A bit, short for binary digit, is the smallest unit of data in computing and can have one of two values: zero or one. Physically, each bit may be stored or sent as two distinct states such as different voltage levels, opposing magnetisation directions or varying light intensities, much like a switch being on or off. Computers and networks work entirely in bits, using sequences of them to represent every type of information. Input devices such as keyboards, mice or voice-activated receivers translate human actions into streams of bits for processing, while output devices such as screens, speakers and printers convert those bit patterns back into images, sounds or text we can understand.
Groups of eight bits form a byte, which underpins coding systems like the American Standard Code for Information Interchange (ASCII). In ASCII each letter, number or symbol is assigned a unique eight-bit pattern, for example the capital letter A is 01000001, the digit 9 is 00111001 and the symbol # is 00100011. By arranging bytes in different ways, computers can store and transmit text, graphics, photographs, voice recordings, video and music, all as patterns of bits.