All the data stored in computer - every word, picture, number and sound - is captured as a series of electrical pulses that are either on or off. A number system called binary is used to represent these pulses with "1" meaning "on" and "0" meaning "off".
A single binary digit, known as a "bit", switches a single switch on or off. By linking together these switches, the computer can carry out the complex operations we demand.
Bits and bytes
1 bit = a binary digit either 1 (on) or 0 (off).
1 byte = 8 bits
1 kilobyte =