# Bit

## Unit of information / From Wikipedia, the free encyclopedia

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The **bit** is the most basic unit of information in computing and digital communications. The name is a portmanteau of **binary digit**.^{[1]} The bit represents a logical state with one of two possible values. These values are most commonly represented as either "1" or "0", but other representations such as *true*/*false*, *yes*/*no*, *on*/*off*, or *+*/*−* are also widely used.

The relation between these values and the physical states of the underlying storage or device is a matter of convention, and different assignments may be used even within the same device or program. It may be physically implemented with a two-state device.

A contiguous group of binary digits is commonly called a *bit string*, a bit vector, or a single-dimensional (or multi-dimensional) *bit array*.
A group of eight bits is called one *byte*, but historically the size of the byte is not strictly defined.^{[2]} Frequently, half, full, double and quadruple words consist of a number of bytes which is a low power of two. A string of four bits is usually a *nibble*.

In information theory, one bit is the information entropy of a random binary variable that is 0 or 1 with equal probability,^{[3]} or the information that is gained when the value of such a variable becomes known.^{[4]}^{[5]} As a unit of information, the bit is also known as a *shannon*,^{[6]} named after Claude E. Shannon.

The symbol for the binary digit is either "bit", per the IEC 80000-13:2008 standard, or the lowercase character "b", per the IEEE 1541-2002 standard. Use of the latter may create confusion with the capital "B" which is the international standard symbol for the byte.