bit, in communication and information theory, a unit of information equivalent to the result of a choice between only two possible alternatives, as between 1 and 0 in the binary number system generally used in digital computers. The term is shortened from the words “binary digit.” It is also applied to a unit of computer memory corresponding to the ability to store the result of a choice between two alternatives, in which 1 is a high voltage and 0 is a low voltage.