The bit (a portmanteau of binary digit)[1] is a basic unit of
information used in computing and digital communications. A binary
digit can have only one of two values, and may be physically
represented with a two-state device. These state values are most
commonly represented as either a 0or1.
The two values of a binary digit 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 information
entropy of a binary random variable that is 0 or 1 with equal
probability,[2] or the information that is gained when the value of
such a variable becomes known.[3][4]
Confusion often arises because the words bit and binary digit are used
interchangeably. But, within information theory, a bit and a binary
digit are fundamentally different types of entities. A binary digit is
a number that can adopt one of two possible values (0 or 1), whereas a
bit is the maximum amount of information that can be conveyed by a
binary digit. By analogy, a binary digit is like a container, whereas
information is the amount of matter in the container.
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 binary digit is either simply bit (recommended by the
IEC 80000-13:2008 standard) or lowercase b (recommended by the IEEE
1541-2002 and
Contents 1 History 2 Physical representation 2.1 Transmission and processing 2.2 Storage 3 Unit and symbol 3.1 Multiple bits 4
History[edit]
The encoding of data by discrete bits was used in the punched cards
invented by
Multiples of bits v t e Decimal Value SI 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 Binary Value IEC JEDEC 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 - See also Nibble Byte Orders of magnitude of data Multiple bits[edit]
Multiple bits may be expressed and represented in several ways. For
convenience of representing commonly reoccurring groups of bits in
information technology, several units of information have
traditionally been used. The most common is the unit byte, coined by
Integer (computer science)
Primitive data type
Trit (Trinary digit)
Bitstream
Entropy (information theory)
References[edit] ^ Mackenzie, Charles E. (1980). Coded Character Sets, History and
Development. The Systems Programming Series (1 ed.). Addison-Wesley
Publishing Company, Inc. p. x. ISBN 0-201-14460-3.
LCCN 77-90165. Archived from the original on 18 November 2016.
Retrieved 22 May 2016. [1]
^ John B. Anderson, Rolf Johnnesson (2006) Understanding Information
Transmission.
^ Simon Haykin (2006), Digital Communications
^ IEEE Std 260.1-2004
^ "Units: B". Archived from the original on 4 May 2016.
^ a b Norman Abramson (1963),
External links[edit] Look up bit in Wiktionary, the free dictionary.
v t e Units of information Base unit bit Platform-dependent units nibble byte syllable parcel word Platform-independent units unibit (1) dibit (2) tribit (3) quadbit (4) quartet (4) sextet (6) octet (8) hextet (16) declet (10) doublet (16) quadlet (32) octlet (64) hexlet (128) triad (3) tetrad (4) pentad (5) hexad (6) heptad (7) octad (8) slab (12) catena (24) Traditional bit units kilobit megabit gigabit terabit petabit exabit zettabit yottabit Traditional byte units kilobyte megabyte gigabyte terabyte petabyte exabyte zettabyte yottabyte IEC bit units kibibit mebibit gibibit tebibit pebibit exbibit zebibit yobibit IEC byte units kibibyte mebibyte gibibyte tebibyte pebibyte exbibyte zebibyte yobibyte v t e Data types Uninterpreted Bit
Byte
Trit
Tryte
Word
Numeric Arbitrary-precision or bignum Complex Decimal Fixed point Floating point Double precision Extended precision Half precision Long double Minifloat Octuple precision Quadruple precision Single precision Integer signedness Interval Rational Pointer Address physical virtual Reference Text Character String null-terminated Composite Algebraic data type generalized Array Associative array Class Dependent Equality Inductive List Object metaobject Option type Product Record Set Union tagged Other Boolean Bottom type Collection Enumerated type Exception Function type Opaque data type Recursive data type Semaphore Stream Top type Type class Unit type Void Related topics Abstract data type Data structure Generic Kind metaclass Parametric polymorphism Primitive data type Protocol interface Subtyping Type constructor Type conversion Type system Type theory See also platform-dependent and independent units of |