The word bit began as a shorthand scribbled in a 1947 Bell Labs memo
Every photo, song and message you own boils down to bits, choices between just two states. The name itself was coined when statistician John Tukey squashed binary digit into three letters in a memo on 9 January 1947, and Claude Shannon made it famous a year later.
A bit holds one of two values, most often written 1 and 0, though true and false or on and off work just as well. Which physical state counts as which is pure convention, and can even differ inside a single device. Four bits make a nibble and eight a byte, although historically the byte's size was not fixed. In information theory, a bit is the uncertainty in a fair coin-like choice, or what you learn when the answer is revealed; in that role it is also called a shannon.
Ralph Hartley proposed measuring information logarithmically in 1928. Shannon's landmark 1948 paper, A Mathematical Theory of Communication, first put the word bit into print and credited Tukey. Compression tries to express data in fewer bits, while error correction deliberately adds spare bits so mistakes can be caught and fixed; algorithmic information theory asks how short a string's description can possibly get.
Binary storage is far older than computers. Punched cards were invented by Basile Bouchon and Jean-Baptiste Falcon in 1732 and refined by Joseph Marie Jacquard in 1804, later taken up by Charles Babbage, Herman Hollerith and IBM. Each hole position was either punched or not: one bit. Morse code in 1844 and teleprinters from 1870 also encoded text digitally. Early electrical logic, in lift controls, telephone exchanges and Konrad Zuse's computer, stored bits as open or closed relays.
From the 1940s, engineers tried stranger media: pressure pulses in mercury delay lines, charges on the face of a cathode ray tube, dots printed on glass. Magnetic cores, tapes, drums and disks took over in the 1950s and 1960s, and magnetised stripes survive on metro tickets and some credit cards. Today a bit may be a charge level in a memory capacitor, a microscopic pit on an optical disc, or a black or white square in a QR code. Standards bodies still disagree on the symbol: bit or a lowercase b, easily confused with B for byte.
Source: Bit
