# Byte

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Unit of digital information, usually 8 bits

This article is about the unit of information. For other uses, see [Byte (disambiguation)](/source/Byte_(disambiguation)).

byte Unit system Unit derived from bit Unit of Digital information, data size Symbol B, o (when 8 bits)

The **byte** is a [unit of digital information](/source/Units_of_information) that most commonly consists of eight [bits](/source/Bit). Historically, the byte was the number of bits used to encode a single [character](/source/Character_(computing)) of text in a computer[1][2] and for this reason it is the smallest [addressable](/source/Address_space) unit of [memory](/source/Computer_memory) in many [computer architectures](/source/Computer_architecture). To disambiguate arbitrarily sized bytes from the common [8-bit](/source/8-bit_computing) definition, [network](/source/Computer_network) protocol documents such as the [Internet Protocol](/source/Internet_Protocol) ([RFC](/source/RFC_(identifier)) [791](https://www.rfc-editor.org/rfc/rfc791)) refer to an 8-bit byte as an [octet](/source/Octet_(computing)).[3] Those bits in an octet are usually counted with numbering from 0 to 7 or 7 to 0 depending on the [bit endianness](/source/Bit_numbering).

The size of the byte has historically been [hardware](/source/Computer_hardware)-dependent and no definitive standards existed that mandated the size. Sizes from 1 to 48 bits have been used.[4][5][6][7] The [six-bit character code](/source/Six-bit_character_code) was an often-used implementation in early encoding systems, and computers using six-bit and nine-bit bytes were common in the 1960s. These systems often had [memory words](/source/Word_(computer_architecture)) of 12, 18, 24, 30, 36, 48, or 60 bits, corresponding to 2, 3, 4, 5, 6, 8, or 10 six-bit bytes, and persisted, in legacy systems, into the twenty-first century. In this era, bit groupings in the instruction stream were often referred to as *[syllables](/source/Syllable_(computing))*[a] or *slab*, before the term *byte* became common.

The modern [*de facto* standard](/source/De_facto_standard) of eight bits, as documented in ISO/IEC 2382-1:1993, is a convenient [power of two](/source/Power_of_two) permitting the [binary-encoded](/source/Binary_number) values 0 through 255 for one byte, as 2 to the power of 8 is 256.[8] The international standard [IEC 80000-13](/source/IEC_80000-13) codified this common meaning. Many types of applications use information representable in eight or fewer bits and processor designers commonly optimize for this usage. The popularity of major commercial computing architectures has aided in the ubiquitous acceptance of the 8-bit byte.[9] Modern architectures typically use 32- or 64-bit words, built of four or eight bytes, respectively.

The unit symbol for the byte was designated as the upper-case letter B by the [International Electrotechnical Commission](/source/International_Electrotechnical_Commission) (IEC) and [Institute of Electrical and Electronics Engineers](/source/Institute_of_Electrical_and_Electronics_Engineers) (IEEE).[10] Internationally, the unit *[octet](/source/Octet_(computing))* explicitly defines a sequence of eight bits, eliminating the potential ambiguity of the term "byte".[11][12] The symbol for octet, 'o', also conveniently eliminates the ambiguity in the symbol 'B' between byte and [bel](/source/Decibel).

## Etymology and history

The term *byte* was coined by [Werner Buchholz](/source/Werner_Buchholz) in June 1956,[4][13][14][b] during the early design phase for the [IBM Stretch](/source/IBM_7030)[15][16][1][13][14][17][18] computer, which had addressing to the bit and variable field length (VFL) instructions with a byte size encoded in the instruction.[13] It is a deliberate respelling of *[bite](/source/Bite)* to avoid accidental mutation to *[bit](/source/Bit)*.[1][13][19][c]

Another origin of *byte* for bit groups smaller than a computer's word size, and in particular groups of [four bits](/source/Nibble_(computing)), is on record by Louis G. Dooley, who claimed he coined the term while working with [Jules Schwartz](/source/Jules_Schwartz) and Dick Beeler on an air defense system called [SAGE](/source/Experimental_SAGE_Subsector) at [MIT Lincoln Laboratory](/source/MIT_Lincoln_Laboratory) in 1956 or 1957, which was jointly developed by [Rand](/source/Rand_Corporation), MIT, and IBM.[20][21] Later on, Schwartz's language [JOVIAL](/source/JOVIAL) actually used the term, but the author recalled vaguely that it was derived from [AN/FSQ-31](/source/AN%2FFSQ-31).[22][21]

Early computers used a variety of four-bit [binary-coded decimal](/source/Binary-coded_decimal) (BCD) representations and the [six-bit](/source/Sixbit) codes for printable graphic patterns common in the [U.S. Army](/source/U.S._Army) ([FIELDATA](/source/FIELDATA)) and [Navy](/source/United_States_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](/source/American_Standard_Code_for_Information_Interchange) (ASCII) as the [Federal Information Processing Standard](/source/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](/source/Control_character) 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.[18] During the early 1960s, while also active in ASCII standardization, IBM simultaneously introduced in its product line of [System/360](/source/System%2F360) the eight-bit [Extended Binary Coded Decimal Interchange Code](/source/Extended_Binary_Coded_Decimal_Interchange_Code) (EBCDIC), an expansion of their [six-bit binary-coded decimal](/source/Six-bit_binary-coded_decimal) (BCDIC) representations[d] used in earlier card punches.[23] The prominence of the System/360 led to the ubiquitous adoption of the eight-bit storage size,[18][16][13] while in detail the EBCDIC and ASCII encoding schemes are different.

In the early 1960s, [AT&T](/source/AT%26T) introduced [digital telephony](/source/Digital_telephony) on long-distance [trunk lines](/source/Trunk_line). These used the eight-bit [μ-law encoding](/source/%CE%9C-law_algorithm). This large investment promised to reduce transmission costs for eight-bit data.

In Volume 1 of *[The Art of Computer Programming](/source/The_Art_of_Computer_Programming)* (first published in 1968), [Donald Knuth](/source/Donald_Knuth) uses *byte* in his hypothetical [MIX](/source/MIX_(abstract_machine)) computer to denote a unit which "contains an *unspecified* amount of information ... capable of holding at least 64 distinct values ... *at most* 100 distinct values. On a binary computer a byte must therefore be composed of six bits".[24] He notes that "Since 1975 or so, the word *byte* has come to mean a sequence of precisely eight binary digits...When we speak of bytes in connection with MIX we shall confine ourselves to the former sense of the word, harking back to the days when bytes were not yet standardized."[24]

The development of [eight-bit](/source/Eight-bit) [microprocessors](/source/Microprocessor) in the 1970s popularized this storage size. Microprocessors such as the [Intel 8080](/source/Intel_8080), the direct predecessor of the [8086](/source/Intel_8086), could also perform a small number of operations on the [four-bit](/source/4bit) pairs in a byte, such as the decimal-add-adjust (DAA) instruction. A four-bit quantity is often called a [nibble](/source/Nibble), also *nybble*, which is conveniently represented by a single [hexadecimal](/source/Hexadecimal) digit.

The term *[octet](/source/Octet_(computing))* unambiguously specifies a size of eight bits.[18][12] It is used extensively in [protocol](/source/Protocol_(computing)) definitions.

Historically, the term *octad* or *octade* was used to denote eight bits as well at least in Western Europe;[25][26] 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](/source/Philips) mainframe computers.

## Unit symbol

The unit symbol for the byte is specified in [IEC 80000-13](/source/IEC_80000-13), [IEEE 1541](/source/IEEE_1541) and the [Metric Interchange Format](https://en.wikipedia.org/w/index.php?title=Metric_Interchange_Format&action=edit&redlink=1)[10] as the upper-case character B.

In the [International System of Quantities](/source/International_System_of_Quantities) (ISQ), B is also the symbol of the *[bel](/source/Bel_(acoustics))*, a unit of logarithmic power ratio named after [Alexander Graham Bell](/source/Alexander_Graham_Bell), creating a conflict with the IEC specification. However, little danger of confusion exists, because the bel is a rarely used unit. It is used primarily in its decadic fraction, the [decibel](/source/Decibel) (dB), for [signal strength](/source/Signal_strength) and [sound pressure level](/source/Sound_pressure_level) measurements, while a unit for one-tenth of a byte, the decibyte, and other fractions, are only used in derived units, such as transmission rates.

The lowercase letter o for [octet](/source/Octet_(computing)) is defined as the symbol for octet in IEC 80000-13 and is commonly used in languages such as [French](/source/French_language)[27] and [Romanian](/source/Romanian_language), and is also combined with metric prefixes for multiples, for example ko and Mo.

## Multiple-byte units

"EiB" and "Exabyte" redirect here. For the company, see [Exabyte Corporation](/source/Exabyte_Corporation). For other uses, see [EIB (disambiguation)](/source/EIB_(disambiguation)).

"Zettabytes" redirects here. For the fictional band, see [Zetta Bytes](/source/Zetta_Bytes).

Several terms  redirect here. For other uses, see [Yottabyte (disambiguation)](/source/Yottabyte_(disambiguation)), [KIB (disambiguation)](/source/KIB_(disambiguation)), [MIB (disambiguation)](/source/MIB_(disambiguation)), [GIB (disambiguation)](/source/GIB_(disambiguation)), [TIB (disambiguation)](/source/TIB_(disambiguation)), [PIB (disambiguation)](/source/PIB_(disambiguation)), [Zib (disambiguation)](/source/Zib_(disambiguation)), and [RIB (disambiguation)](/source/RIB_(disambiguation)).

Multiple-byte units v t e Decimal Binary Value SI Value IEC JEDEC 1000 103 kB kilobyte 1024 210 KiB kibibyte KB kilobyte 10002 106 MB megabyte 10242 220 MiB mebibyte MB megabyte 10003 109 GB gigabyte 10243 230 GiB gibibyte GB gigabyte 10004 1012 TB terabyte 10244 240 TiB tebibyte TB terabyte 10005 1015 PB petabyte 10245 250 PiB pebibyte — 10006 1018 EB exabyte 10246 260 EiB exbibyte — 10007 1021 ZB zettabyte 10247 270 ZiB zebibyte — 10008 1024 YB yottabyte 10248 280 YiB yobibyte — 10009 1027 RB ronnabyte 10249 290 RiB robibyte — 100010 1030 QB quettabyte 102410 2100 QiB quebibyte — Orders of magnitude of data

[Unit multiples](/source/Unit_multiple) of the byte are defined in a metric system based on the [powers of 10](/source/Power_of_10), following the [International System of Units](/source/International_System_of_Units) (SI), which defines, for example, the prefix *[kilo](/source/Kilo-)* as 1000 (103), as well as a binary system based on [powers of two](/source/Power_of_two). Historically, the binary system used the identical prefixes of the metric system, but quantified differently. The nomenclature of the latter system has led to confusion. Systems based on powers of 10 use standard [SI prefixes](/source/SI_prefix) (*[kilo](/source/Kilo-)*, *[mega](/source/Mega-)*, *[giga](/source/Giga-)*, ...) and their corresponding symbols (k, M, G, ...). The modern binary system uses prefixes *kibi*, *mebi*, *gibi*, etc., and their corresponding symbols (Ki, Mi, Gi, ...).[e] Historical usage for the binary system still uses the prefixes K, M, and G.

While the difference between the decimal and binary interpretations is relatively small for the kilobyte (about 2% smaller than the kibibyte), the systems deviate increasingly as units grow larger (the relative deviation grows by 2.4% for each three orders of magnitude). For example, a power-of-10-based terabyte is about 9% smaller than power-of-2-based tebibyte.

### Units based on powers of 10 (SI Prefixes)

Definition of prefixes using powers of 10—in which 1 *kilobyte* (symbol kB) is defined to equal 1,000 bytes—is recommended by the International Electrotechnical Commission (IEC).[28] The IEC standard defines eight such multiples, up to 1 yottabyte (YB), equal to 10008 bytes.[29] The additional prefixes *ronna-* for 10009 and *quetta-* for 100010 were adopted by the [International Bureau of Weights and Measures](/source/International_Bureau_of_Weights_and_Measures) (BIPM) in 2022.[30][31]

This definition is most commonly used for [data-rate units](/source/Data-rate_units) in [computer networks](/source/Computer_network), internal bus, hard drive and flash media transfer speeds, [ISP](/source/Internet_service_provider) contracts, and for the capacities of most [storage media](/source/Storage_media), particularly [hard drives](/source/Hard_drive)[32] and [SSDs](/source/Solid-state_drive), [flash](/source/Flash_memory)-based storage,[33] [CDs](/source/Compact_disc), [DVDs](/source/DVD)[34] and [Blu-rays](/source/Blu-ray). [Operating systems](/source/Operating_system) that use this definition include [Android](/source/Android_(operating_system)) (and derivatives), [macOS](/source/MacOS),[35] [iOS](/source/IOS),[35], [WatchOS](/source/WatchOS), [Ubuntu](/source/Ubuntu),[36] and [Debian](/source/Debian)[37], [ChromeOS](/source/ChromeOS), [HarmonyOS](/source/HarmonyOS) and the [Gnome](/source/GNOME) desktop environment. It is also consistent with the other uses of the [SI prefixes](/source/SI_prefix) in computing, such as [CPU clock speeds](/source/Hertz#Computers) or [measures of performance](/source/FLOPS).

The IBM System 360 and the related disk and tape systems set the byte at 8 bits and documented capacities in decimal units.[38] The early 8-, 5.25- and 3.5-inch floppies gave capacities in multiples of 1024, using "KB" rather than the more accurate "KiB". The later, larger, 8-, 5.25- and 3.5-inch floppies gave capacities in a hybrid notation, i.e., multiples of 1024,000, using "KB" = 1024 B and "MB" = 1024,000 B. Early 5.25-inch disks used decimal[*[dubious](https://en.wikipedia.org/wiki/Wikipedia:Accuracy_dispute#Disputed_statement) – [discuss](https://en.wikipedia.org/wiki/Talk:Byte#Units_based_on_powers_of_10)*] even though they used 128-byte and 256-byte sectors.[39] Hard disks used mostly 256-byte and then 512-byte before 4096-byte blocks became standard.[40]

### Units based on powers of 2 (IEC Prefixes)

A system of units based on [powers of 2](/source/Powers_of_2) in which 1 kibibyte (KiB) is equal to 1,024 (i.e., 210) bytes was created by the IEC to solve the confusion over incorrect usage of SI prefixes[41]. It is defined by international standard IEC 80000-13, which is supported by national and international standards bodies ([BIPM](/source/BIPM), [IEC](/source/International_Electrotechnical_Commission), [NIST](/source/NIST)). The IEC standard defines ten such multiples, up to 1 quebibyte (QiB), equal to 102410 bytes.[42] These unit symbols are rarely used in practice.[43] Notable exceptions are [KDE](/source/KDE_Plasma) and applications based on the [Qt toolkit](/source/Qt_(software)) but the KDE settings app allows switching to SI.[44]

A historic convention of nomenclature for the same units, in which 1 *kilobyte* (KB) is equal to 1,024 bytes,[45][46][47] 1 *megabyte* (MB) is equal to 10242 bytes and 1 *gigabyte* (GB) is equal to 10243 bytes is mentioned by a 1990s [JEDEC](/source/JEDEC) standard which is used for [RAM](/source/Random-access_memory). Only the first three multiples (up to GB) are mentioned by the JEDEC standard, which makes no mention of TB and larger. These units can only be recognized through comparison using different software. Sometimes the capitalization of the K in KB can be an indicator. While confusing and incorrect,[48] this convention is used by the [Microsoft Windows](/source/Microsoft_Windows) operating system[49] and [random-access memory](/source/Random-access_memory) capacity, such as main memory and [CPU cache](/source/CPU_cache) size, and in marketing and billing by some telecommunication companies, such as [Vodafone](/source/Vodafone),[50] [AT&T](/source/AT%26T),[51] [Orange](/source/Orange_S.A.)[52] and [Telstra](/source/Telstra).[53] For [storage](/source/Computer_data_storage) capacity, the historic convention was used by macOS and iOS through Mac OS X 10.5 Leopard and iOS 10, after which they switched to units based on powers of 10.[35]

### Parochial units

Various computer vendors have coined terms for data of various sizes, sometimes with different sizes for the same term even within a single vendor. These terms include *double word*, *half word*, *long word*, *quad word*, *slab*, *superword* and *syllable*. There are also informal terms. e.g., *half byte* and *nybble* for 4 bits, *octal K* for 10008.

### History of the conflicting definitions

Percentage difference between decimal and binary interpretations of the unit prefixes grows with increasing storage size

When I see a disk advertised as having a capacity of one megabyte, what is this telling me? There are three plausible answers, and I wonder if anybody knows which one is correct ... Now this is not a really vital issue, as there is just under 5% difference between the smallest and largest alternatives. Nevertheless, it would [be] nice to know what the standard measure is, or if there is one.

— Allan D. Pratt of *Small Computers in Libraries*, 1982[54]

Contemporary[f] computer memory has a [binary architecture](/source/Binary_addressing) making a definition of memory units based on powers of 2 most practical. The use of the metric prefix *kilo* for binary multiples arose as a convenience, because 1024 is approximately 1000.[27] This definition was popular in early decades of [personal computing](/source/Personal_computing), with products like the [Tandon](/source/Tandon_Corporation) 51⁄4-inch [DD](/source/Double_density) floppy format (holding 368640 bytes) being advertised as "360 KB", following the 1024-byte convention. It was not universal, however. The [Shugart](/source/Shugart_Associates) SA-400 51⁄4-inch [floppy disk](/source/Floppy_disk) held 109,375 bytes unformatted,[55] and was advertised as "110 Kbyte", using the 1000 convention.[56] Likewise, the 8-inch [DEC](/source/Digital_Equipment_Corporation) RX01 floppy (1975) held 256256 bytes formatted, and was advertised as "256k".[57] Some devices were advertised using a *mixture* of the two definitions: most notably, floppy disks advertised as "1.44 MB" have an actual capacity of 1440 KiB, the equivalent of 1.47 MB or 1.41 MiB.

In 1995, the [International Union of Pure and Applied Chemistry](/source/International_Union_of_Pure_and_Applied_Chemistry)'s (IUPAC) Interdivisional Committee on Nomenclature and Symbols attempted to resolve this ambiguity by proposing a set of [binary prefixes](/source/Binary_prefixes) for the powers of 1024, including kibi (kilobinary), mebi (megabinary), and gibi (gigabinary).[58][59]

In December 1998, the [IEC](/source/International_Electrotechnical_Commission) addressed such multiple usages and definitions by adopting the IUPAC's proposed prefixes (kibi, mebi, gibi, etc.) to unambiguously denote powers of 1024.[60] Thus one kibibyte (1 KiB) is 10241 bytes = 1024 bytes, one mebibyte (1 MiB) is 10242 bytes = 1048576 bytes, and so on.

In 1999, [Donald Knuth](/source/Donald_Knuth) suggested calling the kibibyte a "large kilobyte" (*KKB*).[61]

### Modern standard definitions

The IEC adopted the IUPAC proposal and published the standard in January 1999.[62][63] The IEC prefixes are part of the [International System of Quantities](/source/IEC_80000-13). The IEC further specified that the kilobyte should only be used to refer to 1000 bytes.[64]

### Lawsuits over definition

Lawsuits arising from alleged consumer confusion over the binary and decimal definitions of multiples of the byte have generally ended in favor of the manufacturers, with courts holding that the legal definition of gigabyte or GB is 1 GB = 1000000000 (109) bytes (the decimal definition), rather than the binary definition (230, i.e., 1073741824). Specifically, the United States District Court for the Northern District of California held that "the U.S. Congress has deemed the decimal definition of gigabyte to be the 'preferred' one for the purposes of 'U.S. trade and commerce' [...] The California Legislature has likewise adopted the decimal system for all 'transactions in this state.'"[65]

Earlier lawsuits had ended in settlement with no court ruling on the question, such as a lawsuit against drive manufacturer [Western Digital](/source/Western_Digital).[66][67] Western Digital settled the challenge and added explicit disclaimers to products that the usable capacity may differ from the advertised capacity.[66] Seagate was sued on similar grounds and also settled.[66][68]

### Practical examples

Unit Approximate equivalent bit a Boolean variable indicating true (1) or false (0) byte a basic Latin character. kilobyte text of "Jabberwocky" a typical favicon megabyte text of Harry Potter and the Goblet of Fire[69] gigabyte about 20 minutes of video on a 4.7 GB DVD 1½ standard CDs terabyte the largest consumer hard drive in 2007[70] 20 standard Blu-rays or 213 DVDs petabyte 2000 years of MP3-encoded music[71] exabyte global monthly Internet traffic in 2004[72] zettabyte global yearly Internet traffic in 2016 (known as the Zettabyte Era)[73]

## Common uses

Many [programming languages](/source/Programming_language) define the [data type](/source/Data_type) *byte*.

[Java](/source/Java_(programming_language))[74], [.NET](/source/.NET) ([C#](/source/C_Sharp_(programming_language)), [F#](/source/F_Sharp_(programming_language)), [VB.NET](/source/Visual_Basic_(.NET)))[75], [Rust](/source/Rust_(programming_language))[76], [D](/source/D_(programming_language))[77], [Go](/source/Go_(programming_language))[78], [Swift](/source/Swift_(programming_language))[79], [JavaScript](/source/JavaScript)[80], [Python](/source/Python_(programming_language))[81], [Ruby](/source/Ruby_(programming_language)) all define and use 8-bit bytes capable of holding exactly 256 different values.

The [C](/source/C_(programming_language)) and [C++](/source/C%2B%2B) programming languages define *byte* as an "addressable unit of data storage large enough to hold any member of the basic character set of the execution environment" (clause 3.6 of the C standard). The C standard requires that the integral data type *[unsigned](/source/Signedness) char* must hold at least 256 different values, and is represented by at least eight bits (clause 5.2.4.2.1). Various implementations of C and C++ reserve 8, 9, 16, 32, or 36 bits for the storage of a byte.[82][83][g] In addition, the C and C++ standards require that there be no gaps between two bytes. This means every bit in memory is part of a byte.[84] In [C++17](/source/C%2B%2B17), a std::byte [enumerated type](/source/Enumerated_type) was introduced with underlying representation as unsigned char, which is used to model a collection of bits and is not an arithmetic or character type. It is defined as an enum to prevent arithmetic use, but has no defined constants (instead being used like byte x{0xFF};).[85]

However almost all modern software would not actually work if compiled with a byte size other than 8 bit. Further [POSIX](/source/POSIX) says "A byte is composed of a contiguous sequence of 8 bits."[86] Today, non-8-bit bytes only find niche application like in [DSPs](/source/Digital_signal_processor).

In data transmission systems, the byte is used as a contiguous sequence of bits in a serial data stream, representing the smallest distinguished unit of data. For [asynchronous communication](/source/Asynchronous_communication) a full transmission unit usually additionally includes a start bit, 1 or 2 stop bits, and possibly a [parity bit](/source/Parity_bit), and thus its size may vary from seven to twelve bits for five to eight bits of actual data.[87] For [synchronous communication](/source/Synchronous_communication) the error checking usually uses bytes at the end of a [frame](/source/Frame_(networking)).

## See also

- [Data](/source/Data)

- [Data hierarchy](/source/Data_hierarchy)

- [Nibble](/source/Nibble)

- [Octet (computing)](/source/Octet_(computing))

- [Primitive data type](/source/Primitive_data_type)

- [Tryte](/source/Tryte)

- [Word (computer architecture)](/source/Word_(computer_architecture))

## Notes

1. **[^](#cite_ref-8)** The term syllable was used for bytes containing instructions or constituents of instructions, not for data bytes.

1. **[^](#cite_ref-16)** Many sources erroneously indicate a birthday of the term *byte* in July 1956, but [Werner Buchholz](/source/Werner_Buchholz) claimed that the term would have been coined in [June 1956](#Buchholz-1977). In fact, the [earliest document](#Buchholz-1956-1) supporting this dates from 1956-06-11. Buchholz stated that the transition to 8-bit bytes was conceived in [August 1956](#Buchholz-1977), but the earliest document found using this notion dates from [September 1956](#Buchholz-1956-3).

1. **[^](#cite_ref-22)** Some later machines, e.g., [Burroughs B1700](/source/Burroughs_B1700), [CDC 3600](/source/CDC_3600), DEC PDP-6, [DEC PDP-10](/source/DEC_PDP-10) had the ability to operate on arbitrary bytes no larger than the word size.

1. **[^](#cite_ref-26)** There was more than one BCD code page.

1. **[^](#cite_ref-32)** The IEC prefix symbols are made by appending the letter "i" to the corresponding SI symbols, except for "Ki" which also has a change of initial case compared to the lowercase "k".

1. **[^](#cite_ref-60)** Through the 1970s there were machines with [decimal](/source/Decimal_computer) architectures.

1. **[^](#cite_ref-90)** The actual number of bits in a particular implementation is documented as CHAR_BIT as implemented in the file [limits.h](/source/Limits.h).

## References

1. ^ [***a***](#cite_ref-Buchholz_1962_1-0) [***b***](#cite_ref-Buchholz_1962_1-1) [***c***](#cite_ref-Buchholz_1962_1-2) [Blaauw, Gerrit Anne](/source/Gerrit_Anne_Blaauw); [Brooks, Jr., Frederick Phillips](/source/Frederick_Phillips_Brooks%2C_Jr.); [Buchholz, Werner](/source/Werner_Buchholz) (1962), ["Chapter 4: Natural Data Units"](https://web.archive.org/web/20170403014651/http://archive.computerhistory.org/resources/text/IBM/Stretch/pdfs/Buchholz_102636426.pdf) (PDF), in [Buchholz, Werner](/source/Werner_Buchholz) (ed.), *Planning a Computer System - Project Stretch*, [McGraw-Hill Book Company, Inc.](/source/McGraw-Hill_Book_Company%2C_Inc.) / The Maple Press Company, York, PA., pp. 39–40, [LCCN](/source/LCCN_(identifier)) [61-10466](https://lccn.loc.gov/61-10466), archived from [the original](http://archive.computerhistory.org/resources/text/IBM/Stretch/pdfs/Buchholz_102636426.pdf) (PDF) on 2017-04-03, retrieved 2017-04-03 Terms used here to describe the structure imposed by the machine design, in addition to *[bit](/source/Bit)*, are listed below. *Byte* denotes a group of bits used to encode a character, or the number of bits transmitted in parallel to and from input-output units. A term other than *[character](/source/Character_(computing))* is used here because a given character may be represented in different applications by more than one code, and different codes may use different numbers of bits (i.e., different byte sizes). In input-output transmission the grouping of bits may be completely arbitrary and have no relation to actual characters. (The term is coined from *[bite](/source/Bite)*, but respelled to avoid accidental mutation to *bit*.) A *[word](/source/Word_(unit))* consists of the number of data bits transmitted in parallel from or to memory in one memory cycle. [Word size](/source/Word_size) is thus defined as a structural property of the memory. (The term *[catena](/source/Catena_(unit))* was coined for this purpose by the designers of the [Bull](/source/Groupe_Bull) [GAMMA 60](/source/Bull_Gamma_60) [[fr](https://fr.wikipedia.org/wiki/Gamma_60)] computer.) *[Block](/source/Block_(data_storage))* refers to the number of words transmitted to or from an input-output unit in response to a single input-output instruction. Block size is a structural property of an input-output unit; it may have been fixed by the design or left to be varied by the program.

1. **[^](#cite_ref-Bemer_1959_2-0)** [Bemer, Robert William](/source/Robert_William_Bemer) (1959), "A proposal for a generalized card code of 256 characters", *[Communications of the ACM](/source/Communications_of_the_ACM)*, **2** (9): 19–23, [doi](/source/Doi_(identifier)):[10.1145/368424.368435](https://doi.org/10.1145%2F368424.368435), [S2CID](/source/S2CID_(identifier)) [36115735](https://api.semanticscholar.org/CorpusID:36115735)

1. **[^](#cite_ref-3)** [Postel, J.](/source/Jon_Postel) (September 1981). [*Internet Protocol DARPA INTERNET PROGRAM PROTOCOL SPECIFICATION*](https://www.rfc-editor.org/rfc/rfc791#page-43). [IETF](/source/Internet_Engineering_Task_Force). p. 43. [doi](/source/Doi_(identifier)):[10.17487/RFC0791](https://doi.org/10.17487%2FRFC0791). [RFC](/source/Request_for_Comments) [791](https://datatracker.ietf.org/doc/html/rfc791). Retrieved 28 August 2020. octet An eight bit byte.

1. ^ [***a***](#cite_ref-Buchholz_1956_1_4-0) [***b***](#cite_ref-Buchholz_1956_1_4-1) [Buchholz, Werner](/source/Werner_Buchholz) (1956-06-11). ["7. The Shift Matrix"](https://web.archive.org/web/20170404152534/http://archive.computerhistory.org/resources/text/IBM/Stretch/pdfs/06-07/102632284.pdf) (PDF). *The Link System*. [IBM](/source/IBM). pp. 5–6. [Stretch](/source/IBM_Stretch) Memo No. 39G. Archived from [the original](http://archive.computerhistory.org/resources/text/IBM/Stretch/pdfs/06-07/102632284.pdf) (PDF) on 2017-04-04. Retrieved 2016-04-04. [...] Most important, from the point of view of editing, will be the ability to handle any characters or digits, from 1 to 6 bits long. Figure 2 shows the Shift Matrix to be used to convert a 60-bit [word](/source/Word_(computer_architecture)), coming from Memory in parallel, into [characters](/source/Character_(computing)), or 'bytes' as we have called them, to be sent to the [Adder](/source/Serial_adder) serially. The 60 bits are dumped into [magnetic cores](/source/Magnetic_core) on six different levels. Thus, if a 1 comes out of position 9, it appears in all six cores underneath. Pulsing any diagonal line will send the six bits stored along that line to the Adder. The Adder may accept all or only some of the bits. Assume that it is desired to operate on 4 bit [decimal digits](/source/Decimal_digit), starting at the right. The 0-diagonal is pulsed first, sending out the six bits 0 to 5, of which the Adder accepts only the first four (0-3). Bits 4 and 5 are ignored. Next, the 4 diagonal is pulsed. This sends out bits 4 to 9, of which the last two are again ignored, and so on. It is just as easy to use all six bits in [alphanumeric](/source/Alphanumeric) work, or to handle bytes of only one bit for logical analysis, or to offset the bytes by any number of bits. All this can be done by pulling the appropriate shift diagonals. An analogous matrix arrangement is used to change from serial to parallel operation at the output of the adder. [...]

1. **[^](#cite_ref-CDC_1965_3600_5-0)** [*3600 Computer System - Reference Manual*](https://web.archive.org/web/20170405154001/http://bitsavers.informatik.uni-stuttgart.de/pdf/cdc/3x00/48bit/60021300K_3600_SysRef_Oct66.pdf) (PDF). K. St. Paul, Minnesota, US: [Control Data Corporation](/source/Control_Data_Corporation) (CDC). 1966-10-11 [1965]. 60021300. Archived from [the original](http://bitsavers.org/pdf/cdc/3x00/48bit/60021300K_3600_SysRef_Oct66.pdf) (PDF) on 2017-04-05. Retrieved 2017-04-05. Byte - A partition of a computer word. NB. Discusses 12-bit, 24-bit and 48-bit bytes.

1. **[^](#cite_ref-Rao_1989_6-0)** Rao, Thammavaram R. N.; Fujiwara, Eiji (1989). McCluskey, Edward J. (ed.). [*Error-Control Coding for Computer Systems*](https://archive.org/details/errorcontrolcodi00unse). Prentice Hall Series in Computer Engineering (1 ed.). Englewood Cliffs, NJ, US: [Prentice Hall](/source/Prentice_Hall). [ISBN](/source/ISBN_(identifier)) [0-13-283953-9](https://en.wikipedia.org/wiki/Special:BookSources/0-13-283953-9). [LCCN](/source/LCCN_(identifier)) [88-17892](https://lccn.loc.gov/88-17892). NB. Example of the usage of a code for "4-bit bytes".

1. **[^](#cite_ref-Tafel_1971_7-0)** Tafel, Hans Jörg (1971). *Einführung in die digitale Datenverarbeitung* [*Introduction to digital information processing*] (in German). Munich: [Carl Hanser Verlag](/source/Carl_Hanser_Verlag). p. 300. [ISBN](/source/ISBN_(identifier)) [3-446-10569-7](https://en.wikipedia.org/wiki/Special:BookSources/3-446-10569-7). Byte = zusammengehörige Folge von i.a. neun Bits; davon sind acht Datenbits, das neunte ein Prüfbit NB. Defines a byte as a group of typically 9 bits; 8 data bits plus 1 parity bit.

1. **[^](#cite_ref-ISO_IEC_2382-1_1993_9-0)** *ISO/IEC 2382-1: 1993, Information technology - Vocabulary - Part 1: Fundamental terms*. 1993. byte: A string that consists of a number of bits, treated as a unit, and usually representing a character or a part of a character. NOTES: 1 The number of bits in a byte is fixed for a given data processing system. 2 The number of bits in a byte is usually 8.

1. **[^](#cite_ref-CHM_1964_10-0)** ["Internet History of 1960s # 1964"](https://www.computerhistory.org/internethistory/1960s/#1964). [Computer History Museum](/source/Computer_History_Museum). 2017 [2015]. [Archived](https://web.archive.org/web/20220624184757/https://www.computerhistory.org/internethistory/1960s/#1964) from the original on 2022-06-24. Retrieved 2022-08-17.

1. ^ [***a***](#cite_ref-MIXF_11-0) [***b***](#cite_ref-MIXF_11-1) [Jaffer, Aubrey](https://en.wikipedia.org/w/index.php?title=Aubrey_Jaffer&action=edit&redlink=1) (2011) [2008]. ["Metric-Interchange-Format"](https://people.csail.mit.edu/jaffer/MIXF/). [Archived](https://web.archive.org/web/20170403121705/https://people.csail.mit.edu/jaffer/MIXF/) from the original on 2017-04-03. Retrieved 2017-04-03.

1. **[^](#cite_ref-TCPIP_12-0)** Kozierok, Charles M. (2005-09-20) [2001]. ["The TCP/IP Guide - Binary Information and Representation: Bits, Bytes, Nibbles, Octets and Characters - Byte versus Octet"](http://www.tcpipguide.com/free/t_BinaryInformationandRepresentationBitsBytesNibbles-3.htm). 3.0. [Archived](https://web.archive.org/web/20170403122042/http://www.tcpipguide.com/free/t_BinaryInformationandRepresentationBitsBytesNibbles-3.htm) from the original on 2017-04-03. Retrieved 2017-04-03.

1. ^ [***a***](#cite_ref-ISO_2382-4_13-0) [***b***](#cite_ref-ISO_2382-4_13-1) *ISO 2382-4, Organization of data* (2 ed.). byte, octet, 8-bit byte: A string that consists of eight bits.

1. ^ [***a***](#cite_ref-Buchholz_1977_14-0) [***b***](#cite_ref-Buchholz_1977_14-1) [***c***](#cite_ref-Buchholz_1977_14-2) [***d***](#cite_ref-Buchholz_1977_14-3) [***e***](#cite_ref-Buchholz_1977_14-4) [Buchholz, Werner](/source/Werner_Buchholz) (February 1977). ["The Word "Byte" Comes of Age..."](https://archive.org/details/byte-magazine-1977-02/page/n145/mode/1up) *[Byte Magazine](/source/Byte_Magazine)*. **2** (2): 144. *We received the following from W Buchholz, one of the individuals who was working on IBM's Project Stretch in the mid 1950s. His letter tells the story.* Not being a regular reader of your magazine, I heard about the question in the November 1976 issue regarding the origin of the term "byte" from a colleague who knew that I had perpetrated this piece of jargon *[see page 77 of November 1976 BYTE, "Olde Englishe"]*. I searched my files and could not locate a birth certificate. But I am sure that "byte" is coming of age in 1977 with its 21st birthday. Many have assumed that byte, meaning 8 bits, originated with the IBM System/360, which spread such bytes far and wide in the mid-1960s. The editor is correct in pointing out that the term goes back to the earlier Stretch computer (but incorrect in that Stretch was the first, not the last, of IBM's second-generation transistorized computers to be developed). The first reference found in the files was contained in an internal memo written in June 1956 during the early days of developing [Stretch](/source/IBM_Stretch). A byte was described as consisting of any number of parallel bits from one to six. Thus a byte was assumed to have a length appropriate for the occasion. Its first use was in the context of the input-output equipment of the 1950s, which handled six bits at a time. The possibility of going to 8-bit bytes was considered in [August 1956](#Note-Dates) and incorporated in the design of Stretch [shortly thereafter](#Buchholz-1956-3). The first published reference to the term occurred in 1959 in a paper '[Processing Data in Bits and Pieces](#Blaauw-1959)' by [G A Blaauw](/source/Gerrit_Anne_Blaauw), [F P Brooks Jr](/source/Frederick_Phillips_Brooks%2C_Jr.) and [W Buchholz](/source/Werner_Buchholz) in the *[IRE Transactions on Electronic Computers](/source/IRE_Transactions_on_Electronic_Computers)*, June 1959, page 121. The notions of that paper were elaborated in [Chapter 4 of *Planning a Computer System (Project Stretch)*](#Buchholz-1962), edited by W Buchholz, McGraw-Hill Book Company (1962). The rationale for coining the term was explained there on page 40 as follows: Byte *denotes a group of bits used to encode a character, or the number of bits transmitted in parallel to and from input-output units. A term other than* character *is used here because a given character may be represented in different applications by more than one code, and different codes may use different numbers of bits (ie, different byte sizes). In input-output transmission the grouping of bits may be completely arbitrary and have no relation to actual characters. (The term is coined from* [bite](/source/Bite), *but respelled to avoid accidental mutation to* bit.*)* [System/360](/source/System%2F360) took over many of the Stretch concepts, including the basic byte and word sizes, which are powers of 2. For economy, however, the byte size was fixed at the 8 bit maximum, and addressing at the bit level was replaced by byte addressing. Since then the term byte has generally meant 8 bits, and it has thus passed into the general vocabulary. Are there any other terms coined especially for the computer field which have found their way into general dictionaries of English language?

1. ^ [***a***](#cite_ref-Timeline_1956_15-0) [***b***](#cite_ref-Timeline_1956_15-1) ["Timeline of the IBM Stretch/Harvest era (1956-1961)"](https://web.archive.org/web/20160429212717/http://archive.computerhistory.org/resources/text/IBM/Stretch/102636400.txt). [Computer History Museum](/source/Computer_History_Museum). June 1956. Archived from [the original](http://archive.computerhistory.org/resources/text/IBM/Stretch/102636400.txt) on 2016-04-29. Retrieved 2017-04-03. 1956 Summer: [Gerrit Blaauw](/source/Gerrit_Blaauw), [Fred Brooks](/source/Fred_Brooks), [Werner Buchholz](/source/Werner_Buchholz), [John Cocke](/source/John_Cocke_(computer_scientist)) and Jim Pomerene join the [Stretch](/source/IBM_Stretch) team. Lloyd Hunter provides [transistor](/source/Transistor) leadership. 1956 July [*[sic](/source/Sic)*]: In a report Werner Buchholz lists the advantages of a 64-bit word length for Stretch. It also supports [NSA](/source/NSA)'s requirement for 8-bit bytes. Werner's term "Byte" first popularized in this memo. NB. This timeline erroneously specifies the birth date of the term "byte" as *[July 1956](#Note-Dates)*, while Buchholz actually used the term as early as *[June 1956](#Buchholz-1956-1)*.

1. **[^](#cite_ref-Buchholz_1956_2_17-0)** [Buchholz, Werner](/source/Werner_Buchholz) (1956-07-31). ["5. Input-Output"](https://web.archive.org/web/20170404160423/http://archive.computerhistory.org/resources/text/IBM/Stretch/pdfs/06-08/102632289.pdf) (PDF). *Memory Word Length*. [IBM](/source/IBM). p. 2. [Stretch](/source/IBM_Stretch) Memo No. 40. Archived from [the original](http://archive.computerhistory.org/resources/text/IBM/Stretch/pdfs/06-08/102632289.pdf) (PDF) on 2017-04-04. Retrieved 2016-04-04. [...] 60 is a multiple of 1, 2, 3, 4, 5, and 6. Hence bytes of length from 1 to 6 bits can be packed efficiently into a 60-bit [word](/source/Word_(computer_architecture)) without having to split a byte between one word and the next. If longer bytes were needed, 60 bits would, of course, no longer be ideal. With present applications, 1, 4, and 6 bits are the really important cases. With 64-bit words, it would often be necessary to make some compromises, such as leaving 4 bits unused in a word when dealing with 6-bit bytes at the input and output. However, the LINK Computer can be equipped to edit out these gaps and to permit handling of bytes which are split between words. [...]

1. ^ [***a***](#cite_ref-Buchholz_1956_3_18-0) [***b***](#cite_ref-Buchholz_1956_3_18-1) [Buchholz, Werner](/source/Werner_Buchholz) (1956-09-19). ["2. Input-Output Byte Size"](https://web.archive.org/web/20170404161611/http://archive.computerhistory.org/resources/text/IBM/Stretch/pdfs/06-08/102632292.pdf) (PDF). *Memory Word Length and Indexing*. [IBM](/source/IBM). p. 1. [Stretch](/source/IBM_Stretch) Memo No. 45. Archived from [the original](http://archive.computerhistory.org/resources/text/IBM/Stretch/pdfs/06-08/102632292.pdf) (PDF) on 2017-04-04. Retrieved 2016-04-04. [...] The maximum input-output byte size for serial operation will now be 8 bits, not counting any error detection and correction bits. Thus, the Exchange will operate on an 8-bit byte basis, and any input-output units with less than 8 bits per byte will leave the remaining bits blank. The resultant gaps can be edited out later by programming [...]

1. **[^](#cite_ref-ESR_19-0)** [Raymond, Eric Steven](/source/Eric_Steven_Raymond) (2017) [2003]. ["byte definition"](http://catb.org/~esr/jargon/html/B/byte.html). [Archived](https://web.archive.org/web/20170403120304/http://catb.org/~esr/jargon/html/B/byte.html) from the original on 2017-04-03. Retrieved 2017-04-03.

1. ^ [***a***](#cite_ref-Bemer_2000_20-0) [***b***](#cite_ref-Bemer_2000_20-1) [***c***](#cite_ref-Bemer_2000_20-2) [***d***](#cite_ref-Bemer_2000_20-3) [Bemer, Robert William](/source/Robert_William_Bemer) (2000-08-08). ["Why is a byte 8 bits? Or is it?"](https://web.archive.org/web/20170403130829/http://www.bobbemer.com/BYTE.HTM). *Computer History Vignettes*. Archived from [the original](http://www.bobbemer.com/BYTE.HTM) on 2017-04-03. Retrieved 2017-04-03. I came to work for [IBM](/source/IBM), and saw all the confusion caused by the 64-character limitation. Especially when we started to think about word processing, which would require both upper and lower case. *Add 26 lower case letters to 47 existing, and one got 73 -- 9 more than 6 bits could represent.* I even made a proposal (in view of [STRETCH](/source/IBM_Stretch), the very first computer I know of with an 8-bit byte) that would extend the number of [punch card](/source/Punch_card) character codes to 256 [\[1\]](#Bemer_1959). *Some folks took it seriously. I thought of it as a spoof.* So some folks started thinking about 7-bit characters, but this was ridiculous. With IBM's STRETCH computer as background, handling 64-character words divisible into groups of 8 (I designed the character set for it, under the guidance of Dr. [Werner Buchholz](/source/Werner_Buchholz), the man who DID coin the term "byte" for an 8-bit grouping). [2] It seemed reasonable to make a universal 8-bit character set, handling up to 256. In those days my mantra was "powers of 2 are magic". And so the group I headed developed and justified such a proposal [3]. *That was a little too much progress when presented to the standards group that was to formalize ASCII, so they stopped short for the moment with a 7-bit set, or else an 8-bit set with the upper half left for future work.* The [IBM 360](/source/IBM_System_360) used 8-bit characters, although not ASCII directly. Thus Buchholz's "byte" caught on everywhere. I myself did not like the name for many reasons. The design had 8 bits moving around in parallel. But then came a new IBM part, with 9 bits for self-checking, both inside the CPU and in the [tape drives](/source/Tape_drive). I exposed this 9-bit byte to the press in 1973. But long before that, when I headed software operations for [Cie. Bull](/source/Cie._Bull) in France in 1965-66, I insisted that 'byte' be deprecated in favor of "[octet](/source/Octet_(computing))". *You can notice that my preference then is now the preferred term.* It is justified by new communications methods that can carry 16, 32, 64, and even 128 bits in parallel. But some foolish people now refer to a "16-bit byte" because of this parallel transfer, which is visible in the [UNICODE](/source/UNICODE) set. I'm not sure, but maybe this should be called a "[hextet](/source/Hextet)". *But you will notice that I am still correct. Powers of 2 are still magic!*

1. **[^](#cite_ref-Blaauw_1959_21-0)** [Blaauw, Gerrit Anne](/source/Gerrit_Anne_Blaauw); [Brooks, Jr., Frederick Phillips](/source/Frederick_Phillips_Brooks%2C_Jr.); [Buchholz, Werner](/source/Werner_Buchholz) (June 1959). "Processing Data in Bits and Pieces". *[IRE Transactions on Electronic Computers](/source/IRE_Transactions_on_Electronic_Computers)*: 121.

1. **[^](#cite_ref-Dooley_1995_Byte_23-0)** Dooley, Louis G. (February 1995). ["Byte: The Word"](https://web.archive.org/web/19961220122258/http://www.byte.com/art/9502/sec2/art12.htm). *[BYTE](/source/BYTE)*. Ocala, FL, US. Archived from [the original](http://www.byte.com/art/9502/sec2/art12.htm) on 1996-12-20. The word byte was coined around 1956 to 1957 at [MIT Lincoln Laboratories](/source/MIT_Lincoln_Laboratory) within a project called [SAGE](/source/Experimental_SAGE_Subsector) (the North American Air Defense System), which was jointly developed by [Rand](/source/Rand_Corporation), Lincoln Labs, and [IBM](/source/IBM). In that era, computer memory structure was already defined in terms of [word size](/source/Word_size_(computing)). A word consisted of x number of [bits](/source/Bit); a bit represented a binary notational position in a word. Operations typically operated on all the bits in the full word. We coined the word byte to refer to a logical set of bits less than a full word size. At that time, it was not defined specifically as x bits but typically referred to as a set of [4 bits](/source/Nibble_(computing)), as that was the size of most of our coded data items. Shortly afterward, I went on to other responsibilities that removed me from SAGE. After having spent many years in Asia, I returned to the U.S. and was bemused to find out that the word byte was being used in the new microcomputer technology to refer to the basic addressable memory unit.

1. ^ [***a***](#cite_ref-Ram_Byte_24-0) [***b***](#cite_ref-Ram_Byte_24-1) Ram, Stefan (17 January 2003). ["Erklärung des Wortes "Byte" im Rahmen der Lehre binärer Codes"](http://userpage.fu-berlin.de/~ram/pub/pub_jf47ht81Ht/code_byte_de) (in German). Berlin, Germany: [Freie Universität Berlin](/source/Freie_Universit%C3%A4t_Berlin). [Archived](https://web.archive.org/web/20210610055304/http://userpage.fu-berlin.de/~ram/pub/pub_jf47ht81Ht/code_byte_de) from the original on 2021-06-10. Retrieved 2017-04-10.

1. **[^](#cite_ref-Schwartz_Brooks_ACM_25-0)** [*Origin of the term "byte", 1956*](http://www.xent.com/FoRK-archive/july99/0646.html), [archived](https://web.archive.org/web/20170410125522/http://www.xent.com/FoRK-archive/july99/0646.html) from the original on 2017-04-10, retrieved 2022-08-17 A question-and-answer session at an [ACM conference](/source/ACM_conference) on the history of programming languages included this exchange: [ [John Goodenough](/source/John_Goodenough): You mentioned that the term "byte" is used in [JOVIAL](/source/JOVIAL). Where did the term come from? ] [ [Jules Schwartz](/source/Jules_Schwartz) (inventor of JOVIAL): As I recall, the [AN/FSQ-31](/source/AN%2FFSQ-31), a totally different computer than the [709](/source/IBM_709), was byte oriented. I don't recall for sure, but I'm reasonably certain the description of that computer included the word "byte," and we used it. ] [ [Fred Brooks](/source/Fred_Brooks): May I speak to that? [Werner Buchholz](/source/Werner_Buchholz) coined the word as part of the definition of [STRETCH](/source/IBM_STRETCH), and the AN/FSQ-31 picked it up from STRETCH, but Werner is very definitely the author of that word. ] [ Schwartz: That's right. Thank you. ]

1. **[^](#cite_ref-ibm.com_27-0)** ["List of EBCDIC codes by IBM"](https://www.ibm.com/support/knowledgecenter/SSGH4D_16.1.0/com.ibm.xlf161.aix.doc/language_ref/asciit.html). *ibm.com*. 2020-01-02. [Archived](https://web.archive.org/web/20200703073611/https://www.ibm.com/support/knowledgecenter/SSGH4D_16.1.0/com.ibm.xlf161.aix.doc/language_ref/asciit.html) from the original on 2020-07-03. Retrieved 2020-07-03.

1. ^ [***a***](#cite_ref-Knuth-1_28-0) [***b***](#cite_ref-Knuth-1_28-1) Knuth, Donald (1997) [1968]. *The Art of Computer Programming: Volume 1: Fundamental Algorithms* (3rd ed.). Boston: Addison-Wesley. p. 125. [ISBN](/source/ISBN_(identifier)) [9780201896831](https://en.wikipedia.org/wiki/Special:BookSources/9780201896831).

1. **[^](#cite_ref-Williams_1969_29-0)** Williams, R. H. (1969). *British Commercial Computer Digest: Pergamon Computer Data Series*. [Pergamon Press](/source/Pergamon_Press). [ISBN](/source/ISBN_(identifier)) [1483122107](https://en.wikipedia.org/wiki/Special:BookSources/1483122107). [ISBN](/source/ISBN_(identifier)) [978-1483122106](https://en.wikipedia.org/wiki/Special:BookSources/978-1483122106)[*[page needed](https://en.wikipedia.org/wiki/Wikipedia:Citing_sources)*][*[clarification needed](https://en.wikipedia.org/wiki/Wikipedia:Please_clarify)*]

1. **[^](#cite_ref-Philips_1971_30-0)** ["Philips Data Systems' product range"](https://web.archive.org/web/20160304072023/http://www.intact-reunies.nl/pdf/product1971.pdf) (PDF). [Philips](/source/Philips). April 1971. Archived from the original on 2016-03-04. Retrieved 2015-08-03.

1. ^ [***a***](#cite_ref-IEC_Binary_31-0) [***b***](#cite_ref-IEC_Binary_31-1) [ |*| About bits and bytes: prefixes for binary multiples - IEC |*| v0: [https://web.archive.org/web/20090818042050/http://www.iec.ch/online_news/etech/arch_2003/etech_0503/focus.htm](https://web.archive.org/web/20090818042050/http://www.iec.ch/online_news/etech/arch_2003/etech_0503/focus.htm) |*| v1: [https://www.iec.ch/prefixes-binary-multiples](https://www.iec.ch/prefixes-binary-multiples) [Archived](https://web.archive.org/web/20210816011633/https://www.iec.ch/prefixes-binary-multiples) 2021-08-16 at the [Wayback Machine](/source/Wayback_Machine) ]

1. **[^](#cite_ref-NIST_33-0)** [Prefixes for Binary Multiples](http://physics.nist.gov/cuu/Units/binary.html) [Archived](https://web.archive.org/web/20070808000831/http://physics.nist.gov/cuu/Units/binary.html) 2007-08-08 at the [Wayback Machine](/source/Wayback_Machine) — The NIST Reference on Constants, Units, and Uncertainty

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## Further reading

- ["2.5 Byte manipulation"](http://bitsavers.org/pdf/dec/pdp10/1970_PDP-10_Ref/1970PDP10Ref_Part1.pdf#page=33) (PDF). [*Programming with the PDP-10 Instruction Set*](http://bitsavers.org/pdf/dec/pdp10/1970_PDP-10_Ref/1970PDP10Ref_Part1.pdf) (PDF). PDP-10 System Reference Manual. Vol. 1. [Digital Equipment Corporation](/source/Digital_Equipment_Corporation) (DEC). August 1969. pp. 2-15 – 2-17. [Archived](https://web.archive.org/web/20170405154620/http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/pdp10/1970_PDP-10_Ref/1970PDP10Ref_Part1.pdf) (PDF) from the original on 2017-04-05. Retrieved 2017-04-05.

- Ashley Taylor. "Bits and Bytes". Stanford. [https://web.stanford.edu/class/cs101/bits-bytes.html](https://web.stanford.edu/class/cs101/bits-bytes.html)

v t e Units of information Platform-independent units bit hextet octet Platform-dependent units nibble byte syllable word Metric bit units kilobit megabit Metric byte units kilobyte megabyte gigabyte

v t e Data types Uninterpreted Bit Byte Trit Tryte Word Bit array Numeric Arbitrary-precision or bignum Complex Decimal Fixed point Block floating point Floating point Reduced precision Minifloat Half precision bfloat16 Single precision Double precision Quadruple precision Octuple precision Extended precision Long double Integer signedness Interval Rational Reference Address physical virtual Pointer Text Character String null-terminated Composite Algebraic data type generalized Array Associative array Class Dependent Equality Inductive Intersection List Object metaobject Option type Product Record or Struct Refinement Set Union tagged Other Any type Boolean Bottom type Collection Enumerated type Exception Function type Opaque data type Recursive data type Semaphore Stream Strongly typed identifier Type class Empty type Unit type Void Related topics Value Abstract data type Boxing Data structure Generic Kind metaclass Parametric polymorphism Primitive data type Interface Subtyping Type constructor Type conversion Type system Type theory Variable

---
Adapted from the Wikipedia article [Byte](https://en.wikipedia.org/wiki/Byte) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Byte?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.