A computer file can be considered as a sequence of zeroes and ones. Each one or zero is known as a bit. Representing a file in ones and zeroes is known as binary format.
1000000100000000000000000000000000010111000001100000000000000000
It is convenient to organise the bits into groups of eight. Each group of eight bits is known as a byte. This file is eight bytes long.
10000001 00000000 00000000 00000000 00010111 00000110 00000000 00000000