How Computers really work ?

We know, the main part of computer is the CPU. But how does CPU does all the work physically ? Lets learn about it. All Processors mainly consists of TRANSISTORS. A transistor is like a switch in a circuit. I suggest you to read the  complete post without skipping so that you will understand better.

A transistor looks like this :

The transistor is made up of a Semiconductor(Green base in the image), such as Silicon. There is some gap between the yellow places and the current will not flow in between these two areas, unless a metal(Grey in image) is placed above it and wrapped with an insulator. When some current passes through the Input ( shown in image above ), unless the gate is also charged, the current will not pass to the Output. For better understanding, follow these GIFs :




When the Current passes through gate, it makes the current flow between the INPUT and OUTPUT, thus letting the current pass through the transistor. Its like a switch, but to on the switch , we need to pass the current through gate. And here comes the binary into play.

In binary numbering system, there are only 2(0,1) digits unlike the decimal system which has 10 digits(0-9).

"1" in binary means on, and "0" means off. So, if we pass the current through gate of transistor, it means "1" and sending no current means "0". Since there are only two options, On or Off, we are using binary, which has only 0 and 1.

Now, by using two of these transistors, we can make some LOGIC GATES.

Logic gates are the main parts of any kind of integrated circuits. All the integrated circuits contain logic gates. The logical arrangement of these transistors give us different kinds of gates. We will discuss about one Logic gate, the "OR" logic gate .

The OR GATE:

If we think of transistors as switches, and make a circuit like the above diagram, we made an OR gate. Turning on any of the two switches, i.e., Passing current through any of Gates of the two transistors will make the bulb glow. 

So, we can say this:

These 1s and 0s means, sending and not-sending current into the Gates of the transistors.

1 in output means, the bulb is glowing, and 0 in output means bulb is not glowing.

Similarly, There are many other logic gates. Here are their Inputs and outputs :

Now, we have covered all the Logic Gates. A Wise arrangement of these logic gates is what makes Integrated circuits. A CPU of a modern computer, by which you are reading this blog, consists of nearly A BILLION TRANSISTORS which makes up many of these logic gates, thus helping to do calculations and reading instructions faster . As the distance between the INPUT & OUTPUT of the transistor decrease, it helps to fit more and more transistors on a small CPU. According to Moore's law, every 18 months, the number of transistors on the CPU doubles.

A modern CPU has transistors , which are very very small i.e., the length between input and output of the transistors is nearly 10-20 nanometers = 0.0000001 cm .

Here is an image of the SCOTT cpu:

And thats how the core of the CPU is structured. Thank you. :)

Credits for the GIFs: InOneLesson