Question

Why computer only understand binary number?

Answer 1

why computer can understand only binary language?

That's a nice question. To understand why computers use Binary; you'll first have to understand that binary language is basically just two digits - 0 and 1. Each of these digits actually represent 'state'; let's call it 'On' and 'Off'. To understand this better in electronics; an 'on' state could be thought of as a positive voltage say '5V' and 0 would represent '0' volts. These are the two states the electronic devices can understand.

Now, the data can be represented using a series of these on and off stages. That is we can represent the information through the series of on and off states in electronics. 

So visualize it as follows: The circuits themselves don't understand anything except that they can be in the on state or off states. A series of on and off signals can be used to represent data - and that's why computers understand binary code. 

I'd like more inputs from the electronics and computer science engineers. I'm not sure whether I can explain this in even simpler words.