bit

(b)

   1. the basic unit of the amount of data. Each bit records one of the two possible answers to a single question: "0" or "1," "yes" or "no," "on" or "off." When data is represented as binary (base-2) numbers, each binary digit is a single bit. In fact, the word "bit" was coined by the American statistician and computer scientist John Tukey (b. 1915) in 1946 as an acronym for binary digit. Somewhat more generally, the bit is used as a logarithmic unit of data storage capacity, equal to the base-2 logarithm of the number of possible states of the storage device or location. For example, if a storage location stores one letter, then it has 26 possible states, and its storage capacity is log² 26 = 4.7004 bits.

   2. a unit of information content, now known also as the shannon. In information and communications theory, if a message has probability p of being received, then its information content is -log² p shannons. This unit is often called the bit, because if the message is a bit string and all strings are equally likely to be received, then the information content is equal the number of bits.