bit

Acronym for binary digiT and the unit of measurement for variety , uncertainty , statistical entropy and information , all of which are quantified in terms of the (average) number of binary digits required to count a given number of alternatives (see degree of freedom ). Equivalent interpretations of this unit are the average number of decisions required to exhaust a given number of alternatives, the average number of relays needed to represent a certain number, the average number of answers to yes-no questions necessary to select one out of a given number of objects. Thus the answer to a yes-or-no question conveys one bit of information. Two distinctions create four alternatives and not knowing which is desirable measures two bits of uncertainty. A Hollerith card with 12-by-80 places, each of which may be punched or left solid, can store 960 bits of information. More generally, n equally likely alternatives correspond to log_2 n bits (see law of requisite variety ). (krippendorff )