Prefixes for bit and byte
Decimal Value SI 10001 k kilo- 10002 M mega- 10003 G giga- 10004 T tera- 10005 P peta- 10006 E exa- 10007 Z zetta- 10008 Y yotta-	Binary Value IEC JEDEC 10241 Ki kibi- K kilo- 10242 Mi mebi- M mega- 10243 Gi gibi- G giga- 10244 Ti tebi- 10245 Pi pebi- 10246 Ei exbi- 10247 Zi zebi- 10248 Yi yobi-

In computer science a byte (pronounced "bite", IPA: /baɪt/) is a unit of measurement of information storage, most often consisting of eight bits. A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol to form a Decimal multiple or Kilo- (symbol k is a prefix in the SI and other systems of units denoting 103 or 1000 Mega- (symbol M) is an SI prefix in the SI system of units denoting a factor of 106, 1000000 (one Million For other meanings see Giga (disambiguation Giga- (symbol G is a prefix in the SI system of units denoting 109 teras- (symbol T) is a prefix in the SI system of units denoting 1012, or 1000000000000 (1 trillion In Physics and Mathematics, peta- (symbol P) is a prefix in the SI ( System of units) denoting 1015 exa- (symbol E) is a prefix in the SI system of units denoting 1018 or 1 000 000 000 000 000 000 zetta- (symbol Z) is an SI prefix in the SI ( System of units) denoting 1021 or 1 000 000 000 000 000 000 000 yotta- (symbol Y) is an SI prefix in the SI ( System of units) denoting 1024 or 1 000 000 000 000 000 000 000 000 IEC 60027 (formerly IEC 27) is the International Electrotechnical Commission 's standard on Letter symbols to be used in electrical technology. JEDEC Solid State Technology Association, formerly known as J oint E lectron D evice E ngineering C ouncil ( JEDEC) or Joint Computer science (or computing science) is the study and the Science of the theoretical foundations of Information and Computation and their Computer data storage, often called storage or memory, refers to Computer components devices and recording media that retain digital A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication In many computer architectures it is a unit of memory addressing. In Computer engineering, computer architecture is the conceptual design and fundamental operational structure of a Computer system Byte addressing refers to hardware architectures which support accessing individual Bytes of data rather than only larger units called words. In Computing, an address space defines a range of discrete addresses each of which may correspond to a physical or virtual Memory register, a network host

Originally, a byte was a small group of bits of a size convenient for data such as a single character from a Western character set. A character encoding consists of a code that pairs a sequence of characters from a given character set (sometimes incorrectly referred to as Code page Its size was generally determined by the number of possible characters in the supported character set and was chosen to be a divisor of the computer's word size; historically, bytes have ranged from five to twelve bits. In Computing, " word " is a term for the natural unit of data used by a particular computer design The popularity of IBM's System/360 architecture starting in the 1960s and the explosion of microcomputers based on 8-bit microprocessors in the 1980s has made eight bits by far the most common size for a byte. The IBM System/360 ( S/360) is a Mainframe computer system family announced by IBM on April 7, 1964. In Computer engineering, computer architecture is the conceptual design and fundamental operational structure of a Computer system microcomputer is a Computer with a Microprocessor as its Central processing unit. A microprocessor incorporates most or all of the functions of a Central processing unit (CPU on a single Integrated The term octet is widely used as a more precise synonym where ambiguity is undesirable (for example, in protocol definitions). 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 In computing, a protocol is a convention or standard that controls or enables the connection Communication, and Data transfer between two computing

There has been considerable confusion about the meanings of SI prefixes used with the word "byte", such as kilo- (k or K) and mega- (M), as shown in the chart Quantities of bytes. An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol to form a Decimal multiple or Since computer memory comes in powers of 2 rather than 10, the industry used binary estimates of the SI-prefixed quantities. Because of the confusion, a contract specifying a quantity of bytes must define what the prefixes mean in terms of the contract (i. e. , the alternative binary equivalents or the actual decimal values, or a binary estimate based on the actual values).

A byte is one of the basic integral data types in some programming languages, especially system programming languages. In computer science the term integer is used to refer to a Data type which represents some finite subset of the mathematical Integers These are also known as A programming language is an Artificial language that can be used to write programs which control the behavior of a machine particularly a Computer. System programming languages (otherwise known as applications languages) are Programming languages that are statically typed, allow arbitrarily complex

To make the meaning of the table absolutely clear: A kibibyte is made up of 1,024 bytes. A mebibyte is made up of 1,024 × 1,024 bytes. The figures in the column using 1,024 raised to powers of 1, 2, 3, 4 and so on are in units of bytes.

Contents 1 Meanings 2 History 3 Alternative words 4 Abbreviation/Symbol 5 Names for different units 6 See also 7 Notes

Meanings

The word "byte" has two closely related meanings:

1. A contiguous sequence of a fixed number of bits (binary digits). A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication The use of a byte to mean 8 bits has become nearly ubiquitous.
2. A contiguous sequence of bits within a binary computer that comprises the smallest addressable sub-field of the computer's natural word-size. In Computing, " word " is a term for the natural unit of data used by a particular computer design That is, the smallest unit of binary data on which meaningful computation, or natural data boundaries, could be applied. For example, the CDC 6000 series scientific mainframes divided their 60-bit floating-point words into 10 six-bit bytes. The CDC 6000 series was a family of Mainframe computers manufactured by Control Data Corporation in the 1960s These bytes conveniently held Hollerith data from punched cards, typically the upper-case alphabet and decimal digits. Herman Hollerith ( February 29, 1860 &ndash November 17, 1929) was a German-American statistician who developed a CDC also often referred to 12-bit quantities as bytes, each holding two 6-bit display code characters, due to the 12-bit I/O architecture of the machine. Display code is the 6-bit character set used by many computer systems manufactured by Control Data Corporation, notably the CDC 6600 in 1964 The PDP-10 used assembly instructions LDB and DPB to extract bytes — these operations survive today in Common Lisp. The PDP-10 was a Mainframe computer manufactured by Digital Equipment Corporation (DEC from the late 1960s on the name stands for "Programmed Data Processor Common Lisp, commonly abbreviated CL, is a dialect of the Lisp Programming language, published in ANSI standard document Information Bytes of six, seven, or nine bits were used on some computers, for example within the 36-bit word of the PDP-10. The PDP-10 was a Mainframe computer manufactured by Digital Equipment Corporation (DEC from the late 1960s on the name stands for "Programmed Data Processor The UNIVAC 1100/2200 series computers (now Unisys) addressed in both 6-bit (Fieldata) and 9-bit (ASCII) modes within its 36-bit word. The UNIVAC 1100/2200 series is a series of compatible 36-bit computer systems beginning with the UNIVAC 1107 in 1962, initially made by Sperry Rand Unisys Corporation ( based in Blue Bell, Pennsylvania, United States, and incorporated in Delaware, is a global provider of information technology Fieldata was a pioneering computer project run by the US Army Signal Corps in the late 1950s that intended to create a single standard for collecting and distributing American Standard Code for Information Interchange ( ASCII)

History

The term byte was coined by Dr. Werner Buchholz in July 1956, during the early design phase for the IBM Stretch computer. The IBM 7030, also known as Stretch, was IBM 's first Transistorized Supercomputer. ^[1][2][3] Originally it was defined in instructions by a 4-bit byte-size field, allowing from one to sixteen bits (the production design reduced this to a 3-bit byte-size field, allowing from one to eight bits to be represented by a byte); typical I/O equipment of the period used six-bit bytes. A fixed eight-bit byte size was later adopted and promulgated as a standard by the System/360. The IBM System/360 ( S/360) is a Mainframe computer system family announced by IBM on April 7, 1964. The term "byte" comes from "bite," as in the smallest amount of data a computer could "bite" at once. The spelling change not only reduced the chance of a "bite" being mistaken for a "bit," but also was consistent with the penchant of early computer scientists to make up words and change spellings. A byte was also often referred to as "an 8-bit byte", reinforcing the notion that it was a tuple of n bits, and that other sizes were possible.

1. A contiguous sequence of binary bits in a serial data stream, such as in modem or satellite communications, or from a disk-drive head, which is the smallest meaningful unit of data. These bytes might include start bits, stop bits, or parity bits, and thus could vary from 7 to 12 bits to contain a single 7-bit ASCII code.
2. A datatype or synonym for a datatype in certain programming languages. A data type in Programming languages is an attribute of a datum which tells the computer (and the programmer something about the kind of datum it is A programming language is an Artificial language that can be used to write programs which control the behavior of a machine particularly a Computer. C and C++, for example, defines byte as "addressable unit of data storage large enough to hold any member of the basic character set of the execution environment" (clause 3. tags please moot on the talk page first! --> In Computing, C is a general-purpose cross-platform block structured 6 of the C standard). Since the C char integral data type must contain at least 8 bits (clause 5. 2. 4. 2. 1), a byte in C is at least capable of holding 256 different values (signed or unsigned char does not matter). Various implementations of C and C++ define a "byte" as 8, 9, 16, 32, or 36 bits[1][2]. The actual number of bits in a particular implementation is documented as CHAR_BIT as implemented in the limits.h file. TemplateC_Standard_library --> limitsh is the header of the general purpose standard library of the C programming language Java's primitive byte data type is always defined as consisting of 8 bits and being a signed data type, holding values from −128 to 127.

Early microprocessors, such as Intel 8008 (the direct predecessor of the 8080, and then 8086) could perform a small number of operations on four bits, such as the DAA (decimal adjust) instruction, and the "half carry" flag, that were used to implement decimal arithmetic routines. The Intel 8008 was an early byte-oriented Microprocessor designed and manufactured by Intel and introduced in April 1972 The 8086 is a 16-bit Microprocessor chip designed by Intel and introduced on the market in 1978 which gave rise to the X86 architecture A nibble (often nybble) is the Computing term for a four- Bit aggregation or half an octet (an octet being an 8-bit Byte These four-bit quantities were called "nybbles," in homage to the then-common 8-bit "bytes. A nibble (often nybble) is the Computing term for a four- Bit aggregation or half an octet (an octet being an 8-bit Byte "

Alternative words

Following "bit," "byte," and "nybble," there have been some analogical attempts to construct unambiguous terms for bit blocks of other sizes. ^[4] All of these are strictly jargon, and not very common. For Wikipedia jargon see WikipediaGlossary. For hacker slang see Jargon File.

• 2 bits: crumb, quad, quarter, tayste, tydbit
• 4 bits: nibble, nybble
• 5 bits: nickel, nyckle
• 10 bits: deckle
• 16 bits: plate, playte, chomp, chawmp (on a 32-bit machine)
• 18 bits: chomp, chawmp (on a 36-bit machine)
• 32 bits: dinner, dynner, gawble (on a 32-bit machine)
• 48 bits: gobble, gawble (under circumstances that remain obscure)

Abbreviation/Symbol

IEEE 1541 and Metric-Interchange-Format specify "B" as the symbol for byte (e. A nibble (often nybble) is the Computing term for a four- Bit aggregation or half an octet (an octet being an 8-bit Byte g. MB means megabyte), while IEC 60027 seems silent on the subject. IEC 60027 (formerly IEC 27) is the International Electrotechnical Commission 's standard on Letter symbols to be used in electrical technology. Furthermore, B means bel (see decibel), another (logarithmic) unit used in the same field. The decibel ( dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity relative to The use of B to stand for bel is consistent with the metric system convention that capitalized symbols are for units named after a person (in this case Alexander Graham Bell); usage of a capital B to stand for byte is not consistent with this convention. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout There is little danger of confusing a byte with a bel because the bel's sub-multiple the decibel (dB) is usually preferred, while use of the decibyte (dB) is extremely rare. The decibel ( dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity relative to

The unit symbol "kb" with a lowercase "b" is a commonly used abbreviation for "kilobyte". Use of this abbreviation leads to confusion with the alternative use of "kb" to mean "kilobit". A kilobit is a unit of information abbreviated kbit (or kb) The standard definition is 1 kilobit = 103 bit = 1000 Bit. IEEE 1541 specifies "b" as the symbol for bit; however the IEC 60027 and Metric-Interchange-Format specify "bit" (e. A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication The International Electrotechnical Commission ( IEC) is a not-for-profit, non-governmental international Standards organization that prepares and publishes g. Mbit for megabit) for the symbol, achieving maximum disambiguation from byte.

French-speaking countries sometimes use an uppercase "o" for "octet". This is not consistent with SI because of the risk of confusion with the zero, and the convention that capitals are reserved for unit names derived from proper names, such as the ampere (whose symbol is A) and joule (symbol J), versus the second (symbol s) and metre (symbol m). The ampere, in practice often shortened to amp, (symbol A is a unit of Electric current, or amount of Electric charge per second The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity The second ( SI symbol s) sometimes abbreviated sec, is the name of a unit of Time, and is the International System of Units The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International

Lowercase "o" for "octet" is a commonly used symbol in several non-English-speaking countries, and is also used with metric prefixes (for example, "ko" and "Mo"). 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

Names for different units

The prefixes used for byte measurements are usually the same as the SI prefixes used for other measurements, but have slightly different values. An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol to form a Decimal multiple or The former are based on powers of 1,024 (2¹⁰), a convenient binary number, while the SI prefixes are based on powers of 1,000 (10³), a convenient decimal number. The table below illustrates these differences. See binary prefix for further discussion. In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two

Prefix	Name	SI Meaning	Binary meaning	Size difference
k	kilo	103   = 10001	210 = 10241	2. An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol to form a Decimal multiple or In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two 40%
M	mega	106   = 10002	220 = 10242	4. 86%
G	giga	109   = 10003	230 = 10243	7. 37%
T	tera	1012 = 10004	240 = 10244	9. 95%
P	peta	1015 = 10005	250 = 10245	12. 59%
E	exa	1018 = 10006	260 = 10246	15. 29%
Z	zega	1021 = 10007	270 = 10247	18. 67%

Sometimes "K" is used intead of "k". The use of "K" as a prefix has no meanings for the SI.

In 1998, the IEC, then the IEEE, published a new standard describing binary prefixes:

Prefix	Name
kibi	binary kilo	1 kibibyte (KiB)	210 bytes	1024 B
mebi	binary mega	1 mebibyte (MiB)	220 bytes	1024 KiB
gibi	binary giga	1 gibibyte (GiB)	230 bytes	1024 MiB
tebi	binary tera	1 tebibyte (TiB)	240 bytes	1024 GiB
pebi	binary peta	1 pebibyte (PiB)	250 bytes	1024 TiB
exbi	binary exa	1 exbibyte (EiB)	260 bytes	1024 PiB

Fractional information is usually measured in bits, nibbles, nats, or bans, where the later two are used especially in the context of information theory and not usually with computing in general. The Institute of Electrical and Electronics Engineers or IEEE (read eye-triple-e) is an international Non-profit, professional organization In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two A kibibyte (a contraction of ki lo bi nary byte) is a unit of Information or Computer storage, established by the International A mebibyte (a contraction of me ga bi nary byte) is a unit of Information or Computer storage, abbreviated MiB. A gibibyte (a contraction of gi ga bi nary byte) is a unit of Information or Computer storage, abbreviated GiB. A tebibyte (a contraction of te ra bi nary byte) is a unit of Information or Computer storage, abbreviated TiB. A pebibyte (a contraction of pe ta bi nary byte) is a unit of Information or Computer storage, abbreviated PiB. An exbibyte (a contraction of ex a bi nary byte) is a unit of Information or Computer storage, abbreviated EiB. Information as a concept has a diversity of meanings from everyday usage to technical settings A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication 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 nat (sometimes also nit or even nepit) is a Logarithmic unit of Information or entropy, based on Natural logarithms and A ban, sometimes called a hartley (symbol Hart) or a dit (abbreviation of d ecimal dig' it') is a Logarithmic unit which Information theory is a branch of Applied mathematics and Electrical engineering involving the quantification of Information.

See also

• Bit
• Word (computing)

Notes

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