A bit is a binary digit, taking a value of either 0 or 1. The binary numeral system, or base-2 number system, is a Numeral system that represents numeric values using two symbols usually 0 and 1. In Mathematics and Computer science, a digit is a symbol (a number symbol e For example, the number 10010111 is 8 bits long, or in most cases, one modern PC byte. A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. Binary digits are a basic unit of information storage and communication in digital computing and digital information theory. Information as a concept has a diversity of meanings from everyday usage to technical settings Computer data storage, often called storage or memory, refers to Computer components devices and recording media that retain digital In Telecommunications transmission is the process of sending propagating and receiving an analogue or digital information signal over a physical point-to-point or Computing is usually defined like the activity of using and developing Computer technology Computer hardware and software. Information theory is a branch of Applied mathematics and Electrical engineering involving the quantification of Information. Information theory also often uses the natural digit, called either a nit or a nat. A nat (sometimes also nit or even nepit) is a Logarithmic unit of Information or entropy, based on Natural logarithms and A nat (sometimes also nit or even nepit) is a Logarithmic unit of Information or entropy, based on Natural logarithms and Quantum computing also uses qubits, a single piece of information with a probability of being true. A quantum computer is a device for Computation that makes direct use of distinctively Quantum mechanical Phenomena, such as superposition A qubit is not to be confused with a Cubit, which is an ancient measure of length

The bit is also a unit of measurement, the information capacity of one binary digit. It has the symbol bit, or b (see discussion below). The unit is also known as the shannon, with symbol Sh. Claude Elwood Shannon (April 30 1916 – February 24 2001 an American Electronic engineer and Mathematician, is "the father of Information

Binary digit

Claude E. Shannon first used the word bit in his 1948 paper A Mathematical Theory of Communication. Claude Elwood Shannon (April 30 1916 – February 24 2001 an American Electronic engineer and Mathematician, is "the father of Information "A Mathematical Theory of Communication" is an influential 1948 article by Mathematician Claude E 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". John Wilder Tukey ( June 16, 1915 &ndash July 26, 2000) was an American Statistician. 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. Vannevar Bush ( March 11, 1890 &ndash June 30, 1974; pronounced "VAN-ee-var" ˈvæˌniː ^[1]

A bit of storage is like a light switch; it can be either on (1) or off (0). A single bit is a one or a zero, a true or a false, a "flag" which is "on" or "off", or in general, the quantity of information required to distinguish two mutually exclusive equally probable states from each other. In Computer science and Automata theory, a state is a unique configuration of information in a program or machine Gregory Bateson defined a bit as "a difference that makes a difference". Gregory Bateson ( 9 May 1904 – 4 July 1980) was a British anthropologist, social scientist, linguist [1]

Representation

Transmission

Bits can be implemented in many forms depending on context. For example, in digital circuitry in most computing devices as well as flash memories, a bit is an electrical pulse generated by the internal clock in the control unit or data register. Digital electronics are Electronics systems that use Digital signals Digital electronics are representations of Boolean algebra also see For devices using positive logic, a logical 1 (true value) is represented by up to 5 volts, while a logical 0 (false value) is represented by 0 volt. The volt (symbol V) is the SI derived unit of electric Potential difference or Electromotive force.

Storage

On storage devices like 1,200,000nm-thick CD-ROMs, a bit is mechanically etched by intensive laser beam as a pit about 168nm deep and 670nm wide of variable length (depending on data type) on concentric tracks spaced 1,600nm apart. CD-ROM (an initialism of "Compact Disc Read-Only Memory " is a pre-pressed Compact Disc that contains data accessible to but not writable The total length of the track in a 650MB disk thus may span several kilometres. The light of the reading laser is reflected back into the laser, which then picks up that light with a sensor. The transition between a pit and a ground means a 1, and a short period of time on the same level is a 0. No more than 11 consequent zeros may occur, because the laser receives no state change during consequent zeros and has to rely on a timer to know the amount of zeros, whose accuracy is limited. CD-Rs work on the same theory, except that they use dyes instead of pits and ground. A CD-R ( C ompact D isc- R ecordable is a variation of the Compact Disc invented by Philips and Sony. A dye can generally be described as a Colored substance that has an affinity to the substrate to which it is being applied [2]

Bits can also be represented magnetically, such as in magnetic tapes and cassettes. A magnet (from Greek grc μαγνήτης λίθος " Magnesian stone" is a material or object that produces a Magnetic field. The Compact Cassette, often referred to as audio cassette, cassette tape, cassette, or simply tape, is a Magnetic tape sound

Unit

It is important to differentiate between the use of "bit" in referring to a discrete storage unit and the use of "bit" in referring to a statistical unit of information. The bit, as a discrete storage unit, can by definition store only 0 or 1. A statistical bit is the amount of information that, on average, can be stored in a discrete bit. It is thus the amount of information carried by a choice between two equally likely outcomes. One bit corresponds to about 0. 693 nats (ln(2)), or 0. A nat (sometimes also nit or even nepit) is a Logarithmic unit of Information or entropy, based on Natural logarithms and 301 hartleys (log₁₀(2)). A ban, sometimes called a hartley (symbol Hart) or a dit (abbreviation of d ecimal dig' it') is a Logarithmic unit which

Consider, for example, a computer file with one thousand 0s and 1s which can be losslessly compressed to a file of five hundred 0s and 1s (on average, over all files of that kind). A computer file is a block of Arbitrary Information, or resource for storing information which is available to a Computer program and is usually Lossless data compression is a class of Data compression Algorithms that allows the exact original data to be reconstructed from the compressed data The original file, although having 1,000 bits of storage, has at most 500 bits of information entropy, since information is not destroyed by lossless compression. A file can have no more information theoretical bits than it has storage bits. If these two ideas need to be distinguished, sometimes the name bit is used when discussing data storage while shannon is used for the statistical bit. However, most of the time, the meaning is clear from the context.

Abbreviation/symbol

No uniform agreement has been reached yet about what the official unit symbols for bit and byte should be. A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. One commonly-quoted standard, the International Electrotechnical Commission's IEC 60027, specifies that "bit" should be the unit symbol for the unit bit (e. The International Electrotechnical Commission ( IEC) is a not-for-profit, non-governmental international Standards organization that prepares and publishes IEC 60027 (formerly IEC 27) is the International Electrotechnical Commission 's standard on Letter symbols to be used in electrical technology. g. "kbit" for kilobit). In the same standard, the symbols "o" and "B" are specified for the byte. A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science.

The other commonly-quoted relevant standard, IEEE 1541, specifies "b" to be the unit symbol for bit and "B" to be that for byte. This convention is also widely used in computing, but has so far not been considered acceptable internationally for several reasons:

• both these symbols are already used for other units: "b" for barn and "B" for bel;
• "bit" is already short for "binary digit", so there is little reason to abbreviate it any further;
• it is customary to start a unit symbol with an uppercase letter only if the unit was named after a person (see also Claude Émile Jean-Baptiste Litre);
• instead of byte, the term octet (unit symbol: "o") is used in some fields and in some French-speaking countries, which adds to the difficulty of agreeing on an international symbol;
• "b" is occasionally also used for byte, along with "bit" for bit. A barn (symbol b) is a unit of Area. While the barn is not an SI unit it is accepted (although discouraged for use with the SI The decibel ( dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity relative to Claude Émile Jean-Baptiste Litre is a fictional character created in 1977 by Kenneth Woolner of the University of Waterloo in order to justify the use of a capital In Computing, an octet is a grouping of eight Bits Octet, with the only exception noted below always refers to an entity having exactly eight

The unit bel is rarely used by itself (only as decibel, "dB", which is unlikely to be confused with a decibyte), so the chances of conflict with "B" for byte are quite small, even though both units are very commonly used in the same fields (e. g. , telecommunication).

More than one bit

A byte is a collection of bits, originally differing in size depending on the context but now almost always eight bits. A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. Eight-bit bytes, also known as octets, can represent 256 values (2⁸ values, 0–255). In Computing, an octet is a grouping of eight Bits Octet, with the only exception noted below always refers to an entity having exactly eight A four-bit quantity is known as a nibble, and can represent 16 values (2⁴ values, 0–15). A nibble (often nybble) is the Computing term for a four- Bit aggregation or half an octet (an octet being an 8-bit Byte A rarely used term, crumb, can refer to a two-bit quantity, and can represent 4 values (2² values, 0–3).

"Word" is a term for a slightly larger group of bits, but it has no standard size. In Computing, " word " is a term for the natural unit of data used by a particular computer design It represents the size of one register in a Computer-CPU. A computer is a Machine that manipulates data according to a list of instructions. In the IA-32 architecture more commonly known as x86-32, 16 bits are called a "word" (with 32 bits being a double word or dword), but other architectures have word sizes of 8, 32, 64, 80 or others. IA-32 ( Intel Architecture 32-bit) often generically called X86 or x86-32, is the Instruction set architecture of Intel In Computing, " word " is a term for the natural unit of data used by a particular computer design

Terms for large quantities of bits can be formed using the standard range of SI prefixes, e. g. , kilobit (kbit), megabit (Mbit) and gigabit (Gbit). 943 KILO is a radio station sponsored out of Colorado Springs and Pueblo, Colorado. A kilobit is a unit of information abbreviated kbit (or kb) The standard definition is 1 kilobit = 103 bit = 1000 Bit. A megabit is a unit of Information or computer storage abbreviated Mbit (or Mb) For other meanings see Giga (disambiguation Giga- (symbol G is a prefix in the SI system of units denoting 109 A gigabit is a unit of information or computer storage abbreviated Gbit (or Gb) Note that much confusion exists regarding these units and their abbreviations (see above).

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 being used must be known. In Computing, the most significant bit ( msb) is the Bit position in a binary number having the greatest value In Computing, the least significant bit ( lsb) is the Bit position in a binary Integer giving the units value that is determining

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. In Computer programming, a bitwise operation operates on one or two Bit patterns or binary numerals at the level of their individual Bits On most

Telecommunications or computer network transfer rates are usually described in terms of bits per second (bps), not to be confused with baud. A computer network is a group of interconnected Computers. Networks may be classified according to a wide variety of characteristics In Telecommunications and Computing, bitrate (sometimes written bit rate, data rate or as a Variable R or f b In Telecommunications and Electronics, baud (ˈbɔːd unit symbol "Bd" is synonymous to symbols/s or pulses/s.

See also

• Byte
• Integral data type
• Bitstream
• Information entropy
• Binary arithmetic
• Ternary numeral system

Notes