A bit field is a common idiom used in computer programming to store multiple, logical, neighboring bits, where each of the sets of bits, and single bits can be addressed. A bit field is most commonly used to represent integral types of known, fixed bit-width. A well-known usage of bit-fields is to represent a set of bits, and/or series of bits, known as flags. For example, the first bit in a bit field can be used to determine the state of a particular attribute associated with the bit field.
A bit field is distinguished from a bit array in that the latter is used to store a large set of bits indexed by integers and is often wider than any integral type supported by the language. Bit fields, on the other hand, typically fit within a machine word, and the denotation of bits is independent of their numerical index.