What Are the Main Functions of a CPU?

Updated on October 19, 2015

The CPU, or Central Processing Unit, is both the heart and brains of every computer. Many of us do not know how important this unit is to the performance of a computer. How many of you have wondered about the basic functions of CPU? This article will answer that question, plus others including:

  • Why it is important to have a good cooling system to keep the CPU at the right temperatures.
  • Why it is so important to keep the CPU from overheating.

Common CPU Terms

What it Means or Does
Central Processing Unit, or the heart and brains of the computer.
Binary Code
A sequence of ones and zeros, or the language into which your CPU translates all data.
Arithmetical Logical Unit, responsible for all mathematical and logical operations
Program Counter
Tracks which instructions the CPU should execute next when processing data.
One hertz
The speed at which one operation is performed per second.
Multi-core processor
A CPU with two or more independent cores, so it can do more than one thing at once.

The Brains of the Computer

As I mentioned, the CPU is similar to human brain. Every single operation that you do with your computer is processed in the CPU. The performance of your computer is based upon simple mathematical operations and the CPU is the device that controls all of those operations.

Let's say we are using a calculator to add two numbers. You enter the numbers using your keyboard. The keyboard controller turns all of that information into binary code. Binary code consist of sequences of 0 and 1. This information is this sent to the registry and then transferred to the CPU. The CPU has an integrated ALU (Arithmetical Logical Unit). The ALU is responsible for all mathematical and logical operations.

Your request to add two numbers comes to the CPU and is transferred to the ALU. The ALU adds the binary numbers and returns the answer to the CPU, which transfers the answer to an output device.

Adding two numbers is a very simple example, but it illustrates the basic functions of the CPU. Every single step you perform on your computer is in one way or another connected to this central unit, so it is very important to keep your processor in good form. Overheating, especially, can lead your CPU to fail.

The Four Primary Functions of the CPU

The CPU processes instructions it receives in the process of decoding data. In processing this data, the CPU performs four basic steps:

  1. Fetch Each instruction is stored in memory and has its own address. The processor takes this address number from the program counter, which is responsible for tracking which instructions the CPU should execute next.
  2. Decode All programs to be executed are translated to into Assembly instructions. Assembly code must be decoded into binary instructions, which are understandable to your CPU. This step is called decoding.
  3. Execute While executing instructions the CPU can do one of three things: Do calculations with its ALU, move data from one memory location to another, or jump to a different address.
  4. Store The CPU must give feedback after executing an instruction and the output data is written to the memory.


The number of operations a CPU can perform depends upon its speed, which is measured in Hertz. One hertz is the speed during which one operation is performed in one second. Typically a computer's speed is measured in giga hertz. 1 GHz is the speed it takes the CPU to perform one million simple tasks. A "simple task" includes the smallest steps a processor can perform.

Usually the processor understands and performs assembly instructions that last four cycles. The faster your CPU, the more instructions it can perform in one second, but do not let this number fool you. The speed of the CPU is not the only metric that influences your computer's performance. There are many other factors, such as CPU architecture, cache size, and bus speed that must be evaluated to get independent results. Do not simply chase the highest speed when buying a processor. Evaluate all of the factors.

Multi-Core Processors

A multi-core processor is actually a CPU that had two or more independent cores. Cores are similar to usual processors. They execute program instructions. The main advantage of a multi-core processor is that it can run several instructions at the same tame. This feature increases performance speed significantly. All programs that have parallel computing features can run on musti-core processors.

How Can I Test a CPUs Performance?

CPU performance can be tested with various benchmarks and tools. These tools place a heavy workload on the CPU, but since a computer's overall performance involves several components—CPU, RAM, and video processor, among others—it is important to use testing benchmarks that evaluate all of these components at the same time.

These tools include like Sandra, which must be purchased, and Cinebench, which can be downloaded for free. Search for the best solution that fit your requirements and budget.


Submit a Comment

  • WestelCS profile image

    Tim Anthony 4 years ago

    This is really great information that even a beginner can easily understand. Knowledge of how the CPU works is essential for advanced techies. And, this hub will surely help beginners grasping more knowledge to become one.

  • Silwen profile image

    Silwen 5 years ago from Europe

    anjan, what do you mean by saying that you want more simple words?

  • profile image

    anjan 5 years ago

    I want more simple words.

  • Silwen profile image

    Silwen 5 years ago from Europe

    I have added some new interesting information, about CPU instruction cycle. All 4 steps that CPU makes are explained.

  • Silwen profile image

    Silwen 5 years ago from Europe

    Sakshi, you are welcome.

  • profile image

    Sakshi Bisen 5 years ago

    THANKS for given detailed information about CPU,it will help me to complete my project

  • profile image

    ranjani 5 years ago

    thanks for given detailed information about cpu it would me help in seminar to explain about cpu

  • Silwen profile image

    Silwen 6 years ago from Europe

    CPU stands for Central Processing Unit. Its functions are explained in the text above.

  • profile image

    sagir bello guga 6 years ago

    what is cpu

  • Silwen profile image

    Silwen 6 years ago from Europe

    You are welcome. I am glad, that you understood the main idea about CPU. Good luck in buying your new laptop. Apple products are known as one of the best products that can handle graphical (such as Photoshop) tasks. Off course there are many more good brands to be chosen from. I hope, that you will share your computer choice and your impressions.

  • Jamie Brock profile image

    Jamie Brock 6 years ago from Texas

    Thanks for explaining the CPU in understandable terms. I was just talking to my husband (IT guy) about it because I'm looking to buy a new laptop that has lots of memory and will handle Photoshop smoothly. He was telling me all about it but I still wasn't understanding. Thanks for sharing!

  • Silwen profile image

    Silwen 6 years ago from Europe

    Thank you, Ian. I am glad, that you found some useful information here.

  • Ian Dabasori Hetr profile image

    Ian D Hetri 6 years ago from Papua New Guinea

    I have read a bit CPU from here and there but this hub nailed it on the head. Its succinct and well written. Great hub. Voted up and useful