Processor of a Computer : CPU

We all know that computer has a CPU. It stands for Central Processing Unit. In general ‘CPU’ refers to a microprocessor which is a control unit of computer. Processor is an electronics device system that processes the instructions of computer programs running on a computer. A computer program contains instructions like arithmetic, logical, control or any Input/output operations which is processed by the Processor.

The first commercially used Microprocessor was Intel 4040 which was introduced on 1970. Now we are mostly using Processors of Intel and AMD, Intel i7 is the latest processor of Intel and Zen series are the latest processors made by AMD.

What is multi-core processor?

Modern CPU is of multiple cores. We have heard terms like Dual core processor, Quad core or Octa core processor. Multi-core processor is actually a physical unit that contains more than one individual processor. So Daul core processor contains two processors and similarly Quad core contains four and octa core contains 8 processors.

Multi-Core enables hardware threading. Means if one processor is executing one program then another new program which is started by user does not have to wait for the completion of currently executing program, because another processor of multi-core CPU will be allotted to execute second program. This way the execution and operation speed of a computer is increases and a computer can do more task in less time.

Operations of CPU

The fundamental operations a processor do are same among all processors irrespective of their version, cost or the different technologies they are using. It executes programs and a program is nothing but a set of instructions or commands. Processors process the instructions in three steps. Those are fetch, decode and execute.

1.Fetch: The  instructions written in a program is in a state of numbers or a sequence of numbers present in program memory called program counter(PC). PC stores addresses/locations of all the instructions set in a sequence. In first step CPU fetch instruction by determining the address defined by PC. After fetching the first instruction, PC(The memory address) increments by the length of the fetched instruction so that it will point to the next instruction. This way CPU fetch all the instructions of a program one by one.

2.Decode: There is a circuitry called instruction decoder in every processor. It converts the instructions to electric signal that is send to other circuitry of CPU for further operations.

3.Execute : After fetch and decode, execute step is performed. This may be a single process or multiple, all parts of CPU is connected with each other to perform the required operation.

Structure of a CPU


Control Unit-  This unit communicates with both arithmetic logic unit, Memory unit as well as the input and output devices. It does not execute any program instructions, but it starts other unit of a CPU by providing required electric signals to execute instruction set of a program.

Registers Unit:  It hold instructions during the execution of a program. It stores and supply operands to the ALU during the execution of an operation.

Combinational logic unit: This unit is a combination of all the logical unit like Arithmetic Logic Unit(ALU), Floating-point Unit (FPU) etc. ALU performs the Integer arithmetic and bitwise logic operations and FPU performs all the mathematical operations on floating point variables.

Memory management Unit: This unit converts logically memory addresses to physical RAM addresses. It also acts as virtual memory when required for any CPU operation.


Why speed of a processor is measured by Hertz?

Generally speed means the distance covered in unit time, that is meter per second or Kilometer per hour. But in case of Processor we don’t use such type of units, rather we use Hertz as the unit to measure the speed of a processor. But how this hertz which is a unit of frequency is applicable for measuring the speed of a processor ??

So basically processor executes the instructions. Then obviously the speed of a processor should be determined by the number of instructions one processor can execute in unit time. Now we should understand that CPU is a digital circuit, so it executes instructions by producing sequential signals in it and that signals stimulate other unit to process the instructions. This sequential signal is nothing but the clock signal (Generally a digital square wave) generated by the oscillator circuit of CPU. The frequency of this square wave pulses determine the rate at which CPU can execute instructions. If the clock pulses will come out frequently or if the frequency of the pulse will be higher, then the instructions a CPU can execute per second will also be more. So the speed of a Processor is measured by the frequency it can produce.


Thank You for visiting.


  1. Nikhi August 27, 2017
    • Subhasmita Mohapatra August 27, 2017

Add Comment