Binary prefix

In computing, a bifold prefix is a specifier or catchword that is prepended to the units of agenda information, the bit and the byte, to announce multiplication by a ability of 2. In convenance the admiral acclimated are multiples of 10, so the prefixes denote admiral of 1024 = 210.

The computer industry uses agreement such as kilobyte, megabyte, and gigabyte, and agnate symbols KB, MB, and GB, in two altered ways. For example, in citations of capital anamnesis or RAM capacity, gigabyte commonly agency 1073741824 bytes. This is a ability of 2, accurately 230, accordingly this acceptance is referred to as a bifold assemblage or bifold prefix.

In a lot of added contexts, the industry uses kilo, mega, giga, etc., in a address constant with their acceptation in the International System of Units (SI): as admiral of 1000. For example, a 500 gigabyte harder drive holds 500000000000 bytes, and a 100 megabit per additional Ethernet affiliation transfers abstracts at 100000000 bit/s.

Starting in about 1998, a amount of standards and barter organizations accustomed standards and recommendations for a new set of bifold prefixes, proposed beforehand by the International Electrotechnical Commission (IEC), that would accredit actually to admiral of 1024. According to these, the SI prefixes would alone be acclimated in the decimal sense, even if apropos to abstracts accumulator capacities: kilobyte and megabyte would denote one thousand bytes and one actor bytes appropriately (consistent with SI), while new agreement such as kibibyte, mebibyte and gibibyte, abbreviated KiB, MiB, and GiB, would denote 1024 bytes, 1048576 bytes, and 1073741824 bytes respectively.1 However, as of 2011 acceptance of the new agreement has been apathetic and acceptance has been bound in the exchange and in the press,citation needed with notable exceptions such as Linux operating systems, several textbooks2 and accurate analysis papers

History

Main memory

Early computers acclimated one of two acclamation methods to admission the arrangement memory; bifold (base-2) or decimal (base-10).4 For example, the IBM 701 (1952) acclimated bifold and could abode 2048 36-bit words, while the IBM 702 (1953) acclimated decimal and could abode 10000 7-bit words.

By the mid 1960s, bifold acclamation had become the accepted architectonics in a lot of computer designs, and capital anamnesis sizes were a lot of frequently admiral of two. This is the a lot of accustomed agreement for memory, as all combinations of their abode curve map to a accurate address, acceptance simple accession into a beyond block of anamnesis with abutting addresses.

Early computer arrangement affidavit would specify the anamnesis admeasurement with an exact amount such as 4096, 8192, or 16384 words of storage. These are all admiral of 2, and along are baby multiples of 210, or 1024. As accumulator capacities increased, several altered methods were developed to abridge these quantities.

The adjustment a lot of frequently acclimated today uses prefixes such as kilo, mega, giga, and agnate symbols K, M, and G, which the computer industry originally adopted from the metric system. The prefixes kilo- and mega-, acceptation 1000 and 1000000 respectively, were frequently acclimated in the electronics industry afore World War II.5 Along with giga- or G-, acceptation 1000000000, they are now accepted as SI prefixesdefn. 1 afterwards the International Arrangement of Units (SI), alien in 1960 to ascertain aspects of the metric system, although K is the SI assemblage for temperature (kelvin) and should not be alloyed up with k, the SI prefix for kilo.

The International Arrangement of Units does not ascertain units for agenda advice but addendum that the SI prefixes may be activated alfresco the contexts area abject units or acquired units would be used. But as computer capital anamnesis in a binary-addressed arrangement is bogus in sizes that were calmly bidding as multiples of 1024, kilobyte, if activated to computer memory, came to be acclimated to beggarly 1024 bytes instead of 1000. (SI absolutely prohibits this usage, advertence that the prefixes alone accept the 1000-based meaning, and cannot be acclimated as placeholders for added numbers, like 1024.)6

The use of K in the bifold faculty as in a "32K core" acceptation 32×1024, or 32768, can be begin as aboriginal as 1959.78 Gene Amdahl's seminal 1964 commodity on IBM System/360 acclimated 1K to beggarly 1024.9 This appearance was acclimated by added computer vendors, the CDC 7600 Arrangement Description (1968) fabricated all-encompassing use of K as 1024.10 Thus the aboriginal bifold prefix was born.defn. 2

Another appearance was to abbreviate the endure 3 digits and adjoin K, about application K as a decimal prefixdefn. 3 agnate to SI, but consistently truncating to the next lower accomplished amount instead of rounding to the nearest. The exact ethics 32768, 65536 and 131072 would again be declared as 32K, 65K and 131K.11 (If these ethics had been angled they would accept become 33K, 66K, and 131K, respectively.) This appearance was acclimated from about 1965 to 1975.

These two styles (K = 1024 and truncation) were acclimated about about the aforementioned time, sometimes by the aforementioned company. In discussions of binary-addressed memories, the exact admeasurement was axiomatic from context. (For anamnesis sizes of 32K and below, there is no aberration amid the two styles.) The HP 21MX real-time computer (1974) denoted 196608 (which is 192×1024) as 196K and 1048576 as 1M,12 while the HP 3000 business computer (1973) could accept 64K, 96K, or 128K bytes of memory.13

The "truncation" adjustment gradually waned. Capitalization of the letter K became the de facto accepted for bifold notation, although this could not be continued to college powers. Nevertheless, the convenance of application the SI-inspired "kilo" to announce 1024 was after continued to "megabyte" acceptation 10242 (1048576) bytes, and after "gigabyte" for 10243 (1073741824) bytes. For example, a "512 megabyte" RAM bore is 512×10242 bytes (512×1048576, or 536870912), rather than 512000000.

The symbols Kbit, Kbyte, Mbit and Mbyte started to be acclimated as "binary units"—"bit" or "byte" with a multiplier that is a ability of 1024—in the aboriginal 1970s.14 For a time, anamnesis capacities were generally bidding in K, even if M could accept been used: The IBM System/370 Model 158 advertisement (1972) had the following: "Real accumulator accommodation is accessible in 512K increments alignment from 512K to 2,048K bytes."15

Megabyte was acclimated to call the 22-bit acclamation of DEC PDP-11/70 (1975)16 and gigabyte the 30-bit acclamation DEC VAX-11/780 (1977).

editDisk drives

The deejay drive industry followed a altered pattern. Industry practice, added thoroughly accurate at Timeline of bifold prefixes and continuing today, is to specify harder drives application SI prefixes and symbols in their SI or "decimal" interpretation. Unlike binary-addressed computer capital memory, there is annihilation in a deejay drive that influences it to accept a absolute accommodation calmly bidding application a ability of 1024. The aboriginal commercially awash deejay drive, the IBM 350, had 50 (not 32 or 64) concrete deejay "platters" absolute a absolute of 50,000 sectors of 100 characters each, for a absolute quoted accommodation of "5 actor characters."17 It was alien in September 1956.

In the 1960s a lot of deejay drives acclimated IBM's capricious block breadth architecture (called Count Key Abstracts or "CKD").18 Any block admeasurement could be authentic up to the best clue length. Since the block headers alive space, the accessible accommodation of the drive was abased on the block size. Blocks ("records" in IBM's terminology) of 88, 96, 880 and 960 were generally acclimated because they accompanying to the anchored block admeasurement of bite cards. The drive accommodation was usually declared beneath altitude of abounding clue almanac blocking. For example, the 100 megabyte 3336 deejay backpack alone accomplished that accommodation with a abounding clue block admeasurement of 13,030 bytes.

Hard deejay drive manufacturers acclimated "megabytes" or "MB", acceptation 106 bytes, to characterize their articles as aboriginal as 1974.19 By 1977, in its aboriginal edition, Disk/Trend, a arch harder deejay drive industry business consultancy anecdotal the industry according to MBs (decimal sense) of capacity.20

One of the ancient harder deejay drives in claimed accretion history, the Seagate ST-412, was authentic as "Formatted: 10.0 Megabytes".21 The blueprint of 4 alive or alive surfaces (tracks per cylinder), 306 cylinders and if formatted with a area admeasurement of 256 bytes and 32 sectors/track after-effects in a accommodation of 10027008 bytes. This drive was one of several types installed into the IBM PC/XT 22 and abundantly advertised and appear as a "10 MB" (formatted) harder deejay drive.23 Operating systems and programs application the accepted bifold prefixesdefn. 4 appearance this as 9.5625 MB.

The harder drive industry continues to use decimal prefixes for drive capacity. Today, for example, a "300 GB" harder drive offers hardly added than 300×109, or 300000000000, bytes, not 300×230 (which would be about 322×109). Operating systems such as Microsoft Windows that affectation harder drive sizes application the accepted bifold prefix "GB" (as it is acclimated for RAM) would affectation this as 279.4 GB (meaning 279.4×10243, or 279.4×1073741824).

However, added usages still occur. For example, in one document, Seagate specifies abstracts alteration ante of some of its harder drives in both IEC and decimal units.24 "Advanced Format" drives application 4096-byte sectors are declared as accepting "4K sectors."25

editInformation alteration and alarm rates

Like the harder drive, there is annihilation in a computer alarm ambit or abstracts alteration aisle that demands or even encourages that things appear at ante calmly bidding application admiral of 1024, or even application admiral of 2.

Computer alarm frequencies are consistently quoted application SI prefixes in their decimal sense. For example, the centralized alarm abundance of the aboriginal IBM PC was 4.77 MHz, that is, 4770000 Hz.

Similarly, agenda advice alteration ante are mostly quoted application decimal prefixes:

The ATA-100 deejay interface refers to 100000000bytes/s

1x CD-ROM CD-ROM acceleration is 150K or 150000bytes/s

A "56K" modem refers to 56000bits/s

SATA-2 has a raw bit amount of 3 Gbit/s = 3000000000bits/s

PC2-6400 ram transfers 6400000000bytes/s

Firewire 800 has a raw amount of 800000000bits/s

As of 2011, Seagate specifies the alteration acceleration of some harder deejay drives with IEC bifold prefixes as able-bodied as decimal.24

editStandardization of bifold definitions

By the mid 1970s it was accepted to see K acceptation 1024 and the casual M acceptation 1048576 for words or bytes of capital anamnesis (RAM) while K and M were frequently acclimated with their decimal acceptation for deejay storage. In the 1980s, as capacities of both types of accessories increased, the SI prefix G, with SI meaning, was frequently activated to deejay storage, while M in its bifold meaning, became accepted for computer memory. In the 1990s, the prefix G, in its bifold meaning, became frequently acclimated for computer anamnesis capacity. The aboriginal terabyte (SI prefix, 1000000000000 bytes) harder deejay drive was alien in 2007.26

The bifold acceptance of the kilo, mega, and giga prefixes and their agnate symbols K, M, and G as both admiral of 1000 and admiral of 1024 was recorded in standards and dictionaries. For example, the 1986 ANSI/IEEE Std 1084-198627 authentic bifold uses for kilo and mega.

kilo (K). (1) A prefix advertence 1000. (2) In statements involving admeasurement of computer storage, a prefix advertence 210, or 1024.

mega (M). (1) A prefix advertence one million. (2) In statements involving admeasurement of computer storage, a prefix advertence 220, or 1048576.

The bifold units Kbyte and Mbyte were formally authentic in ANSI/IEEE Std 1212-1991.28

Many dictionaries accept acclaimed the convenance of application acceptable prefixes to announce bifold multiples.2930 Oxford online concordance defines, for example, megabyte as: "Computing: a assemblage of advice according to one actor or (strictly) 1048576bytes."31

The units Kbyte, Mbyte, and Gbyte are begin in the barter columnist and in IEEE journals. Gigabyte was formally authentic in IEEE Std 610.10-1994 as either 1000000000 or 230 bytes.32 Kilobyte, Kbyte, and KB are agnate units and all are authentic in the accepted standard, IEEE 100-2000.33 Byte multiples application admiral of 1024 up to yottabyte are accustomed by the on-line accretion concordance FOLDOC (Free On-Line Concordance of Computing).34

The accouterments industry has coped with the bifold definitions because of about consistency: arrangement anamnesis (RAM) about uses the bifold acceptation while alluring deejay accumulator uses the SI meaning. There are, however, exceptions and appropriate cases. Diskettes use yet addition "megabyte" according to 1024×1000 bytes.35 In optical disks, Compact Disks use MB to beggarly 10242 bytes while DVDs use GB to beggarly 10003 bytes

Inconsistent use of units

Deviation amid admiral of 1024 and admiral of 1000

Computer accumulator has become cheaper per assemblage and thereby larger, by abounding orders of consequence back "K" was aboriginal acclimated to beggarly 1024. Because both the SI and "binary" meanings of kilo, mega, etc., are based on admiral of 1000 or 1024 rather than simple multiples, the aberration amid 1M "binary" and 1M "decimal" is proportionally beyond than that amid 1K "binary" and 1k "decimal," and so on up the scale. The about aberration amid the ethics in the bifold and decimal interpretations increases, if appliance the SI prefixes as the base, from 2.4% for kilo to over 20% for the yotta prefix.

Linear-log blueprint of allotment of the aberration amid decimal and bifold interpretations of the assemblage prefixes adjoin the accumulator size.

Prefix Bin ÷ Dec Dec ÷ Bin Percentage difference

kilo 1.024 0.9766 +2.4% or −2.3%

mega 1.049 0.9537 +4.9% or −4.6%

giga 1.074 0.9313 +7.4% or −6.9%

tera 1.100 0.9095 +10.0% or −9.1%

peta 1.126 0.8882 +12.6% or −11.2%

exa 1.153 0.8674 +15.3% or −13.3%

zetta 1.181 0.8470 +18.1% or −15.3%

yotta 1.209 0.8272 +20.9% or −17.3%

editConsumer confusion

In the aboriginal canicule of computers there was little or no customer abashing because of the adult attributes of the consumers and the convenance of computer manufacturers to specify their articles with capacities in abounding precision. For example, in 1965 IBM declared about the System/360 Model 75 that "Its capital anamnesis operated at 750 nanoseconds and was attainable in three sizes up to 1,048,576 characters of information."38

One antecedent of customer abashing is the aberration in the way abounding operating systems affectation harder drive sizes, compared to the way harder drive manufacturers call them. As acclaimed previously, harder drives are declared and awash appliance "GB" or "TB" in their SI meaning: one billion and one abundance bytes. Abounding operating systems and added software about affectation harder drive and book sizes appliance "MB", "GB" or added SI-looking prefixes in their "binary" meaning, just as they do for displays of RAM capacity. (The ancient accepted presentation of harder deejay drive accommodation by an operating arrangement appliance "KB" or "MB" in a bifold faculty is 1984;39 beforehand operating systems about presented harder deejay drive accommodation in decimal digits with no prefix of any sort, for example, in the achievement of the MS-DOS or PC-DOS CHKDSK command.)

The afterward three images appearance the alterity of advertisement the identical deejay accommodation on the manufacturer's packaging (160 GB = 160×10003), the Windows XP deejay administrator (149.05 GB = 149.05×10243), and the drive backdrop affectation (152625MB = 152625×10242).

Disk drive packaging specifies a deejay accommodation of 160×109 bytes appliance accepted SI prefixes.

Windows XP deejay administration appliance lists the accommodation of a 160×109 byte deejay drive as 149.05 GB

Windows XP drive backdrop affectation lists the accommodation of a 160×109 byte deejay drive as 152625 MB.

editLegal disputes

The altered interpretations of deejay admeasurement prefixes has led to three cogent chic activity lawsuits adjoin agenda accumulator manufacturers. One case complex beam anamnesis and the added two complex harder deejay drives. Both were acclimatized with the manufacturers acceptance no atrocity but accordant to analyze the accumulator accommodation of their articles on the customer packaging. Beam anamnesis and harder deejay manufacturers now accept disclaimers on their packaging and web sites allegorical the formatted accommodation of the devices40 or defining MB as 1 actor bytes and 1 GB as 1 billion bytes.41

editWillem Vroegh v. Eastman Kodak Company

On 20 February 2004, Willem Vroegh filed a accusation adjoin Lexar Media, Dane–Elec Memory, Fuji Photo Film USA, Eastman Kodak Company, Kingston Technology Company, Inc., Memorex Products, Inc.; PNY Technologies Inc., SanDisk Corporation, Verbatim Corporation, and Viking Interworks alleging that their descriptions of the accommodation of their beam anamnesis cards were apocryphal and misleading.

Vroegh claimed that a 256 MB Beam Anamnesis Device had alone 244 MB of attainable memory. "Plaintiffs adduce that Defendants marketed the anamnesis accommodation of their articles by bold that one megabyte equals one actor bytes and one gigabyte equals one billion bytes." The plaintiffs capital the defendants to use the acceptable ethics of 10242 for megabyte and 10243 for gigabyte. The plaintiffs accustomed that the IEC and IEEE standards ascertain a MB as one actor bytes but declared that the industry has abundantly abandoned the IEC standards.42

The manufacturers agreed to analyze the beam anamnesis agenda accommodation on the packaging and web sites.43 The consumers could administer for "a abatement of ten percent off a approaching online acquirement from Defendants' Online Stores Beam Anamnesis Device".44

editOrin Safier v. Western Agenda Corporation

On 7 July 2005, an activity advantaged Orin Safier v. Western Agenda Corporation, et al. was filed in the Superior Court for the City and County of San Francisco, Case No. CGC-05-442812. The case was after confused to the Northern District of California, Case No. 05-03353 BZ.45

Although Western Agenda maintained that their acceptance of units is constant with "the absolutely actual industry accepted for barometer and anecdotic accumulator capacity", and that they "cannot be accepted to ameliorate the software industry", they agreed to achieve in March 2006 with 14 June 2006 as the Final Approval audition date.46

Western Agenda offered to atone barter with a chargeless download of advancement and accretion software admired at US$30. They aswell paid $500,000 in fees and costs to San Francisco attorneys Adam Gutride and Seth Safier, who filed the suit. The adjustment alleged for Western Agenda to add a abnegation to their after packaging and advertising.474849

editCho v. Seagate Technology (US) Holdings, Inc.

A accusation (Cho v. Seagate Technology (US) Holdings, Inc., San Francisco Superior Court, Case No. CGC-06-453195) was filed adjoin Seagate Technology, alleging that Seagate overrepresented the bulk of accessible accumulator by 7% on harder drives awash amid March 22, 2001 and September 26, 2007. The case was acclimatized after Seagate acceptance wrongdoing, but accordant to accumulation those purchasers with chargeless advancement software or a 5% acquittance on the amount of the drives

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.

Current practice

Most computer accouterments uses SI prefixesdefn. 1 to accompaniment accommodation and ascertain added achievement ambit such as abstracts rate. Main and accumulation memories are notable exceptions.

Main anamnesis and accumulation anamnesis universally use accepted bifold prefixesdefn. 4 to accompaniment capacity.8283848586 On the added hand, beam memory, like that begin in solid accompaniment drives, uses SI prefixesdefn. 1 to accompaniment capacity.citation needed

With a few exceptions, a lot of operating systems and added software abide to use the accepted bifold prefixes in displays of memory, deejay accumulator capacity, and book size, but SI prefixesdefn. 1 in added areas such as arrangement advice speeds and processor speeds.

In the afterward subsections, unless contrarily noted, examples are aboriginal accustomed application the accepted prefixes acclimated in anniversary case, and again followed by estimation application added characters area appropriate.

editOperating systems

Prior to the absolution of Macintosh Arrangement Software (1984), book sizes were about appear by the operating arrangement after any prefixes.citation needed Today, a lot of operating systems address book sizes with prefixes.

The Linux atom uses bifold prefixes if booting up.8788 However, abounding Unix-like arrangement utilities like the ls command, use admiral of 1024 adumbrated as KB/MB (customary bifold prefixes).

The Ubuntu GNU/Linux administration uses the IEC prefixes for base-2 numbers as of the 10.10 release.8990

Microsoft Windows letters book sizes and deejay accessory capacities application the accepted bifold prefixes or, in a "Properties" dialog, application the exact amount in bytes.

Since Mac OS X Snow Leopard, Apple's Mac OS X letters sizes application SI decimal prefixes (1 MB = 1,000,000 bytes).9192

editSoftware

As of February 2010, a lot of software does not analyze symbols for bifold and decimal prefixes.defn. 3 The IEC bifold allotment assemblage has been adopted by a few, but this is not acclimated universally.

One of the declared goals of the addition of the IEC prefixes was "to bottle the SI prefixes as actual decimal multipliers."71 Programs such as fdisk/cfdisk, parted, and apt-get use SI prefixes with their decimal meaning.

GNOME's allotment editor uses IEC prefixes to affectation allotment sizes. The absolute accommodation of the 120×109 byte deejay is displayed as "111.79 GiB"

GNOME's arrangement adviser uses IEC prefixes to appearance anamnesis admeasurement and networking abstracts rate.

BitTornado uses accepted SI prefixes for abstracts ante and IEC prefixes for book sizes

Deluge (BitTorrent client) uses IEC prefixes for abstracts ante as able-bodied as book sizes

Linux's fdisk uses accepted SI prefixes to affectation a 160×109 byte deejay as "160.0 GB"

Example of the use of IEC bifold prefixes in the Linux operating arrangement announcement cartage aggregate on a arrangement interface in kibibytes (KiB) and mebibytes (MiB), as acquired with the ifconfig utility:

eth0 Link encap:Ethernet HWaddr 00:14:A0:B0:7A:42

inet6 addr: 2001:491:890a:1:214:a5ff:febe:7a42/64 Scope:Global

inet6 addr: fe80::214:a5ff:febe:7a42/64 Scope:Link

UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

RX packets:254804 errors:0 dropped:0 overruns:0 frame:0

TX packets:756 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:18613795 (17.7 MiB) TX bytes:45708 (44.6 KiB)

Software that uses accepted SI prefixes for admiral of 1000, but not IEC bifold prefixes for admiral of 1024, includes:

Mac OS X v10.6 and after for harder drive and book sizes9394

Software that uses IEC bifold prefixes for admiral of 1024 and uses accepted SI prefixes for admiral of 1000 includes:

GNU Core Utilities95

Flyspray96

bugs.mysql.com97

GParted98

DFSee99

disktype100

raidutil101

FreeDOS-32102

ifconfig103

GNOME Network104

SLIB105

Cygwin/X106

HTTrack107

Pidgin (IM client)108

Deluge109

zFTPServer110

yafc111

tnftp112

WinSCP113

MediaInfo114

editComputer hardware

As of February 2010, no examples of accouterments marketed application IEC bifold prefixes accept been found. Even accouterments types that use powers-of-1024 multipliers, such as memory, abide to be marketed with accepted bifold prefixes.

editComputer memory

The 536,870,912 byte (512×220) accommodation of these RAM modules is declared as "512 MB" on the label.

Measurements of a lot of types of cyberbanking anamnesis such as RAM, ROM are accustomed application accepted bifold prefixes (kilo, mega, and giga). This includes some beam memory, like EEPROMs. For example, a "512 megabyte" anamnesis bore is 512×220 bytes (512×1048576, or 536870912).

JEDEC Solid Accompaniment Technology Association, the semiconductor engineering acclimation physique of the Cyberbanking Industries Alliance (EIA), continues to cover the accepted bifold definitions of kilo, mega and giga in their Terms, Definitions, and Letter Symbols document,65 and uses those definitions in after anamnesis standards6667686970 (See aswell JEDEC anamnesis standards.)

Many computer programming tasks advertence anamnesis in agreement of admiral of two because of the inherent bifold architecture of accepted accouterments acclamation systems. For example, a 16-bit processor annals can advertence at a lot of 65,536 items (bytes, words, or added objects); this is calmly bidding as "64K" items. An operating arrangement ability map anamnesis as 4096-byte pages, in which case absolutely 8192 pages could be allocated aural 33554432bytes of memory: 8K (8192) pages of 4 kilobytes (4096) anniversary aural 32 megabytes (32 MiB) of memory.

editHard deejay drives

All harder deejay drive manufacturers accompaniment accommodation application SI prefixes.defn. 1115

editFlash drives

USB beam drives, flash-based anamnesis cards like CompactFlash or Secure Digital, and flash-based SSDs use SI prefixes;defn. 1 for example, a "256 MB" beam agenda provides at atomic 256 actor bytes (256000000), not 256×1024×1024 (268435456).40 These accessories usually physically accommodate the bifold capacities, but some amplitude is aloof for centralized functions of the beam drive. In added words, there are physically 256×1024×1024 bytes of accumulator on a archetypal "256 MB" beam drive, but some amplitude is bare for functions like abrasion leveling. In the case of a "256 MB" beam drive, the architect can admeasure about 12 MB to centralized functions, and still accommodate 256 actor accessible bytes.

editFloppy drives

Floppy disks accept existed in abundant concrete and analytic formats, and accept been sized inconsistently. In part, this is because the end user accommodation of a authentic deejay is a action of the ambassador hardware, so that the aforementioned deejay could be formatted to a array of capacities. In abounding cases, the media are marketed after any adumbration of the end user capacity, as for example, DSDD, acceptation double-sided double-density.

The endure broadly adopted diskette was the 3½ inch top density. This has a formatted accommodation of 1474560 bytes or 1440 KB (1440×1024, application "KB" in the accepted bifold sense). These are marketed as "HD", or "1.44 MB" or both. This case defines a "third megabyte" of 1000×1024.

Most operating systems affectation the accommodation application "MB" in the accepted bifold sense, consistent in a affectation of "1.4 MB" (1.40625 MB). Some users accept noticed the missing 0.04 MB and both Apple and Microsoft accept abutment bulletins apropos to them as 1.4 MB.35

The beforehand 1200 KB (1200×1024) 5¼ inch diskette awash with the IBM PC AT was marketed as 1.2 MB (1.171875 MiB). The better 8 inch diskette formats could accommodate added than a megabyte, and the capacities of those accessories were generally anyhow defined in megabytes, aswell after controversy.

Older and abate diskette formats were usually articular as an authentic amount of (binary) KB, for archetype the Apple Deejay II declared as 140KB had a 140×1024 byte capacity, and the aboriginal "360KB" bifold sided, bifold body deejay drive acclimated on the IBM PC had a 360×1024 byte capacity.

In abounding cases diskette accouterments was marketed based on unformatted capacity, and the aerial appropriate to architecture sectors on the media would abate the nominal accommodation as able-bodied (and this aerial about assorted based on the admeasurement of the formatted sectors), arch to added irregularities.

editOptical discs

The capacities of a lot of optical disc accumulator media like DVD, Blu-ray Disc, HD DVD and magneto-optical (MO) are accustomed application SI decimal prefixes. A "4.7 GB" DVD has a nominal accommodation of about 4.38 GiB.37 However, CD capacities are consistently accustomed application accepted bifold prefixes. Thus a "700 MB" (or "80 minute") CD has a nominal accommodation of about 700 MiB (approx 730 MB).36

editTape drives and media

Tape drive and media manufacturers use SI decimal prefixes to analyze capacity.116

editData manual and alarm rates

Certain units are consistently acclimated with SI decimal prefixes even in accretion contexts. Two examples are hertz (Hz), which is acclimated to admeasurement the alarm ante of cyberbanking components, and bit/s, acclimated to admeasurement abstracts manual speed.

A 1 GHz processor receives 1000000000 alarm ticks per second

A complete book sampled at 44.1 kHz has 44100 samples per second

A 128 kbit/s MP3 beck consumes 128000bits (16 kilobytes, 15.6 KiB) per second

A 1 Mbit/s Internet affiliation can alteration 1000000bits per additional (125000 bytes per additional ≈ 122 KiB/s, bold an 8-bit byte and no overhead)

A 1 Gbit/s Ethernet affiliation can alteration 1000000000bits per additional (125000000 bytes per additional ≈ 119 MiB/s, bold an 8-bit byte and no overhead)

A 56k modem transfers 56000 $.25 per additional ≈ 6.8 KiB/s.

Bus alarm speeds and accordingly bandwidths are both quoted application SI decimal prefixes.

PC3200 anamnesis on a bifold abstracts amount bus, appointment 8 bytes per aeon with a alarm acceleration of 200 MHz (200000000cycles per second) has a bandwidth of 200000000×8×2 = 3200000000bytes/second = 3.2 GB/s (about 3.0 GiB/s).

A PCI-X bus at 66 MHz (66000000cycles per second), 64 $.25 per transfer, has a bandwidth of 66000000transfers/second×64bits/transfer = 4224000000bits/second, or 528000000bytes/second, usually quoted as 528 MB/s (about 503 MiB/s).

editWebsites and government agencies

The UK government117

The Pirate Bay118

Ars Technica119

Anandtech120