four address pointer registers generate 20-bit addresses for memory addressing.

CS(Code Segment):- Holds the base location of all executable instructions in the program.

DS(Data Segment):- default base location for the memory location.

SS(Stack Segment):-contain the base location for memory variables.

ES(Extra Segment):- additional base location for the memory location.

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