Byte

byte
Unit systemunits derived from bit
Unit ofdigital information, data size
SymbolB or (when referring to exactly 8 bits) o

The byte is a unit of digital information that most commonly consists of eight bits, representing a binary number. Historically, the byte was the number of bits used to encode a single character of text in a computer[1][2] and for this reason it is the smallest addressable unit of memory in many computer architectures.

The size of the byte has historically been hardware dependent and no definitive standards existed that mandated the size – byte-sizes from 1[3] to 48 bits[4] are known to have been used in the past.[5][6] Early character encoding systems often used six bits, and machines using six-bit and nine-bit bytes were common into the 1960s. These machines most commonly had memory words of 12, 24, 36, 48 or 60 bits, corresponding to two, four, six, eight or 10 six-bit bytes. In this era, bytes in the instruction stream were often referred to as syllables, before the term byte became common.

The modern de-facto standard of eight bits, as documented in ISO/IEC 2382-1:1993, is a convenient power of two permitting the values 0 through 255 for one byte.[7] The international standard IEC 80000-13 codified this common meaning. Many types of applications use information representable in eight or fewer bits and processor designers optimize for this common usage. The popularity of major commercial computing architectures has aided in the ubiquitous acceptance of the eight-bit size.[8] Modern architectures typically use 32- or 64-bit words, built of four or eight bytes.

The unit symbol for the byte was designated as the upper-case letter B by the International Electrotechnical Commission (IEC) and Institute of Electrical and Electronics Engineers (IEEE)[9] in contrast to the bit, whose IEEE symbol is a lower-case b. Internationally, the unit octet, symbol o, explicitly denotes a sequence of eight bits, eliminating the ambiguity of the byte.[10][11]

History

The term byte was coined by Werner Buchholz in June 1956,[3][12][13][a] during the early design phase for the IBM Stretch[14][15][1][12][13][16][17] computer, which had addressing to the bit and variable field length (VFL) instructions with a byte size encoded in the instruction.[12] It is a deliberate respelling of bite to avoid accidental mutation to bit.[1][12][18]

Another origin of byte for bit groups smaller than a machine's word size (and in particular groups of four bits) is on record by Louis G. Dooley, who claimed he coined the term while working with Jules Schwartz and Dick Beeler on an air defense system called SAGE at MIT Lincoln Laboratory in ca. 1956/1957, which was jointly developed by Rand, MIT, and IBM.[19][20] Later on, Schwartz's language JOVIAL actually used the term, but he recalled vaguely that it was derived from AN/FSQ-31.[21][20]

Early computers used a variety of four-bit binary coded decimal (BCD) representations and the six-bit codes for printable graphic patterns common in the U.S. Army (FIELDATA) and Navy. These representations included alphanumeric characters and special graphical symbols. These sets were expanded in 1963 to seven bits of coding, called the American Standard Code for Information Interchange (ASCII) as the Federal Information Processing Standard, which replaced the incompatible teleprinter codes in use by different branches of the U.S. government and universities during the 1960s. ASCII included the distinction of upper- and lowercase alphabets and a set of control characters to facilitate the transmission of written language as well as printing device functions, such as page advance and line feed, and the physical or logical control of data flow over the transmission media.[17] During the early 1960s, while also active in ASCII standardization, IBM simultaneously introduced in its product line of System/360 the eight-bit Extended Binary Coded Decimal Interchange Code (EBCDIC), an expansion of their six-bit binary-coded decimal (BCDIC) representation used in earlier card punches.[22] The prominence of the System/360 led to the ubiquitous adoption of the eight-bit storage size,[17][15][12] while in detail the EBCDIC and ASCII encoding schemes are different.

In the early 1960s, AT&T introduced digital telephony first on long-distance trunk lines. These used the eight-bit µ-law encoding. This large investment promised to reduce transmission costs for eight-bit data.

The development of eight-bit microprocessors in the 1970s popularized this storage size. Microprocessors such as the Intel 8008, the direct predecessor of the 8080 and the 8086, used in early personal computers, could also perform a small number of operations on the four-bit pairs in a byte, such as the decimal-add-adjust (DAA) instruction. A four-bit quantity is often called a nibble, also nybble, which is conveniently represented by a single hexadecimal digit.

The term octet is used to unambiguously specify a size of eight bits.[17][11] It is used extensively in protocol definitions.

Historically, the term octad or octade was used to denote eight bits as well at least in Western Europe;[23][24] however, this usage is no longer common. The exact origin of the term is unclear, but it can be found in British, Dutch, and German sources of the 1960s and 1970s, and throughout the documentation of Philips mainframe computers.

Other Languages
Afrikaans: Greep
Alemannisch: Byte
Ænglisc: Bita
العربية: بايت
অসমীয়া: বাইট
asturianu: Byte
azərbaycanca: Bayt
تۆرکجه: بایت
বাংলা: বাইট
Bân-lâm-gú: Byte
башҡортса: Байт
беларуская: Байт
беларуская (тарашкевіца)‎: Байт
български: Байт
bosanski: Bajt
català: Byte
čeština: Bajt
dansk: Byte
Deutsch: Byte
eesti: Bait
Ελληνικά: Byte
español: Byte
Esperanto: Bajto
euskara: Byte
فارسی: بایت
français: Byte
galego: Byte
한국어: 바이트
հայերեն: Բայթ
हिन्दी: बाइट
hrvatski: Bajt
Bahasa Indonesia: Bita
interlingua: Byte
íslenska: Bæti
italiano: Byte
עברית: בית (מחשב)
Basa Jawa: Bita
ქართული: ბაიტი
қазақша: Байт
Кыргызча: Байт
ລາວ: ໄບຕ໌
latviešu: Baits
Lëtzebuergesch: Byte
lietuvių: Baitas
lumbaart: Byte
magyar: Byte
македонски: Бајт
മലയാളം: ബൈറ്റ്
Bahasa Melayu: Bait
မြန်မာဘာသာ: ဘိုက် (ကွန်ပျူတာ)
Nederlands: Byte
norsk: Byte
norsk nynorsk: Byte i informatikk
occitan: Byte
олык марий: Байт
oʻzbekcha/ўзбекча: Bayt (toʻplam)
ਪੰਜਾਬੀ: ਬਾਈਟ
پنجابی: بائٹ
پښتو: بايټ
polski: Bajt
português: Byte
română: Byte
русский: Байт
Scots: Byte
shqip: Bajti
sicilianu: Byte
Simple English: Byte
slovenčina: Bajt
slovenščina: Bajt
српски / srpski: Бајт
srpskohrvatski / српскохрватски: Bajt
svenska: Byte
தமிழ்: பைட்டு
తెలుగు: బైట్
ไทย: ไบต์
тоҷикӣ: Байт
Türkçe: Bayt
українська: Байт
اردو: بائٹ
Tiếng Việt: Byte
Winaray: Byte
粵語: 字節
中文: 字节