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Monday, 16 June 2014


How does a CPU work: Processing and working of a Processor Explained

CPU or the Central Processing Unit is a vital and key component of the desktop, laptop, tablet or even the smartphone that you are using to read this article right now!
I know that many of you are real tech savvy people and have a lot of interest in computing but many of you are blank when it comes to how a CPU works as a matter of fact the full form of the abbreviation is seldom known to many.
But when searching for a new desktop or laptop, and typical CPU-related terms such as “quad-core” or ” i7 core”  pop out from advertisements, each proclaiming their superiority over the other — what is a person to do, especially if he or she has no idea what either of those terms mean?
Not to worry in this article today I'll explain the basic functioning of a CPU and fill you all up with some cool facts in due course.

The Basics

First of all, what is a CPU? As mentioned earlier, CPU (also commonly called a microprocessor) stands for “central processing unit”. It’s a very suitable name, because it describes exactly what the CPU does: it processes instructions that it gathers from decoding the code in programs and other such files. A CPU has four primary functions: fetch, decode, execute, and writeback.


In the first step, the CPU retrieves the instruction that it needs to run from program memory. Each instruction in a program (which contains millions of instructions) is stored at a specific address. The CPU has a program counter, which keeps track of the CPU’s position in the program more specifically, the address of the instruction that the CPU is accessing.


All of you are familiar with the fact that programs are written in different programming languages like java, c/c++ etc and is compiled by a compiler for execution by converting any language in its input to assembly language as an output. Assembly language is a language that the CPU understands, but may vary between different CPUs. From there on, an "assembler" translates Assembly Language into binary code (that is in the form of 0 and one), which the CPU can manipulate to execute the instructions it is given.


Based on the instructions it is given, the CPU can then do one of three things:
1) Using its Arithmetic Logic Unit (ALU), the CPU can calculate extremely complicated mathematical functions.
2) Move data from one memory location to another.
3) Jump to different addresses in the program based on decisions made by the CPU itself.
The diagram above shows the setup of an extremely simple microprocessor capable of performing these actions.


Typically, each of the actions taken by the CPU produces some sort of output. The CPU takes this output and writes it into the computer’s memory. For example, if a program wanted to execute the first item of the list above on two operands, 3 and 5, the output, 8, would be written back into a specific address. However, for the 3rd bullet, the program counter (which, as stated above, is used to keep track of the CPU’s progress through a program) simply changes to reflect the start of the next set of instructions.
When these four steps have been completed, the Program Counter moves onto the next instruction and repeats the entire process again, until the termination of the program.

The Clock

Another important component of a CPU is called the “clock.” I know that all the Electronics or Electrical Engineering students or professionals are familiar with this term but still I'll explain. The clock produces a signal that acts to synchronize the logic units within the CPU as they execute the instructions given in a program. In the diagram above, the purple line represents the signal of a clock as it is being inputted into a logic unit. For every time the line goes from low to high, and back to low (one cycle), an instruction is carried out.
Now you understand that those figures in Gigahertz written on the processor packaging means and refer to its clock speed ie the number of times that a CPU’s clock cycles per second.
A 3.7Ghz processor means that its clock cycles 3.7 billion times in one second, and executes an equivalent number of instructions! So go ahead and flaunt this knowledge with your friends.
Now, even though this seems like an incredible amount of information processed, a CPU operating solely on the technology explained above would still be slow, if it were not for parallelism, and multi-core technology. But I’ll leave that for later, as I’ve just given you a great deal of information to digest. Now, you’re a little closer to learning how processors work, and to to gauging which processor is best for your needs.
If you still can't decide then as always I'm there to help you out anytime.
Do leave a comment or suggestion in the comment box regarding this article.....

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  1. Hey thank a lot for writing an article on such basic concept. Really helped me in making my son's school project.

    1. Happy to know that I could be of some assistance to you ma'am.
      I always try to keep my articles in the simplest language possible so that they are easy to understand.
      Thank you for visiting.

  2. Hey Vishvesh Can you please tell which will be the best buy of a 1TB PC Hard Drive under 4K & please suggest which RAM i should buy for a Dual Core Pentium Machine ....

    1. You have three options all from reputed and trusted brands:
      Adata HV620 2.5 inch 1 TB
      WD My Passport Ultra 2.5 inch 1 TB
      Dell Backup Plus 1TB USB 3.0

      RAM module depends on your requirements mainly processor comes secondary. Which OS you use, whats the nature of your work and whats your budget play a crucial role. If you answer these question then I'll be able to help you better.
      Still just a random suggestion you can buy the Kingston HyperX Blu DDR3 2 GB PC RAM.
      Feel free to ask any further questions.

  3. The mentioned Hard Drives are quite good as external/portable drive. But the fact is i am looking for an INTERNAL HARD DISK under the budget of 4000..If possible then plz suggest me a good 2GB DDR3 RAM under 2500..Basically i use my PC to play mid range games like Far Cry1-2, IGI & GTA SERIES (EXCEPT GTA 5), HD MOVIES & runs some apps like MS OFFICE 10, PHOTOSHOP, nd of course net surfing.. Mostly i use win 8 OS..

    1. Sorry for the miscommunication, I'll give you two options pick anyone of then in accordance with your budget and availability.
      WD Blue WD10EZEX 1 TB
      Seagate Barracuda 1 TB
      Both have 64MB cache memory and 7200RPM rate and are from reputed brands.

      For your processor I'll suggest that you go for G.Skill NT DDR3 2 GB (1 x 2 GB) PC RAM with upto 1333Mhz clock speed.
      It will give you more than enough speed for the specified tasks.

  4. Thanks for your suggestion..!! I think my PC has an INTEL G41 Graphic Chiset, so my question is will it (G.Skill NT DDR3) support with my pc config ..??

    1. No it won't as its a DDR2 ram compatible motherboard so you should get yourself a transcend 2gb Jm800 qlu 2g it's a 800mhz ram n will suffice your needs easily