53-606: Widmer is a surname. Notable people with the surname include: Albert Widmer, inventor of 8b/10b encoding Arthur Widmer (1914–2006), American film special effects pioneer Carolyn Ladd Widmer (1902–1991), academic dean at the University of Connecticut Daniel Widmer , Swiss curler Edward L. Widmer (born 1963), historian, speechwriter, and librarian Eric Widmer (born 1940), American scholar and educator Gabrielle Oberhänsli-Widmer (born 1957), Professor of Jewish studies at
106-409: 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 or least significant bit depending on the context. Similar to torque and energy in physics; information-theoretic information and data storage size have the same dimensionality of units of measurement , but there
159-502: A unit of information , the bit is also known as a shannon , named after Claude E. Shannon . The symbol for the binary digit is either "bit", per the IEC 80000-13 :2008 standard, or the lowercase character "b", per the IEEE 1541-2002 standard. Use of the latter may create confusion with the capital "B" which is the international standard symbol for the byte. The encoding of data by discrete bits
212-456: A "comma" symbol) needs to be used to define the alignment of the 10-bit symbols. They are referred to as K.x.y and have different encodings from any of the D.x.y symbols. Because 8b/10b encoding uses 10-bit symbols to encode 8-bit words, some of the possible 1024 (10 bit, 2 ) symbols can be excluded to grant a run-length limit of 5 consecutive equal bits and to ensure the difference between the count of zeros and ones to be no more than two. Some of
265-436: A 10-bit output value with odd disparity, or to one with even disparity. This mapping is usually done at the time when parallel input data is converted into a serial output stream for transmission over a fibre channel link. The odd/even selection is done in such a way that a long-term zero disparity between ones and zeroes is maintained. This is often called "DC balancing". The 8-bit to 10-bit conversion scheme uses only 512 of
318-421: A 6- or 4-bit code is used that has a non-zero disparity (count of ones minus count of zeros; i.e., −2 or +2), the choice of positive or negative disparity encodings must be the one that toggles the running disparity. In other words, the non zero disparity codes alternate. 8b/10b coding is DC-free, meaning that the long-term ratio of ones and zeros transmitted is exactly 50%. To achieve this, the difference between
371-482: A Bell Labs memo on 9 January 1947 in which he contracted "binary information digit" to simply "bit". A bit can be stored by a digital device or other physical system that exists in either of two possible distinct states . These may be the two stable states of a flip-flop , two positions of an electrical switch , two distinct voltage or current levels allowed by a circuit , two distinct levels of light intensity , two directions of magnetization or polarization ,
424-429: A bit was represented by the polarity of magnetization of a certain area of a ferromagnetic 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 items such as metro tickets and some credit cards . In modern semiconductor memory , such as dynamic random-access memory ,
477-557: A corresponding 8b data byte. They are used for low-level control functions. For instance, in Fibre Channel, K28.5 is used at the beginning of four-byte sequences (called "Ordered Sets") that perform functions such as Loop Arbitration, Fill Words, Link Resets, etc. Resulting from the 5b/6b and 3b/4b tables the following 12 control symbols are allowed to be sent: † Within the control symbols, K.28.1, K.28.5, and K.28.7 are "comma symbols". Comma symbols are used for synchronization (finding
530-459: A false misaligned comma symbol overlapping the two codes. A sequence of multiple K.28.7 codes is not allowable in any case, as this would result in undetectable misaligned comma symbols. K.28.7 is the only comma symbol that cannot be the result of a single bit error in the data stream. After the above-mentioned IBM patent expired, the scheme became even more popular and was chosen as a DC-free line code for several communication technologies. Among
583-557: A heavy use in digital audio storage applications, namely A differing but related scheme is used for audio CDs and CD-ROMs : Note that 8b/10b is the encoding scheme, not a specific code. While many applications do use the same code, there exist some incompatible implementations; for example, Transition Minimized Differential Signaling , which also expands 8 bits to 10 bits, but it uses a completely different method to do so. 64b/66b encoding , introduced for 10 Gigabit Ethernet 's 10GBASE-R Physical Medium Dependent (PMD) interfaces,
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#1732901557762636-404: A time in serial transmission , and by a multiple number of bits in parallel transmission . A bitwise operation 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. In the earliest non-electronic information processing devices, such as Jacquard's loom or Babbage's Analytical Engine , a bit
689-504: Is a lower-overhead alternative to 8b/10b encoding, having a two-bit overhead per 64 bits (instead of eight bits) of encoded data. This scheme is considerably different in design from 8b/10b encoding, and does not explicitly guarantee DC balance, short run length, and transition density (these features are achieved statistically via scrambling ). 64b/66b encoding has been extended to the 128b/130b and 128b/132b encoding variants for PCI Express 3.0 and USB 3.1 , respectively, replacing
742-421: Is different from Wikidata All set index articles 8b/10b encoding In telecommunications , 8b/10b is a line code that maps 8-bit words to 10-bit symbols to achieve DC balance and bounded disparity, and at the same time provide enough state changes to allow reasonable clock recovery . This means that the difference between the counts of ones and zeros in a string of at least 20 bits
795-486: Is in general no meaning to adding, subtracting or otherwise combining the units mathematically, although one may act as a bound on the other. Units of information used in information theory include the shannon (Sh), the natural unit of information (nat) and the hartley (Hart). One shannon is the maximum amount of information needed to specify the state of one bit of storage. These are related by 1 Sh ≈ 0.693 nat ≈ 0.301 Hart. Some authors also define
848-554: 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 . Certain bitwise computer processor instructions (such as bit set ) operate at
901-475: Is no more than two, and that there are not more than five ones or zeros in a row. This helps to reduce the demand for the lower bandwidth limit of the channel necessary to transfer the signal. An 8b/10b code can be implemented in various ways with focus on different performance parameters. One implementation was designed by K. Odaka for the DAT digital audio recorder. Kees Schouhamer Immink designed an 8b/10b code for
954-414: Is positive when D.07 is encountered 000111 is used, and if it is negative 111000 is used. Likewise, if RD is positive when D.x.3 is encountered 0011 is used, and if it is negative 1100 is used. This is accurately reflected in the charts below, but is worth making additional mention of as these are the only two sub-blocks with equal numbers of 1s and 0s that each have two possible encodings. † also used for
1007-455: Is used for 4GFC and 8GFC variants; for 10GFC and 16GFC variants, it is 64b/66b. The Fibre Channel FC1 data link layer is then responsible for implementing the 8b/10b encoding and decoding of signals. The Fibre Channel 8b/10b coding scheme is also used in other telecommunications systems. Data is expanded using an algorithm that creates one of two possible 10-bit output values for each input 8-bit value. Each 8-bit input value can map either to
1060-482: The DCC audio recorder. The IBM implementation was described in 1983 by Al Widmer and Peter Franaszek . As the scheme name suggests, eight bits of data are transmitted as a 10-bit entity called a symbol , or character . The low five bits of data are encoded into a 6-bit group (the 5b/6b portion) and the top three bits are encoded into a 4-bit group (the 3b/4b portion). These code groups are concatenated together to form
1113-440: The surname Widmer . If an internal link intending to refer to a specific person led you to this page, you may wish to change that link by adding the person's given name (s) to the link. Retrieved from " https://en.wikipedia.org/w/index.php?title=Widmer&oldid=1159039048 " Categories : Surnames Swiss-language surnames Hidden categories: Articles with short description Short description
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#17329015577621166-410: The yottabit (Ybit). 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
1219-440: The 10-bit symbol that is transmitted on the wire. The data symbols are often referred to as D.x.y where x ranges over 0–31 and y over 0–7. Standards using the 8b/10b encoding also define up to 12 special symbols (or control characters ) that can be sent in place of a data symbol . They are often used to indicate start-of-frame, end-of-frame, link idle, skip and similar link-level conditions. At least one of them (i.e.
1272-449: 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 , or opaque spots printed on glass discs by photolithographic techniques. In the 1950s and 1960s, these methods were largely supplanted by magnetic storage devices such as magnetic-core memory , magnetic tapes , drums , and disks , where
1325-414: The 256 possible 8-bit words can be encoded in two different ways. Using these alternative encodings, the scheme is able to achieve long-term DC-balance in the serial data stream. This permits the data stream to be transmitted through a channel with a high-pass characteristic, for example Ethernet 's transformer -coupled unshielded twisted pair or optical receivers using automatic gain control. Note that in
1378-490: The 3b/4b code portion used for control symbols K.x.7 is the same as that for D.x.A7. Any other D.x.A7 code can't be used as it would result in chances for misaligned comma sequences. ‡ Only K.28.1, K.28.5, and K.28.7 generate comma symbols, that contain a bit sequence of five 0s or 1s. The symbol has the format 11 0000 0 1xx or 00 1111 1 0xx. The control symbols within 8b/10b are 10b symbols that are valid sequences of bits (no more than six 1s or 0s) but do not have
1431-580: The 5b/6b code of K.x.7 ‡ exclusively used for the 5b/6b code of K.28.y † For D.x.7, either the Primary (D.x.P7), or the Alternate (D.x.A7) encoding must be selected in order to avoid a run of five consecutive 0s or 1s when combined with the preceding 5b/6b code. Sequences of exactly five identical bits are used in comma symbols for synchronization issues. D.x.A7 is used only With x = 23, x = 27, x = 29, and x = 30,
1484-509: The 8b/10b encoding in earlier revisions of each standard. Bit The bit is the most basic unit of information in computing and digital communication . The name is a portmanteau of binary digit . The bit represents a logical state with one of two possible values . These values are most commonly represented as either " 1 " or " 0 " , but other representations such as true / false , yes / no , on / off , or + / − are also widely used. The relation between these values and
1537-694: The University of Freiburg Gianni Widmer (1892–1971), flight pioneer Kurt Widmer (1940–2023), Swiss baritone Marise Widmer , American rower Markus Widmer , Swiss curler Pierre Widmer (1912–1999), French Mennonite pastor Samuel Widmer (1948–2017) Swiss physician, psychiatrist, psychotherapist and author Sigmund Widmer (1919–2003), Swiss politician Silvan Widmer (born 1993), Swiss footballer See also [ edit ] Widmer Brothers Brewery , an American brewery founded in 1984 in Portland, Oregon by brothers Kurt and Rob Widmer [REDACTED] Surname list This page lists people with
1590-419: The alignment of the 8b/10b codes within a bit-stream). If K.28.7 is not used, the unique comma sequences 00 11111 0 or 11 00000 1 cannot inadvertently appear at any bit position within any combination of normal codes. ‡ If K.28.7 is allowed in the actual coding, a more complex definition of the synchronization pattern than suggested by † needs to be used, as a combination of K.28.7 with several other codes forms
1643-409: The ambiguity of relying on the underlying hardware design, the unit octet was defined to explicitly denote a sequence of eight bits. Computers usually manipulate bits in groups of a fixed size, conventionally named " words ". 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
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1696-400: The areas in which 8b/10b encoding finds application are the following: The FC-0 standard defines what encoding scheme is to be used (8b/10b or 64b/66b) in a Fibre Channel system – higher speed variants typically use 64b/66b to optimize bandwidth efficiency (since bandwidth overhead is 20% in 8b/10b versus approximately 3% (~ 2/66) in 64b/66b systems). Thus, 8b/10b encoding
1749-424: The average. This principle is the basis of 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
1802-411: The control (K) codes. All of the codes can be described by stating 3 octal values. This is done with a naming convention of "Dxx.x" or "Kxx.x". (Note that the tables in earlier sections are using decimal, rather than octal, values for Dxx.x or Kxx.x) Example: Now these bits are converted to decimal in the way they are paired. Input data E 8B/10B = D03.6 Encoding schemes 8b/10b have found
1855-421: The current running disparity of the signal, the encoding engine selects which of the two possible six- or four-bit sequences to send for the given data. Obviously, if the six-bit or four-bit code has equal numbers of ones and zeros, there is no choice to make, as the disparity would be unchanged, with the exceptions of sub-blocks D.07 (00111) and D.x.3 (011). In either case the disparity is still unchanged, but if RD
1908-415: The early 21st century, retail personal or server computers have a word size of 32 or 64 bits. The International System of Units 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 (10 ) through yotta (10 ) increment by multiples of one thousand, and the corresponding units are the kilobit (kbit) through
1961-431: The following tables, for each input byte (represented as HGF EDCBA ), A denotes the least significant bit (LSB), and H the most significant (MSB). The output gains two extra bits, i and j . The bits are sent from LSB to MSB: a, b, c, d, e, i , f, g, h, and j ; i.e., the 5b/6b code followed by the 3b/4b code. This ensures the uniqueness of the special bit sequence in the comma symbols. The residual effect on
2014-409: 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 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
2067-530: The number of ones transmitted and the number of zeros transmitted is always limited to ±2, and at the end of each symbol, it is either +1 or −1. This difference is known as the running disparity (RD). This scheme needs only two states for the running disparity of +1 and −1. It starts at −1. For each 5b/6b and 3b/4b code with an unequal number of ones and zeros, there are two bit patterns that can be used to transmit it: one with two more "1" bits, and one with all bits inverted and thus two more zeros. Depending on
2120-408: The orientation of reversible double stranded DNA , etc. Bits can be implemented in several 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 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
2173-443: 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. A contiguous group of binary digits is commonly called a bit string , a bit vector, or a single-dimensional (or multi-dimensional) bit array . A group of eight bits is called one byte , but historically
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2226-425: The possible 1024 output values. Of the remaining 512 unused output values, most contain either too many ones (or too many zeroes) and therefore are not allowed. This still leaves enough spare 10-bit odd+even coding pairs to allow for at least 12 special non-data characters. The codes that represent the 256 data values are called the data (D) codes. The codes that represent the 12 special non-data characters are called
2279-517: The representation of 0 . Different logic families require different voltages, and variations are allowed to account for component aging and noise immunity. For example, in transistor–transistor logic (TTL) and compatible circuits, digit values 0 and 1 at the output of a device are represented by no higher than 0.4 V and no lower than 2.6 V, respectively; while TTL inputs are specified to recognize 0.8 V or below as 0 and 2.2 V or above as 1 . Bits are transmitted one at
2332-424: 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. A string of four bits is usually a nibble . In information theory , one bit is the information entropy of a random binary 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
2385-515: The stream to the number of zero and one bits transmitted is maintained as the running disparity ( RD ) and the effect of slew is balanced by the choice of encoding for following symbols. The 5b/6b code is a paired disparity code , and so is the 3b/4b code. Each 6- or 4-bit code word has either equal numbers of zeros and ones (a disparity of zero), or comes in a pair of forms, one with two more zeros than ones (four zeros and two ones, or three zeros and one one, respectively) and one with two less. When
2438-552: The thickness of alternating black and white lines. The bit is not defined in the International System of Units (SI). However, the International Electrotechnical Commission issued standard IEC 60027 , 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
2491-556: 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
2544-444: The two values of a bit may be represented by two levels of electric charge stored in a capacitor . In certain types of programmable logic arrays and read-only memory , a bit may be represented by the presence or absence of a conducting path at a certain point of a circuit. In optical discs , a bit is encoded as the presence or absence of a microscopic pit on a reflective surface. In one-dimensional bar codes , bits are encoded as
2597-447: 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. 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
2650-460: 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 paper card or tape . The first electrical devices for discrete logic (such as elevator and traffic light control circuits , telephone switches , 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 tubes , starting in
2703-503: 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 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 Werner Buchholz in June 1956, which historically
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#17329015577622756-541: Was used in the punched cards invented by Basile Bouchon and Jean-Baptiste Falcon (1732), developed by Joseph Marie Jacquard (1804), and later adopted by Semyon Korsakov , Charles Babbage , Herman Hollerith , and early computer manufacturers like IBM . A 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 carrying one bit of information. The encoding of text by bits
2809-405: Was used to represent the group of bits used to encode a single character of text (until UTF-8 multibyte encoding took over) in a computer and for this reason it was used as the basic addressable element in many computer architectures . 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
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