# Bit

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)).

### 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)