Registers In Computer Architecture

Register is a fast temporary memory of a computer that is used to store, and transfer data and instructions that are being used by the CPU. Registers are also known as CPU registers. A CPU register may contain a storage address, an instruction or data. Let explain the most common registers in computer Architecture.

Registers in Computer Architecture || When the size of Memory is 4096 x 16 Words.

Here the 4096 are the total number of words/locations in the main memory and 16 represent the size of each word/location. To represent 4096 memory locations, 12 bits are required. And there are 16 bits in each word.  So, 16  bits are required to represent the actual word in memory. We can calculate required bits through the following formula,

  • No. of bits required for address = Bits required for total memory locations
  • No. of bits required for Word = Size of each word in Bits

Therefore in 4096 x 16 Words memory, 12 bits will require for address and 16 bits will require for any word. Word is a block of data.

Conclusion: The size of all data registers will be the same because all data registers will contain the same size of data i.e. DR, AC, IR, and TR. And the same case for address registers, all address registers will carry the same address. Address registers include PC and AR.

If the size of memory is 4096 x 16 Words then a list of most common registers with its specifications are given below in the image

Registers in Computer Organization

A table form above diagram shows the following

Register Symbol Number of bits Function
Data register DR 16 Holds data as a memory operand
Accumulator AC  16 Processor register to hold data
Instruction register IR 16 Holds instruction code
Temporary register TR 16 Holds temporary data
Address register AR 12 Holds address for the memory
Program counter PC 12 Holds the address of next instruction
Input register INPR 8 holds input character
Output register OUTR 8 holds output character

The input and output register has no concern with the size of the main memory. Input register receives data from input devices i.e. keyboard, mouse, and output register sends data to output devices i.e. monitors, printers, etc. This incoming data from input devices or outgoing data to output devices may be 8-bits, 16-bits, or more at a time.

 When to Calculate the Memory size (Register and WORD size is given)

If the size of an address register is given i.e. 24-bits then no. of memory locations will be 224. And if size of Word is 8-bytes (64bits) then Size of memory can calculate as

Size of memory = Total no. of locations x word size

                        = 224 x 26 bits = 230 bits = 1GB



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