Pinterest Stumbleupon Whatsapp

Although most moderately tech-savvy people today know that a CPU is one of the components in their computers, not many people know what a CPU actually does. In fact, if asked, most people probably would not know what CPU stands for.

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?

First of all, what is a CPU?  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.

what is a cpu


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.


For this step, it’s important to know that no matter what code a program is written in, the compiler for that specific language breaks the code down to Assembly Language. 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, which the CPU can manipulate to execute the instructions it is given.


what is a cpu


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.

what is a cpu

Another important component of a CPU is called the “clock.” 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.

Thus, the CPU Clock speed refers to the number of times that a CPU’s clock cycles per second. Typical computers have a clock speed around 2.8 GHz (Gigahertz), which means that the clock cycles 2.8 billion times a second, and executes an equivalent number of instructions!

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.

In Part 2, I’ll explain more in depth about the technology that goes into dual- and quad-core technology, and what claims such as “Hyper-threading” mean. I’ll also  introduce the concept of overclocking a CPU (the practice of increasing the clock rate of a CPU to increase its performance and speed).

What CPU does your computer have? Have you ever thought about overclocking your computer? Let us know in the comments!

Leave a Reply

Your email address will not be published. Required fields are marked *

  1. Tawafgul
    September 26, 2016 at 12:25 pm

    Nothing cleared

  2. Ada
    September 7, 2016 at 2:32 pm

    I'm a senior over at NYU's School of Engineering. This article was a nice refresher. It gives you a quick gist of major topics covered in a computer architecture course.

  3. Dennis Primm
    July 14, 2015 at 5:48 pm

    Please forgive me... I meant to post my comment on the 7nm IBM Chip Doubles Performance, Proves Moore's Law Through 2018.

  4. Dennis Primm
    July 14, 2015 at 5:41 pm

    Thank you for this amazing article!!!

    When I got out of the Army I went to junior college to learn about electronics technology (my focus was on computers), we used the 6502 processor to train on and were looking forward to the Zilog Z80 coming onto the scene. We used machine code and assembler language to program the computer. That was back in the early 1980's. A lot of time has passed since then, but if my memory serves me correctly a CPU needs to have these three (3) items or building blocks:

    1) a Program Counter,
    2) an Instruction Register, and
    3) an Arithmetic Logic Unit (ALU)

    I haven't researched the latest CPUs and their building blocks, but those blocks were what was needed back in the old days. I would think the fundamentals are still the same today.

    If people really knew what goes on behind the scenes in their computers they would be quite amazed to know what is required to get what they are viewing on their monitors! There is quite a lot happening just to get the answer to a simple question like 1 + 1 = ? displayed on a seven segment display (like is used on a digital watch/clock) The answer of course is 2, but to arrive at that answer and display it in a seven segment display is quite an amazing process! You've got all of the basic logic gates (and, or, nor, exclusive or, and nand, nor, inverters, etc.) doing their thing to arrive at an answer and then once an answer is arrived at what is needed to display it is another feat. It really is quite an amazing concerted effort to perform just the basic arithmetic functions.

    I followed a link in this article about Quantum computers and that just amazes me too! I have a hard time understanding "qubits", but I'm sure in a few years they will be discussed about and understood just like we talk about "bits" (either a 0 or 1 state) today.

    I'm so glad you have shown us what the leading edge technology is. We need to have an appreciation of what it is and what it will do for us in the future.

    Thanks again for your article!

  5. eitrige
    May 13, 2015 at 9:51 am

    very interesting article, thank you!

  6. sankar
    March 19, 2015 at 9:28 am

    then go to school daily, definitely u'll get it one day.

    • kevin
      March 21, 2015 at 6:01 pm

      Its kinda hard to learn at school cuz right now I don't have the money to go to school every day

    February 25, 2015 at 9:13 am

    Woooooooow!! i've learn't alot from u people.thanx alot. but each and every function of the 4 primary functions takes place in different components of a CPU right? And if yes, then i would please luv to know the parts respectively.

  8. Lyth Hishmeh
    February 6, 2015 at 8:37 am

    You can at least appreciate the effort instead of being obnoxious pricks. At least she's making a contribution.

  9. aliya fatima
    December 13, 2014 at 5:36 pm

    bad post

  10. Alita
    March 31, 2010 at 10:48 am

    Nice article, thanks a lot!!!

  11. Jim Hamm
    March 30, 2010 at 2:10 pm

    Shouldn't that be 2.8 billion cycles, not 2.8 thousand? ....You stated: "2.8 GHz (Gigahertz), which means that the clock cycles two thousand eight hundred times a second"

  12. Simon
    March 30, 2010 at 8:25 am

    Yeah, 2.8 Gigahertz is 2.8 billion clock cycles per second.
    Not 2800, more like 2 800 000 000.

    • Angelina
      March 30, 2010 at 10:12 am

      That was a typo... I'll ask the editor to revise it. Thanks for pointing it out!

      • Abdullah Salem
        October 14, 2016 at 12:51 pm

        where is the second part of this article ?!

      • Zach
        February 9, 2017 at 1:08 am

        After reading this article i feel comfortable to go out and grab a laptop for myself,thank u so much bfl angelina :)
        Plz the sec part may god bless you.

  13. JustMe
    March 29, 2010 at 3:37 pm

    Wow, that's interesting.

    • Bello
      January 17, 2017 at 8:19 pm


  14. Brian Tkatch
    March 29, 2010 at 2:55 pm

    "Assembly language is a language that the CPU understands,"

    The CPU does not understand Assembly. It's understands op codes. An Assembler assembles the op code from the Assembly code.

    "binary code"

    I think you mean op codes. Which are in binary. But then again, all code is ultimately binary.

    "Using its Arithmetic Logic Unit (ALU), the CPU can calculate extremely complicated mathematical functions"

    Not really. The CPU does simple functions. A library usually breaks down complex functions into simple ones for the CPU.

    There are many other things the CPU does, such as handle interrupts, redirect instructions, and whatnot.

    I look forward to part 2.