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In computing and telecommunications a bit is a basic unit of information storage and communication; it is the maximum amount of information that can be stored by a device or other physical system that can normally exist in only two distinct states. These states are often interpreted (especially in the storage of numerical data) as the binary digits 0 and 1. They may be interpreted also as logical values, either "true" or "false"; or two settings of a flag or switch, either "on" or "off".
In information theory, "one bit" is typically defined as the uncertainty of a binary random variable that is 0 or 1 with equal probability,^{[1]} or the information that is gained when the value of such a variable becomes known.^{[2]}
In quantum computing, a quantum bit or qubit is a quantum system that can exist in superposition of two bit values, "true" and "false".
The symbol for bit, as a unit of information, is "bit" or (lowercase) "b"; the latter being recommended by the IEEE 1541 Standard (2002).
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The encoding of data by discrete bits was used in the punched cards invented by Basile Bouchon and JeanBaptiste Falcon (1725), developed by Joseph Marie Jacquard (1804), and later adopted by Semen Korsakov, Charles Babbage, Hermann Hollerith, and early computer manufacturers like IBM. Another variant of that idea was the perforated 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 potentially carrying one bit of information. The encoding of text by bits was also used in Morse code (1844) and early digital communications machines such as teletypes and stock ticker machines (1870).
Ralph Hartley suggested the use of a logarithmic measure of information in 1928.^{[3]} Claude E. Shannon first used the word bit in his seminal 1948 paper A Mathematical Theory of Communication. He attributed its origin to John W. Tukey, who had written a Bell Labs memo on 9 January 1947 in which he contracted "binary digit" to simply "bit". Interestingly, Vannevar Bush had written in 1936 of "bits of information" that could be stored on the punch cards used in the mechanical computers of that time. ^{[4]} The first programmable computer built by Konrad Zuse used binary notation for numbers, whose bits were realized as electrical relays which could be either "open" or "closed".
Bits can be implemented in many forms. In most modern computing devices, a bit is usually represented by an electrical voltage or current pulse, or by the electrical state of a flipflop circuit. For devices using positive logic, a digit value of 1 (true value or high) is represented by a positive voltage relative to the electrical ground voltage (up to 5 volts in the case of TTL designs), while a digit value of 0 (false value or low) is represented by 0 volts.
In semiconductor memory, such as dynamic randomaccess memory or flash memory, the two values of a bit may be represented by two levels of electrical charge stored in a capacitor. In programmable logic arrays and certain types of readonly memory, a bit may be respresented by the presence or absence of a conducting path at a certain point of a circuit. In magnetic storage devices such as magnetic tape, magnetic disc, or magnetic bubble memory, it may be represented by the polarity of magnetization of a certain area of a ferromagnetic film. In optical discs, a bit is encoded as the presence or absence of a microscopic pit on a reflective surface.
Information capacity of a storage system is only an upper bound to the actual quantity of information stored therein. If the two possible values of one bit of storage are not equally likely, that bit of storage will contain less than one bit of information. Indeed, if the value is completely predictable, then the reading of that value will provide no information at all (zero bits). 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 data compression technology. Sometimes the name bit is used when discussing data storage while shannon is used for the statistical bit.^{[citation needed]}
There are several units of information which are defined as multiples of bits, such as byte (8 bits), kilobit (either 1000 or 2^{10} = 1024 bits), megabyte (either 8,000,000 or 8×2^{20} = 8,388,608 bits), etc.
Computers usually manipulate bits in groups of a fixed size, conventinally named "words". The number of bits in a word varies with the computer model; typically between 8 to 80 bits; or even more in some specialized machines.
The International Electrotechnical Commission's standard IEC 60027 specifies that the symbol for bit should be "bit", and this should used in all multiples, such as "kbit" (for kilobit).^{[5]} However, the letter "b" (in lower case) is widely used too. The letter "B" (upper case) is both the standard and customary symbol for byte.
In telecommunications (including computer networks), data transfer rates are usually measured in bits per second (bit/s) or its multiples, such as kbit/s. (This unit is not to be confused with baud.)
When a bit within a group of bits such as a byte or word is to be referred to, it is usually specified by a number from 0 (not 1) upwards corresponding to its position within the byte or word. However, 0 can refer to either the most significant bit or to the least significant bit depending on the context, so the convention of use must be known.
Certain bitwise computer processor instructions (such as bit set) operate at the level of manipulating bits rather than manipulating data interpreted as an aggregate of bits.
Other units of information, sometimes used in information theory, include the natural digit also called a nat or nit and defined as log_{2} e (≈ 1.443) bits, where e is the base of the natural logarithms; and the decit, ban or Hartley, defined as log_{2}10 (≈ 3.322) bits.^{[3]}. Conversely, one bit of information corresponds to about ln 2 (≈ 0.693) nats, or log_{10} 2 (≈ 0.301) Hartleys. Some authors also define a binit as an arbitrary information unit equivalent to some fixed but unspecified number of bits.)^{[6]}


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From Old English bita and bite  all from ProtoGermanic *biton, from ProtoIndoEuropean *bheid (“‘to split’”).
Singular 
Plural 
bit (plural bits)




bit (not comparable)
Positive 
Superlative 
See bite
bit
Coined by John Tukey in 1946 as an abbreviation of binary digit, probably influenced by connotations of “small portion”.[1][2] First used in print 1948 by Claude Shannon. Compare byte and nybble.
Singular 
Plural 
bit (plural bits)


Borrowed from English bit < binary digit.
bit m.
singular  plural  

nominative  bit  bity 
genitive  bitu  bitů 
dative  bitu  bitům 
accusative  bit  bity 
vocative  bite  bity 
locative  bitu  bitech 
instrumental  bitem  bity 
bit n.
From English beat
bit
From bȉti (“‘to be’”)
bȋt m. (Cyrillic spelling би̑т)
singular  plural  

nominative  bȋt  biti 
genitive  biti  bítī 
dative  biti  bitima 
accusative  bit  biti 
vocative  biti  biti 
locative  biti  bitima 
instrumental  biti  bitima 
bȉt m. (Cyrillic spelling би̏т)
singular  plural  

nominative  bȉt  bìtovi 
genitive  bita  bitova 
dative  bitu  bitovima 
accusative  bit  bitove 
vocative  bite  bitovi 
locative  bitu  bitovima 
instrumental  bitom  bitovima 
bit m. (plural bits)
Singular 
Plural 
Inflection for bit  Singular  Plural  

common  Indefinite  Definite  Indefinite  Definite 
Base form  bit  biten  bitar  bitarna 
Possessive form  bits  bitens  bitars  bitarnas 
bit
From English bit < binary digit.
Inflection for bit  Singular  Plural  

common  Indefinite  Definite  Indefinite  Definite 
Base form  bit  biten  bitar  bitarna 
Possessive form  bits  bitens  bitars  bitarnas 
bit
bit
bit
bit
nominative  singular  plural 

benim (my)  bitim  bitlerim 
senin (your)  bitin  bitlerin 
onun (his/her/its)  biti  bitleri 
bizim (our)  bitimiz  bitlerimiz 
sizin (your)  bitiniz  bitleriniz 
onların (their)  bitleri  bitleri 
accusative  singular  plural 

benim (my)  bitimi  bitlerimi 
senin (your)  bitini  bitlerini 
onun (his/her/its)  bitini  bitlerini 
bizim (our)  bitimizi  bitlerimizi 
sizin (your)  bitinizi  bitlerinizi 
onların (their)  bitlerini  bitlerini 
dative  singular  plural 

benim (my)  bitime  bitlerime 
senin (your)  bitine  bitlerine 
onun (his/her/its)  bitine  bitlerine 
bizim (our)  bitimize  bitlerimize 
sizin (your)  bitinize  bitlerinize 
onların (their)  bitlerine  bitlerine 
locative  singular  plural 

benim (my)  bitimde  bitlerimde 
senin (your)  bitinde  bitlerinde 
onun (his/her/its)  bitinde  bitlerinde 
bizim (our)  bitimizde  bitlerimizde 
sizin (your)  bitinizde  bitlerinizde 
onların (their)  bitlerinde  bitlerinde 
ablative  singular  plural 

benim (my)  bitimden  bitlerimden 
senin (your)  bitinden  bitlerinden 
onun (his/her/its)  bitinden  bitlerinden 
bizim (our)  bitimizden  bitlerimizden 
sizin (your)  bitinizden  bitlerinizden 
onların (their)  bitlerinden  bitlerinden 
genitive  singular  plural 

benim (my)  bitimin  bitlerimin 
senin (your)  bitinin  bitlerinin 
onun (his/her/its)  bitinin  bitlerinin 
bizim (our)  bitimizin  bitlerimizin 
sizin (your)  bitinizin  bitlerinizin 
onların (their)  bitlerinin  bitlerinin 
A bit is a small amount of something, such as a bit that is the smallest amount of computer or electronic information storage. It can be set to 0 (false) or 1 (true), as machinereadable information. (It's like a light switch; either there is light or there is not.)
8 bits are called a byte.
