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The bit is a
basic unit
basic unit
of information in
computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithm of an algorithm (Euclid's algorithm) for calculating the greatest common divisor (g.c.d ...

computing
and digital
communication Communication (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of th ...

communication
s. The name is a
portmanteau A portmanteau (, ) or portmanteau word (from "portmanteau (luggage) A portmanteau is a piece of luggage Baggage or luggage consists of bags, cases, and containers which hold a travel Travel is the movement of people between distant ...

portmanteau
of binary digit. The bit represents a logical state with one of two possible
values In ethics Ethics or moral philosophy is a branch of philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about Metaphysics, existence, reason, Epistemology, knowledge, Ethics, values, Philosophy ...
. These values are most commonly represented as either , 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. It may be physically implemented with a two-state device. The symbol for the binary digit is either ''bit'' per recommendation by the
IEC 80000-13 ISO 80000 or IEC 80000 is an international standard An international standard is a technical standard A technical standard is an established norm (social), norm or requirement for a repeatable technical task which is applied to a common and repeate ...
:2008 standard, or the lowercase character ''b'', as recommended by the
IEEE 1541-2002 IEEE 1541-2002 is a standard issued in 2002 by the Institute of Electrical and Electronics Engineers The Institute of Electrical and Electronics Engineers (IEEE) is a professional association for electronic engineering and electrical engineerin ...
and
IEEE Std 260.1-2004 IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a professional association A professional association (also called a professional body, professional organization, or professional society) seeks to advocacy, further a pa ...
standards. A contiguous group of binary digits is commonly called a
bit string A bit array (also known as bit map, bit set, bit string, or bit vector) is an array data structure that compactly stores bits. It can be used to implement a simple set data structure. A bit array is effective at exploiting bit-level parallelism in ...
, a bit vector, or a single-dimensional (or multi-dimensional)
bit array A bit array (also known as bit map, bit set, bit string, or bit vector) is an array data structure In computer science, an array data structure, or simply an array, is a data structure consisting of a collection of ''elements'' (value (compute ...
. A group of eight binary digits is called one 
byte The byte is a unit of digital information that most commonly consists of eight bit The bit is a basic unit of information in computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It ...
, 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. In
information theory Information theory is the scientific study of the quantification (science), quantification, computer data storage, storage, and telecommunication, communication of Digital data, digital information. The field was fundamentally established by the ...
, one bit is the
information entropy In information theory, the entropy of a random variable is the average level of "information", "surprise", or "uncertainty" inherent in the variable's possible outcomes. The concept of information entropy was introduced by Claude Shannon in hi ...
of a
binary Binary may refer to: Science and technology Mathematics * Binary number In mathematics and digital electronics, a binary number is a number expressed in the base-2 numeral system or binary numeral system, which uses only two symbols: ty ...
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 In computing and telecommunications, a unit of information is the capacity of some standard data storage system or communication channel, used to measure the capacities of other systems and channels. In information theory, units of information are ...
, the bit is also known as a '' shannon'', named after Claude E. Shannon.


History

The encoding of data by discrete bits was used in the
punched card A punched card (also punch cardSteven Pinker, in ''The Stuff of Thought'', Viking, 2007, p.362, notes the loss of ''-ed'' in pronunciation ''as it did in ice cream, mincemeat, and box set, formerly iced cream, minced meat, and boxed set.'' or pu ...

punched card
s invented by
Basile Bouchon Basile Bouchon was a textile A textile is a flexible material made by creating an interlocking network of yarns or thread (yarn), threads, which are produced by spinning (textiles), spinning raw fibres (from either natural or synthetic sour ...
and Jean-Baptiste Falcon (1732), developed by
Joseph Marie Jacquard Joseph Marie Charles ''dit'' (called or nicknamed) Jacquard (; 7 July 1752 – 7 August 1834) was a French weaver and merchant. He played an important role in the development of the earliest programmable loom (the " Jacquard loom"), which in turn ...

Joseph Marie Jacquard
(1804), and later adopted by
Semyon Korsakov Semyon Nikolaevich Korsakov (russian: Семён Николаевич Корсаков, ) (January 14, 1787 – December 1, 1853 OS) was a Russia Russia (russian: link=no, Россия, , ), or the Russian Federation, is a country spann ...
,
Charles Babbage Charles Babbage (; 26 December 1791 – 18 October 1871) was an English polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans a subs ...

Charles Babbage
,
Hermann Hollerith Herman Hollerith (February 29, 1860 – November 17, 1929) was an American businessman, inventor, and statistician who developed an electromechanical tabulating machine The tabulating machine was an electromechanical machine designed to assist ...
, and early computer manufacturers like
IBM International Business Machines Corporation (IBM) is an American multinational technology company headquartered in Armonk, New York, with operations in over 170 countries. The company began in 1911, founded in Endicott, New York, as the C ...

IBM
. A variant of that idea was the perforated
paper tape Five- and eight-hole punched paper tape file:Harwell-dekatron-witch-10.jpg, Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop Punched tape or perforated pape ...

paper tape
. In all those systems, the medium (card or tape) conceptually carried an array of hole positions; each position could be either punched through or not, thus carrying one bit of information. The encoding of text by bits was also used in
Morse code Morse code is a method used in telecommunication Telecommunication is the transmission of information by various types of technologies over wire A wire is a single usually cylindrical A cylinder (from Greek Greek may refer to: ...
(1844) and early digital communications machines such as teletypes and
stock ticker machine Ticker tape was the earliest electrical dedicated financial communications medium, transmitting stock Stock (also capital stock) is all of the shares into which ownership of a corporation A corporation is an organization—usually a ...
s (1870).
Ralph Hartley Ralph Vinton Lyon Hartley (November 30, 1888 – May 1, 1970) was an American electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matte ...
suggested the use of a logarithmic measure of information in 1928. Claude E. Shannon first used the word "bit" in his seminal 1948 paper "
A Mathematical Theory of Communication "A Mathematical Theory of Communication" is an article by mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Greek: ) includes the study of such topics as numbers ( and ), formulas ...
". He attributed its origin to John W. Tukey, who had written a Bell Labs memo on 9 January 1947 in which he contracted "binary information digit" to simply "bit".
Vannevar Bush Vannevar Bush ( ; March 11, 1890 – June 28, 1974) was an American engineer, inventor and science administrator, who during World War II, World War II headed the U.S. Office of Scientific Research and Development (OSRD), through which almo ...

Vannevar Bush
had written in 1936 of "bits of information" that could be stored on the
punched card A punched card (also punch cardSteven Pinker, in ''The Stuff of Thought'', Viking, 2007, p.362, notes the loss of ''-ed'' in pronunciation ''as it did in ice cream, mincemeat, and box set, formerly iced cream, minced meat, and boxed set.'' or pu ...

punched card
s used in the mechanical computers of that time. The first programmable computer, built by
Konrad Zuse Konrad Zuse (; 22 June 1910 – 18 December 1995) was a German civil engineer A civil engineer is a person who practices civil engineering Civil engineering is a Regulation and licensure in engineering, professional engineering discipli ...

Konrad Zuse
, used binary notation for numbers.


Physical Representation

A bit can be stored by a digital device or other physical system that exists in either of two possible distinct
states State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper in Columbia, South Carolina, Un ...
. These may be the two stable states of a flip-flop, two positions of an
electrical switch In electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics The field of electronics is a branch of p ...

electrical switch
, two distinct
voltage Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential The electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is the ...

voltage
or
current Currents or The Current may refer to: Science and technology * Current (fluid) A current in a fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or external force. ...
levels allowed by a
circuitCircuit may refer to: Science and technology Electrical engineering * Electrical circuit, a complete electrical network with a closed-loop giving a return path for current ** Analog circuit, uses continuous signal levels ** Balanced circuit, p ...

circuit
, two distinct levels of , two directions of
magnetization In classical electromagnetism Classical electromagnetism or classical electrodynamics is a branch of theoretical physics Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and s ...

magnetization
or
polarization Polarization or polarisation may refer to: In the physical sciences *Polarization (waves), the ability of waves to oscillate in more than one direction, in particular polarization of light, responsible for example for the glare-reducing effect of ...
, the orientation of reversible double stranded
DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral gro ...

DNA
, etc. Bits can be implemented in several forms. In most modern computing devices, a bit is usually represented by an
electrical Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position In physics, motion is the phenomenon in which an object changes its positio ...

electrical
voltage Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential The electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is the ...

voltage
or
current Currents or The Current may refer to: Science and technology * Current (fluid) A current in a fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or external force. ...
pulse, or by the electrical state of a flip-flop circuit. For devices using positive logic, a digit value of 1 (or a logical value of true) is represented by a more positive voltage relative to the representation of 0. The specific voltages are different for different logic families and variations are permitted to allow for component aging and noise immunity. For example, in
transistor–transistor logic Transistor–transistor logic (TTL) is a logic family In computer engineering Computer engineering (CoE or CpE) is a branch of engineering Engineering is the use of scientific method, scientific principles to design and build machine ...
(TTL) and compatible circuits, digit values 0 and 1 at the output of a device are represented by no higher than 0.4 volts and no lower than 2.6 volts, respectively; while TTL inputs are specified to recognize 0.8 volts or below as 0 and 2.2 volts or above as 1.


Transmission and processing

Bits are transmitted one at a time in serial transmission, and by a multiple number of bits in
parallel transmission 300px, Parallel versus serial communication In data transmission Data transmission and data reception (or, more broadly, data communication or digital communications) is the transfer and reception of data (a Digital data, digital bitstream or a d ...
. A
bitwise operation In computer programming, a bitwise operation operates on a bit string, a bit array or a Binary numeral system, binary numeral (considered as a bit string) at the level of its individual bits. It is a fast and simple action, basic to the higher le ...
optionally processes bits one at a time. Data transfer rates are usually measured in decimal SI multiples of the unit bit per second (bit/s), such as kbit/s.


Storage

In the earliest non-electronic information processing devices, such as Jacquard's loom or Babbage's
Analytical Engine The Analytical Engine was a proposed mechanical general-purpose computer designed by English mathematician and computer pioneer Charles Babbage. It was first described in 1837 as the successor to Babbage's difference engine, which was a des ...
, a bit was often stored as the position of a mechanical lever or gear, or the presence or absence of a hole at a specific point of a or . The first electrical devices for discrete logic (such as
elevator An elevator (North American English North American English (NAmE, NAE) is the most generalized variety (linguistics), variety of the English language as spoken in the United States and Canada. Because of their related histories and ...

elevator
and
traffic light Traffic lights, traffic signals, stoplights or robots (as they are known in South Africa) are signalling devices positioned at road intersections, pedestrian crossing A pedestrian crossing (primarily British English) or crosswalk (primar ...

traffic light
control circuits,
telephone switches manually connecting calls with cord pairs at a telephone switchboard A telephone exchange, telephone switch, or central office is a telecommunications Telecommunication is the transmission of information Information can be thought of as ...
, and Konrad Zuse's computer) represented bits as the states of electrical relays which could be either "open" or "closed". When relays were replaced by
vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. The type kn ...
s, starting in the 1940s, computer builders experimented with a variety of storage methods, such as pressure pulses traveling down a mercury delay line, charges stored on the inside surface of a
cathode-ray tube A cathode-ray tube (CRT) is a vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current An electric current is a stream of charged particles, such as electrons ...
, or opaque spots printed on glass discs by
photolithographic Photolithography, also called optical lithography or UV lithography, is a process used in microfabrication to pattern parts on a thin film or the bulk of a substrate (also called a Wafer (electronics), wafer). It uses light to transfer a geometry, ...
techniques. In the 1950s and 1960s, these methods were largely supplanted by
magnetic storage Magnetic storage or magnetic recording is the storage of data Data (; ) are individual facts A fact is something that is truth, true. The usual test for a statement of fact is verifiability—that is whether it can be demonstrated t ...
devices such as
magnetic core memory Magnetic-core memory was the predominant form of random-access Random access (more precisely and more generally called direct access) is the ability to access an arbitrary element of a sequence in equal time or any datum from a population of ...
,
magnetic tape Magnetic tape is a medium for , made of a thin, magnetizable coating on a long, narrow strip of . It was developed in Germany in 1928, based on . Devices that record and playback audio and video using magnetic tape are s and s respectively. A ...

magnetic tape
s,
drums The drum is a member of the percussion A percussion instrument is a musical instrument A musical instrument is a device created or adapted to make Music, musical sounds. In principle, any object that produces sound can be consid ...
, and disks, where a bit was represented by the polarity of
magnetization In classical electromagnetism Classical electromagnetism or classical electrodynamics is a branch of theoretical physics Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and s ...

magnetization
of a certain area of a
ferromagnetic Ferromagnetism is the basic mechanism by which certain materials (such as iron Iron () is a with Fe (from la, ) and 26. It is a that belongs to the and of the . It is, on , right in front of (32.1% and 30.1%, respectively), formi ...
film, or by a change in polarity from one direction to the other. The same principle was later used in the magnetic bubble memory developed in the 1980s, and is still found in various
magnetic strip A magnetic stripe card is a type of card capable of storing data by modifying the magnetism Magnetism is a class of physical phenomena that are mediated by magnetic field A magnetic field is a vector field that describes the magnetic infl ...
items such as
metro Metro, short for metropolitan, may refer to: Geography * Metro (city), a city in Indonesia * A metropolitan area A metropolitan area or metro is a region consisting of a densely populated core city, urban core and its less-populated surro ...
tickets and some
credit card #REDIRECT Credit card #REDIRECT Credit card A credit card is a payment card issued to users (cardholders) to enable the cardholder to pay a merchant for goods and services based on the cardholder's promise to the card issuer to pay them for ...

credit card
s. In modern
semiconductor memory Semiconductor memory is a used for , such as . It typically refers to MOS memory, where data is stored within (MOS) on a memory chip. There are numerous different types using different semiconductor technologies. The two main types of (RA ...
, such as
dynamic random-access memory Dynamic random-access memory (dynamic RAM or DRAM) is a type of random-access memory, random-access semiconductor memory that stores each bit of data in a memory cell (computing), memory cell, usually consisting of a tiny capacitor and a tr ...
, the two values of a bit may be represented by two levels of
electric charge Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respectively). Like c ...
stored in a
capacitor A capacitor is a device that stores electric charge in an electric field An electric field (sometimes E-field) is the physical field that surrounds electrically-charged particle In physics Physics (from grc, φυσική (ἐπ ...

capacitor
. In certain types of
programmable logic array PLA schematic example A programmable logic array (PLA) is a kind of programmable logic device used to implement combinational logic electrical network, circuits. The PLA has a set of programmable AND gate planes, which link to a set of programma ...
s and
read-only memory Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing sof ...
, a bit may be represented by the presence or absence of a conducting path at a certain point of a circuit. In
optical disc In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithm of an algorithm (Euclid's algorithm) for calculating the greatest ...
s, a bit is encoded as the presence or absence of a microscopic pit on a reflective surface. In one-dimensional
bar code A barcode or bar code is a method of representing data in a visual, machine-readable form. Initially, barcodes represented data by varying the widths and spacings of parallel lines. These barcodes, now commonly referred to as linear or one-dimen ...
s, bits are encoded as the thickness of alternating black and white lines.


Unit and symbol

The bit is not defined in the
International System of Units The International System of Units, known by the international abbreviation SI in all languages and sometimes Pleonasm#Acronyms_and_initialisms, pleonastically as the SI system, is the modern form of the metric system and the world's most wi ...
(SI). However, the
International Electrotechnical Commission The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization A standards organization, standards body, standards developing organization (SDO), or s ...
issued standard
IEC 60027 IEC 60027 (formerly IEC 27) is a for s published by the , comprising the following parts: * IEC 60027-1: General * IEC 60027-2: Telecommunications and electronics * IEC 60027-3: Logarithmic and related quantities, and their units * IEC 60027-4: Sy ...
, which specifies that the symbol for binary digit should be ''bit'', and this should be used in all multiples, such as ''kbit'', for kilobit. However, the lower-case letter b is widely used as well and was recommended by the IEEE 1541 Standard (2002). In contrast, the upper case letter B is the standard and customary symbol for byte.


Multiple bits

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 In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithm of an algorithm (Euclid's algorithm) for calculating the greatest commo ...

units of information
have traditionally been used. The most common is the unit
byte The byte is a unit of digital information that most commonly consists of eight bit The bit is a basic unit of information in computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It ...
, coined by
Werner Buchholz Werner Buchholz (24 October 1922 – 11 July 2019) was a German-American computer scientist. After growing up in Europe, Buchholz moved to Canada and then to the United States. He worked for International Business Machines International Busi ...
in June 1956, which historically was used to represent the group of bits used to encode a single
character Character(s) may refer to: Arts, entertainment, and media Literature * ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk * ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to Theophrastus M ...
of text (until
UTF-8 UTF-8 is a variable-width character encoding Character encoding is the process of assigning numbers to Graphics, graphical character (computing), characters, especially the written characters of Language, human language, allowing them to be ...
multibyte encoding took over) in a computer and for this reason it was used as the basic addressable element in many
computer architecture In computer engineering, computer architecture is a set of rules and methods that describe the functionality, organization, and implementation of computer systems. The architecture of a system refers to its structure in terms of separately specifi ...
s. The trend in hardware design converged on the most common implementation of using eight bits per byte, as it is widely used today. However, because of the ambiguity of relying on the underlying hardware design, the unit
octet Octet may refer to: Music * Octet (music) In music, an octet is a musical ensemble consisting of eight Musical instrument, instruments or voices, or a musical composition written for such an ensemble. Octets in classical music Octets in Europea ...
was defined to explicitly denote a sequence of eight bits. Computers usually manipulate bits in groups of a fixed size, conventionally named "
words In linguistics Linguistics is the scientific study of language A language is a structured system of communication used by humans, including speech (spoken language), gestures (Signed language, sign language) and writing. Most lang ...
". Like the byte, the number of bits in a word also varies with the hardware design, and is typically between 8 and 80 bits, or even more in some specialized computers. In the 21st century, retail personal or server computers have a word size of 32 or 64 bits. The
International System of Units The International System of Units, known by the international abbreviation SI in all languages and sometimes Pleonasm#Acronyms_and_initialisms, pleonastically as the SI system, is the modern form of the metric system and the world's most wi ...
defines a series of decimal prefixes for multiples of standardized units which are commonly also used with the bit and the byte. The prefixes
kilo KILO (94.3 FM, 94.3 KILO) is a radio station broadcasting in Colorado Springs The City of Colorado Springs is the List of cities and towns in Colorado#Home rule municipality, Home Rule Municipality that is the county seat and the List of ci ...
(103) through
yotta Yotta is the largest decimal The decimal numeral system A numeral system (or system of numeration) is a writing system A writing system is a method of visually representing verbal communication Communication (from Latin ''commu ...
(1024) increment by multiples of 1000, and the corresponding units are the
kilobit The kilobit is a multiple of the unit bit The bit is a basic unit of information in computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation o ...
(kbit) through the yottabit (Ybit).


Information capacity and information compression

When the information capacity of a storage system or a communication channel is presented in ''bits'' or ''bits per second'', this often refers to binary digits, which is a computer hardware capacity to store binary data (0 or 1, up or down, current or not, etc.). Information capacity of a storage system is only an upper bound to the quantity of information stored therein. If the two possible values of one bit of storage are not equally likely, that bit of storage contains less than one bit of information. If the value is completely predictable, then the reading of that value provides no information at all (zero entropic bits, because no resolution of uncertainty occurs and therefore no information is available). If a computer file that uses ''n'' bits of storage contains only ''m'' < ''n'' bits of information, then that information can in principle be encoded in about ''m'' bits, at least on the average. This principle is the basis of lossless data compression, data compression technology. Using an analogy, the hardware binary digits refer to the amount of storage space available (like the number of buckets available to store things), and the information content the filling, which comes in different levels of granularity (fine or coarse, that is, compressed or uncompressed information). When the granularity is finer—when information is more compressed—the same bucket can hold more. For example, it is estimated that the combined technological capacity of the world to store information provides 1,300 exabytes of hardware digits. However, when this storage space is filled and the corresponding content is optimally compressed, this only represents 295 exabytes of information. When optimally compressed, the resulting carrying capacity approaches Shannon information or
information entropy In information theory, the entropy of a random variable is the average level of "information", "surprise", or "uncertainty" inherent in the variable's possible outcomes. The concept of information entropy was introduced by Claude Shannon in hi ...
.


Bit-based computing

Certain bitwise operation, bitwise computer central processing unit, processor instructions (such as ''bit set'') operate at the level of manipulating bits rather than manipulating data interpreted as an aggregate of bits. In the 1980s, when bitmapped computer displays became popular, some computers provided specialized bitblt, bit block transfer instructions to set or copy the bits that corresponded to a given rectangular area on the screen. In most computers and programming languages, when a bit within a group of bits, such as a byte or word, is referred to, it is usually specified by a number from 0 upwards corresponding to its position within the byte or word. However, 0 can refer to either the most significant bit, most or least significant bit depending on the context.


Other information units

Similar to torque and energy in physics; Information#Information theory, information-theoretic information and data storage size have the same Dimensional analysis, dimensionality of Unit of measurement, units of measurement, but there is in general no meaning to adding, subtracting or otherwise combining the units mathematically. Other units of information, sometimes used in information theory, include the ''natural digit'' also called a ''nat (unit), nat'' or ''nit (unit of information), nit'' and defined as logarithm, log2 ''e'' (≈ 1.443) bits, where ''e'' is the e (mathematical constant), base of the natural logarithms; and the ''dit (unit), dit'', ''ban (unit), ban'', or ''hartley (unit), hartley'', defined as log2 10 (≈ 3.322) bits. This value, slightly less than 10/3, may be understood because 103 = 1000 ≈ 1024 = 210: three decimal digits are slightly less information than ten binary digits, so one decimal digit is slightly less than 10/3 binary digits. Conversely, one bit of information corresponds to about natural logarithm, ln 2 (≈ 0.693) nats, or log10 2 (≈ 0.301) hartleys. As with the inverse ratio, this value, approximately 3/10, but slightly more, corresponds to the fact that 210 = 1024 ~ 1000 = 103: ten binary digits are slightly more information than three decimal digits, so one binary digit is slightly more than 3/10 decimal digits. Some authors also define a binit as an arbitrary information unit equivalent to some fixed but unspecified number of bits.


See also

* Byte * Integer (computer science) * Primitive data type * Trit (computing), Trit (Trinary digit) * Qubit (quantum bit) * Bitstream * Entropy (information theory) * Baud, Baud rate (bits per second) * Binary numeral system * Ternary numeral system * Shannon (unit)


References


External links


Bit Calculator
– a tool providing conversions between bit, byte, kilobit, kilobyte, megabit, megabyte, gigabit, gigabyte
BitXByteConverter
– a tool for computing file sizes, storage capacity, and digital information in various units {{Data types Binary arithmetic Primitive types Data types Units of information