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:

“The Christian always swears a bloody oath that he will never do it again. The civilized man simply resolves to be a *bit* more careful next time.”

—H.L. (Henry Lewis)

“A slight digression: that *bit* about my mother was a deliberate lie. In reality, she was a woman of the people, simple and coarse, sordidly dressed in a kind of blouse hanging loose at the waist. I could, of course, have crossed it out, but I purposely leave it there as a sample of one of my essential traits: my light-hearted, inspired lying.”

—Vladimir Nabokov (1899–1977)

“The public, with its mob yearning to be instructed, edified and pulled by the nose, demands certainties; it must be told definitely and a *bit* raucously that this is true and that is false. But there are no certainties.”

—H.L. (Henry Lewis)