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:

“Scarlett O’Hara: Oh, oh, Rhett. For the first time I’m finding out what it is to be sorry for something I’ve done.

Rhett Butler: Dry your eyes. If you had it all to do over again, you’d do no differently. You’re like the thief who isn’t the least *bit* sorry he stole, but he’s terribly, terribly sorry he’s going to jail.”

—Sidney Howard (1891–1939)

“This dog and man at first were friends;

But when a pique began,

The dog, to gain some private ends,

Went mad and *bit* the man.”

—Oliver Goldsmith (1730?–1774)

“I well recall my horror when I heard for the first time, of a journalist who had laid in a pair of what were then called bicycle pants and taken to golf; it was as if I had encountered a studhorse with his hair done up in frizzes, and pink bowknots peeking out of them. It seemed, in some vague way, ignominious, and even a *bit* indelicate.”

—H.L. (Henry Lewis)