Binary Digit

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The bit is the most basic unit of information in computing and digital communication. The name is a portmanteau of binary digit. Its symbol is either "bit" (IEC standard) or lowercase "b" (IEEE standard). Use of the latter may create confusion with capital "B", which is the international standard symbol for the byte. The bit represents a logical state with one of two possible values. These values are most commonly represented as 1 and 0, but other representations such as true/false, yes/no, on/off, and +/− 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. 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, or the information that is gained when the value of such a variable becomes known. As a unit of information, the bit is also known as a shannon, named after Claude E. Shannon. As a measure of the length of a digital string that is encoded as symbols over a binary alphabet (i.e. Σ = { 0 , 1 } {\displaystyle \Sigma =\{{\texttt {0}},{\texttt {1}}\}} ), the bit has been called a binit, but this usage is now rare.