bits

Bits are the fundamental unit of information in information theory and digital computing. A bit represents one of two possible states, typically 0 or 1. The term bit is a contraction of binary digit and was coined by John Tukey in the late 1940s. In information theory, a single bit denotes the amount of information required to distinguish between two equally likely alternatives.

In practical terms, bits quantify data size and transfer rates. Data storage and communication are measured in bits or multiples such as kilobits, megabits, and gigabits. Data rates are commonly described in bits per second (bps). Hardware and software describe processing capacity and data paths in terms of how many bits are moved or processed per operation, and eight bits form a byte, a more common unit for expressing memory size and file lengths.

The physical realization of a bit relies on binary states of a system, such as voltage levels in electronics or magnetic orientations in storage media. Because information content depends on probability, the theoretical framework behind bits uses logarithms (base 2), with a bit representing the information gained when reducing uncertainty by half in the case of two equiprobable outcomes. While eight bits equal one byte in standard usage, prefixes for data quantity can reflect decimal or binary bases, leading to differences in advertised versus actual storage capacity in some contexts.