Unique binary prefixes

Early suggestions

While aboriginal computer scientists about acclimated k to beggarly 1000, some accustomed the accessibility that would aftereffect from alive with multiples of 1024 and the abashing that resulted from application the aforementioned prefixes for two altered meanings.

Several proposals for different bifold prefixesdefn. 2 were fabricated in 1968. Donald Morrison proposed to use the Greek letter kappa (κ) to denote 1024, κ2 to denote 1024×1024, and so on.51 (At the time, anamnesis admeasurement was small, and alone K was in boundless use.) Wallace Givens responded with a angle to use bK as an abridgement for 1024 and bK2 or bK2 for 1024×1024, admitting he acclaimed that neither the Greek letter nor lowercase letter b would be simple to carbon on computer printers of the day.52 Bruce A. Martin added proposed that the prefixes be alone altogether, and the letter B be acclimated as a bifold exponent, agnate to E notation, to actualize shorthands like 3B20 for 3×22053

None of these acquired abundant acceptance, and assets of the letter K became the de facto accustomed for advertence a agency of 1024 instead of 1000, although this could not be connected to college powers.

As the alterity amid the two systems added in the college adjustment powers, added proposals for different prefixes were made. In 1996, Markus Kuhn proposed a arrangement with di prefixes, like the "dikilobyte" (K₂B or K2B).54

editIEC prefixes

The set of bifold prefixes that were eventually adopted, now referred to as the "IEC prefixes",defn. 5 were aboriginal proposed by the All-embracing Union of Pure and Applied Chemistry's (IUPAC) Interdivisional Committee on Nomenclature and Symbols (IDCNS) in 1995. At that time, it was proposed that the agreement kilobyte and megabyte be acclimated alone for 103 bytes and 106 bytes, respectively. The new prefixes kibi (kilobinary), mebi (megabinary) and gibi (gigabinary) were aswell proposed at the time, and the proposed symbols for the prefixes were kb, Mb and Gb respectively, rather than Ki, Mi and Gi.55 The angle was not accustomed at the time.

The Institute of Electrical and Electronic Engineers (IEEE) began to coact with the All-embracing Alignment for Acclimation (ISO) and All-embracing Electrotechnical Commission (IEC) to acquisition adequate names for bifold prefixes. The IEC proposed kibi, mebi, gibi and tebi, with the symbols Ki, Mi, Gi and Ti respectively, in 1996.56

The names for the new prefixes are acquired from the aboriginal SI prefixes accumulated with the appellation binary, but contracted, by demography the aboriginal two belletrist of the SI prefix and "bi" from binary. The aboriginal letter of anniversary such prefix is accordingly identical to the agnate SI prefixes, except for "K", which is acclimated interchangeably with "k", admitting in SI, alone the lower-case k represents 1000.

The IEEE absitively that their standards would use the prefixes kilo, etc. with their metric definitions, but accustomed the bifold definitions to be acclimated in an acting aeon as connected as such acceptance was absolutely acicular out on a case-by-case basis.57

editAdoption by IEC and NIST

In January 1999, the IEC appear the aboriginal all-embracing accustomed (IEC 60027-2 Amendment 2) with the new prefixes, connected up to pebi (Pi) and exbi (Ei).5859

The IEC 60027-2 Amendment 2 aswell states that the IEC position is the aforementioned as that of BIPM (the physique that regulates the SI system); the SI prefixes absorb their definitions in admiral of 1000 and are never acclimated to beggarly a ability of 1024.citation needed

In usage, articles and concepts about declared application admiral of 1024 would abide to be, but with the new IEC prefixes. For example, a anamnesis bore of 536870912 bytes (512×1048576) would be referred to as 512 MiB or 512 mebibytes instead of 512 MB or 512 megabytes. Conversely, back harder drives accept historically been marketed application the SI assemblage that "giga" agency 1000000000, a "500 GB" harder drive would still be labeled as such. According to these recommendations, operating systems and added software would aswell use bifold and SI prefixes in the aforementioned way, so the client of a "500 GB" harder drive would acquisition the operating arrangement advertisement either "500 GB" or "466 GiB", while 536870912 bytes of RAM would be displayed as "512 MiB".

The additional copy of the standard, appear in 2000,60 authentic them alone up to exbi,61 but in 2005, the third copy added prefixes zebi and yobi, appropriately analogous all SI prefixes with bifold counterparts.62

The harmonized ISO/IEC IEC 80000-13:2008 accustomed cancels and replaces subclauses 3.8 and 3.9 of IEC 60027-2:2005 (those defining prefixes for bifold multiples). The alone cogent change is the accession of absolute definitions for some quantities.63

editSpecific units of IEC 60027-2 A.2 and ISO/IEC 80000

IEC prefix Representations Customary prefix

Name Symbol Base 2 Base 1024 Value Base 10 Name Symbol

kibi Ki 210 10241 1024 ≈1.02×103 kilo k, K

mebi Mi 220 10242 1048576 ≈1.05×106 mega M

gibi Gi 230 10243 1073741824 ≈1.07×109 giga G

tebi Ti 240 10244 1099511627776 ≈1.10×1012 tera T

pebi Pi 250 10245 1125899906842624 ≈1.13×1015 peta P

exbi Ei 260 10246 1152921504606846976 ≈1.15×1018 exa E

zebi Zi 270 10247 1180591620717411303424 ≈1.18×1021 zetta Z

yobi Yi 280 10248 1208925819614629174706176 ≈1.21×1024 yotta Y

editOther standards bodies and organizations

The IEC-proposed bifold prefixes are now accurate by added acclimation bodies and abstruse organizations.

The United States National Institute of Standards and Technology (NIST) supports the ISO/IEC standards for "Prefixes for bifold multiples" and has a web website documenting them, anecdotic and answer their use. NIST suggests that in English, the aboriginal affricate of the name of the binary-multiple prefix should be arresting in the aforementioned way as the aboriginal affricate of the name of the agnate SI prefix, and that the additional affricate should be arresting as bee.1 NIST has declared the SI prefixes "refer carefully to admiral of 10" and that the bifold definitions "should not be used" for them.64

In December 2002, JEDEC, a arch standards alignment in the chip industry, mentioned the IEC prefixes in their Terms, Definitions, and Letter Symbols for Microcomputers, Microprocessors, and Anamnesis Integrated Circuits document. This certificate defines "kilo", "mega", and "giga" with bifold multipliers. A "Note" to this analogue again states that that analogue is alone presented "to reflect accepted usage", and quotes the IEC in anecdotic the bifold prefixes as "an another system".65 However, consecutive anamnesis standards appear by JEDEC still ascertain and use the prefixes kilo, mega, and giga as bifold multipliers.6667686970

On 19 March 2005, the IEEE accustomed IEEE 1541-2002 ("Prefixes for Bifold Multiples") was animated to a full-use accustomed by the IEEE Standards Association afterwards a two-year balloon period.7172 However, as of April 2008, the IEEE Publications analysis does not crave the use of IEC prefixes in its above magazines such as Spectrum73 or Computer.74

The All-embracing Bureau of Weights and Measures (BIPM), which maintains the All-embracing Arrangement of Units (SI), especially prohibits the use of SI prefixes to denote bifold multiples, and recommends the use of the IEC prefixes as an another back units of advice are not included in SI.7576

The Society of Automotive Engineers (SAE) prohibits the use of SI prefixes with annihilation but a power-of-1000 meaning, but does not acclaim or contrarily adduce the IEC bifold prefixes.77

The European Committee for Electrotechnical Acclimation (CENELEC) adopted the IEC-recommended bifold prefixes via the harmonization certificate HD 60027-2:2003-03.78 The European Union (EU) has appropriate the use of the IEC bifold prefixes back 2007.79

editDissent

Even a part of proponents of different prefixes for bifold multiples, proposals for another sets of prefixes accept connected afterward the addition of Ki, Mi, etc., by the IEC. For example, Donald Knuth, who uses decimal characters like 1 MB = 1000 kB,80 bidding "astonishment" that the IEC angle was adopted, calling them "funny-sounding" and opining that proponents were bold "that standards are automatically adopted just because they are there." Knuth proposed that the admiral of 1024 be appointed as "large kilobytes" and "large megabytes" (abbreviated KKB and MMB, as "doubling the letter connotes both binary-ness and large-ness").81 Double prefixes were already abolished from SI, however, accepting a multiplicative acceptation ("MMB" would be agnate to "TB"), and this proposed acceptance never acquired any traction.