A **bit** (a contraction of **binary digit**) is the basic capacity of information in computing and telecommunications; a bit can have the value of either 1 or 0 (one or zero) only. These attributes may be implemented, in a variety of systems, by means of a two state device.

In computing, a bit can be defined as a variable or computed quantity that can have only two possible values. These two values are often interpreted as binary digits and are usually denoted by the numerical digits 0 and 1. The two values can also be interpreted as logical values (*true*/*false*, *yes*/*no*), algebraic signs (*+*/*−*), activation states (*on*/*off*), or any other two-valued attribute. The correspondence 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. The length of a binary number may be referred to as its "bit-length".

In information theory, one bit is typically defined as the uncertainty of a binary random variable that is 0 or 1 with equal probability, or the information that is gained when the value of such a variable becomes known.

In quantum computing, a *quantum bit* or *qubit* is a quantum system that can exist in superposition of two bit values, "true" and "false".

The symbol for bit, as a unit of information, is either simply "bit" (recommended by the ISO/IEC standard 80000-13 (2008)) or lowercase "b" (recommended by the IEEE 1541 Standard (2002)).

Read more about Bit: History, Representation, Information Capacity and Information Compression, Multiple Bits, Bit-based Computing, Other Information Units

### Famous quotes containing the word bit:

“Take a decayed Christian ... and the remains of a Stoic; mix thoroughly with good manners, a *bit* of money and an old-fashioned education; simmer for several years in a university. Result: a scholar and a gentleman. Well, there were worse types of human being.”

—Aldous Huxley (1894–1963)

“Sadie: How’d you get him here? He was out stiff.

Jack: Hair of the dog that *bit* him.

Sadie: Hair? He must have swallowed the dog.”

—Robert Rossen (1908–1966)

“I have given my pain a name and call it “dog”Mit is every *bit* as faithful, every *bit* as nosey and shameless, every *bit* as entertaining, every *bit* as clever as any other dog—and I can boss it around and vent my bad moods on it, just as others do with their dogs, servants, and wives.”

—Friedrich Nietzsche (1844–1900)