If computer use Binary number so why you use binary to hexa decimal or binary to octal?

Answer 1

You don't use binary because it's very hard reading a bunch of zeros and ones.

You use hexa because each hexa digit corresponds to 4 bits, this makes it very easy to convert from hexa do binary and vice versa.

For a similar reason you use octal because each digit corresponds to 3 binary digits.

Example:

0101 10102

Has 8 binary digits so it will be 2 hexa digits:

01012 = 516 , 10102 = A16

So the full number will be:

0101 10102 = 5A16

This works for hexa and octal because 16 and 8 are powers of 2, it would also work for 4, 32, 64 or any other ower of 2 . Since 10 for decimal notation is not a power of 2 converting from binary is not so direct.