Binary digit

1000 103 kbit kilobit 10002 106 Mbit megabit 10003 109 Gbit gigabit 10004 1012 Tbit terabit 10005 1015 Pbit petabit 10006 1018 Ebit exabit 10007 1021 Zbit zettabit 10008 1024 Ybit yottabit	1024 210 Kibit kibibit Kbit kilobit 10242 220 Mibit mebibit Mbit megabit 10243 230 Gibit gibibit Gbit gigabit 10244 240 Tibit tebibit - 10245 250 Pibit pebibit - 10246 260 Eibit exbibit - 10247 270 Zibit zebibit - 10248 280 Yibit yobibit -

The bit is a basic unit of information in computing and digital communications. A bit can have only one of two values, and may therefore be physically implemented with a two-state device. These values are most commonly represented as either a 0or1. The term bit is a portmanteau of binary digit. In information theory, the bit is equivalent to the unit shannon, named after Claude Shannon.

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 (near/far, night/day, cat/dog, ...). 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 classical (i.e., non-quantum) bit values.

The symbol for bit, as a unit of information, is either simply bit (recommended by the IEC 80000-13:2008 standard) or lowercase b (recommended by the IEEE 1541-2002 standard). A group of eight bits is commonly called one byte, but historically the size of the byte is not strictly defined.

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