bit

The bit is a basic unit of information in information theory, computing, and digital communications. The name is a portmanteau of binary digit.In information theory, one bit is typically defined as the information entropy 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. As a unit of information, the bit is also known as a shannon, named after Claude E. Shannon.
As a binary digit, the bit represents a logical state, having only one of two values. It may be physically implemented with a two-state device. These values are most commonly represented as either 0or1, but other representations such as true/false, yes/no, +/−, or on/off are common. 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 symbol for the binary digit is either bit per recommendation by the IEC 80000-13:2008 standard, or the lowercase character b, as recommended by the IEEE 1541-2002 and IEEE Std 260.1-2004 standards. A group of eight binary digits is commonly called one byte, but historically the size of the byte is not strictly defined.

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