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.

Fetch

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.

Decode

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.

Execute

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.

Writeback

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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