Editing Binary prefix (section)

== History ==
{{See also|Timeline of binary prefixes}}

=== Early prefixes ===
The original [[metric system]] adopted by France in 1795 included two binary prefixes named ''[[double (metric prefix)|double]]-'' (2×) and ''[[demi (metric prefix)|demi]]-'' ({{sfrac|1|2}}×).<ref name="frev1795" /> However, these were not retained when the [[SI prefix]]es were internationally adopted by the 11th [[Conférence générale des poids et mesures|CGPM conference]] in 1960.

=== Storage capacity ===
==== Main memory ====
Early computers used one of two addressing methods to access the system memory; binary (base 2) or decimal (base 10).<ref name="weik1961" /> For example, the [[IBM 701]] (1952) used a binary methods and could address 2048 [[Word (computer architecture)|word]]s of 36 [[bit]]s each, while the [[IBM 702]] (1953) used a decimal system, and could address ten thousand 7-bit words.

By the mid-1960s, binary addressing had become the standard architecture in most computer designs, and main memory sizes were most commonly powers of two. This is the most natural configuration for memory, as all combinations of states of their [[address line]]s map to a valid address, allowing easy aggregation into a larger block of memory with contiguous addresses.

While early documentation specified those memory sizes as exact numbers such as 4096, 8192, or {{val|16384}} units (usually [[word (computer architecture)|word]]s, bytes, or bits), computer professionals also started using the long-established metric system prefixes "kilo", "mega", "giga", etc., defined to be powers of 10,<ref name="BIPM8" /> to mean instead the nearest powers of two; namely, 2<sup>10</sup> = 1024, 2<sup>20</sup> = 1024<sup>2</sup>, 2<sup>30</sup> = 1024<sup>3</sup>, etc.<ref name="blais1930" /><ref name="liny1972" /> The corresponding metric prefix symbols ("k", "M", "G", etc.) were used with the same binary meanings.<ref name="real1959" /><ref name="gruen1960" /> The symbol for 2<sup>10</sup> = 1024 could be written either in lower case ("k")<ref name="horak2008" /><ref name="dodd1997" /><ref name="laver1989" /> or in uppercase ("K"). The latter was often used intentionally to indicate the binary rather than decimal meaning.<ref name="amda1964" /> This convention, which could not be extended to higher powers, was widely used in the documentation of the [[IBM&nbsp;360]] (1964)<ref name="amda1964" /> and of the [[IBM System/370]] (1972),<ref name="IBM1972" /> of the [[CDC&nbsp;7600]],<ref name="CDC7600" /> of the DEC [[PDP-11]]/70 (1975)<ref name="bell1975" /> and of the DEC [[VAX-11/780]] (1977).{{citation needed|date=August 2023}}

In other documents, however, the metric prefixes and their symbols were used to denote powers of 10, but usually with the understanding that the values given were approximate, often truncated down. Thus, for example, a 1967 document by [[Control Data Corporation]] (CDC) abbreviated "2<sup>16</sup> = {{nowrap|64 × 1024}} = {{val|65536}} words" as "65K words" (rather than "64K" or "66K"),<ref name="CDC1967" /> while the documentation of the [[HP 2100|HP 21MX]] real-time computer (1974) denoted {{nowrap|3 × 2<sup>16</sup>}} = {{nowrap|192 × 1024}} = {{val|196608}} as "196K" and 2<sup>20</sup> = {{val|1048576}} as "1M".<ref name="frank1974" />

These three possible meanings of "k" and "K" ("1024", "1000", or "approximately 1000") were used loosely around the same time, sometimes by the same company. The [[HP 3000]] business computer (1973) could have "64K", "96K", or "128K" bytes of memory.<ref name="HP1973" /> The use of SI prefixes, and the use of "K" instead of "k" remained popular in computer-related publications well into the 21st century, although the ambiguity persisted. The correct meaning was often clear from the context; for instance, in a binary-addressed computer, the true memory size had to be either a power of 2, or a small integer multiple thereof. Thus a "512 megabyte" RAM module was generally understood to have {{nowrap|512 × 1024<sup>2</sup>}} = {{val|536870912}} bytes, rather than {{val|512000000}}.

==== Hard disks ====
In specifying disk drive capacities, manufacturers have always used conventional decimal SI prefixes representing powers of 10. Storage in a rotating [[disk drive]] is organized in platters and tracks whose sizes and counts are determined by mechanical engineering constraints so that the capacity of a disk drive has hardly ever been a simple multiple of a power of 2. For example, the first commercially sold disk drive, the [[IBM 350]] (1956), had 50 physical disk platters containing a total of {{val|50000}} sectors of 100 characters each, for a total quoted capacity of 5 million characters.<ref name="IBM1956" />

Moreover, since the 1960s, many disk drives used IBM's [[Count Key Data|disk format]], where each track was divided into blocks of user-specified size; and the block sizes were recorded on the disk, subtracting from the usable capacity. For example, the IBM 3336 disk pack was quoted to have a 200-megabyte capacity, achieved only with a single {{val|13030}}-byte block in each of its 808 × 19 tracks.

Decimal megabytes were used for disk capacity by the CDC in 1974.<ref name="CDC1974" /> The Seagate [[ST-412]],<ref name="seag1982" /> one of several types installed in the [[IBM PC/XT]],<ref name="CSN1984" /> had a capacity of {{val|10027008|u=bytes}} when formatted as 306 × 4 tracks and 32 256-byte sectors per track, which was quoted as "10&nbsp;MB".<ref name="mall2011" /> Similarly, a "300&nbsp;GB" hard drive can be expected to offer only slightly more than {{val|300|e=9}} = {{val|300000000000}}, bytes, not {{nowrap|300 × 2<sup>30</sup>}} (which would be about {{val|322|e=9}} bytes or "322&nbsp;GB"). The first terabyte (SI prefix, {{val|1000000000000}} bytes) hard disk drive was introduced in 2007.<ref name="hita2007" /> Decimal prefixes were generally used by information processing publications when comparing hard disk capacities.<ref name="RDD1977" />

Some programs and operating systems, such as [[Microsoft Windows]], still use "MB" and "GB" to denote binary prefixes even when displaying disk drive capacities and file sizes, as did [[Classic Mac OS]]. Thus, for example, the capacity of a "10 MB" (decimal "M") disk drive could be reported as "{{nowrap|9.56 MB}}", and that of a "300&nbsp;GB" drive as "279.4&nbsp;GB". Some operating systems, such as [[Mac OS X]],<ref>{{cite web |title=How iOS and macOS report storage capacity |url=https://support.apple.com/en-us/HT201402 |website=Apple Support |access-date=9 January 2022 |language=en |date=27 February 2018 |archive-date=9 April 2020 |archive-url=https://web.archive.org/web/20200409170256/https://support.apple.com/en-us/HT201402 |url-status=live }}</ref> [[Ubuntu]],<ref>{{cite web |title=UnitsPolicy |url=https://wiki.ubuntu.com/UnitsPolicy |website=Ubuntu Wiki |publisher=Ubuntu |access-date=9 January 2022 |archive-date=18 November 2021 |archive-url=https://web.archive.org/web/20211118114902/https://wiki.ubuntu.com/UnitsPolicy |url-status=live }}</ref> and [[Debian]],<ref>{{cite web |title=ConsistentUnitPrefixes |url=https://wiki.debian.org/ConsistentUnitPrefixes |website=Debian Wiki |access-date=9 January 2022 |archive-date=3 December 2021 |archive-url=https://web.archive.org/web/20211203075715/https://wiki.debian.org/ConsistentUnitPrefixes |url-status=live }}</ref> have been updated to use "MB" and "GB" to denote decimal prefixes when displaying disk drive capacities and file sizes. Some manufacturers, such as [[Seagate Technology]], have released recommendations stating that properly-written software and documentation should specify clearly whether prefixes such as "K", "M", or "G" mean binary or decimal multipliers.<ref name="seaga2011" /><ref name="seag2010" />

==== Floppy disks ====
[[Floppy disks]] used [[List of floppy disk formats|a variety of formats]], and their capacities was usually specified with SI-like prefixes "K" and "M" with either decimal or binary meaning. The capacity of the disks was often specified without accounting for the internal [[disk formatting|formatting]] overhead, leading to more irregularities.

The early 8-inch diskette formats could contain less than a megabyte with the capacities of those devices specified in kilobytes, kilobits or megabits.<ref>{{Cite web |date=2012-03-07 |title=IBM100 – The Floppy Disk |url=http://www-03.ibm.com/ibm/history/ibm100/us/en/icons/floppy/breakthroughs/ |archive-url=https://web.archive.org/web/20120403025215/http://www-03.ibm.com/ibm/history/ibm100/us/en/icons/floppy/breakthroughs/ |url-status=dead |archive-date=3 April 2012 |access-date=2023-10-17 |website=www-03.ibm.com |language=en-US}}</ref><ref>{{cite magazine|magazine=Datamation |title=Disc Storage |date= May 1972 |pages=154, 162, 164 |quote= CDS 100 ... stores over 600 kilobits, Model 650 ... store 1.5 megabits ... }}</ref>

The 5.25-inch diskette sold with the [[PC AT|IBM PC AT]] could hold {{nowrap|1200 × 1024}} = {{val|1228800}} bytes, and thus was marketed as "1200&nbsp;KB" with the binary sense of "KB".<ref>{{Cite web |last=Brutman |first=Michael B. |date=July 8, 2001 |title=Working with Disks: An intro to floppy disks and floppy drives |url=http://brutmanlabs.org/Diskettes/Diskette_handling.html |website=Brutmanlabs |access-date=2024-02-19  |archive-date=2024-02-19  |archive-url=https://web.archive.org/web/20240219085221/http://brutmanlabs.org/Diskettes/Diskette_handling.html |url-status=dead }}</ref> However, the capacity was also quoted "1.2&nbsp;MB",<ref>{{Cite web |title=Floppy disk storage {{!}} IBM |url=https://www.ibm.com/history/floppy-disk#1970s+high-density+storage |access-date=2024-12-14 |website=www.ibm.com |language=en}}</ref> which was a hybrid decimal and binary notation, since the "M" meant 1000 × 1024. The precise value was {{val|1.2288|u=MB}} (decimal) or {{val|1.171875|u=MiB}} (binary).

The 5.25-inch [[Disk II|Apple Disk II]] had 256 bytes per sector, 13 sectors per track, 35 tracks per side, or a total capacity of {{val|116480}} bytes. It was later upgraded to 16 sectors per track, giving a total of {{nowrap|140 × 2<sup>10</sup>}} = {{val|143360}} bytes, which was described as "140KB" using the binary sense of "K".

The most recent version of the physical hardware, the "3.5-inch diskette" cartridge, had 720 512-byte blocks (single-sided). Since two blocks comprised 1024 bytes, the capacity was quoted "360&nbsp;KB", with the binary sense of "K". On the other hand, the quoted capacity of "1.44&nbsp;MB" of the High Density ("HD") version was again a hybrid decimal and binary notation, since it meant 1440 pairs of 512-byte sectors, or {{nowrap|1440 × 2<sup>10</sup>}} = {{val|1474560|u=bytes}}. Some operating systems displayed the capacity of those disks using the binary sense of "MB", as "1.4&nbsp;MB" (which would be {{nowrap|1.4 × 2<sup>20</sup>}} ≈ {{val|1468000|u=bytes}}). User complaints forced both Apple{{citation needed|date=August 2023}} and Microsoft<ref name="msoftxxxx" /> to issue support bulletins explaining the discrepancy.

==== Optical disks ====
When specifying the capacities of optical [[compact disc]]s, "megabyte" and "MB" usually meant 1024<sup>2</sup>&nbsp;bytes. Thus a "700-MB" (or "80-minute") CD has a nominal capacity of about {{val|700|u=MiB}}, which is approximately {{val|730|u=MB}} (decimal).<ref name="cdromcap" />

On the other hand, capacities of other [[optical disc]] storage media like [[DVD]], [[Blu-ray Disc]], [[HD DVD]] and [[Magneto-optical drive|magneto-optical (MO)]] have been generally specified in decimal gigabytes ("GB"), that is, 1000<sup>3</sup> bytes. In particular, a typical "{{val|4.7|u=GB}}" DVD has a nominal capacity of about {{val|4.7|e=9|u=bytes}}, which is about {{val|4.38|u=GiB}}.<ref name="dvdcap" />

==== Tape drives and media ====
Tape drive and media manufacturers have generally used SI decimal prefixes to specify the maximum capacity,<ref name="IBMt2016" /><ref name="ECMA2013" /> although the actual capacity would depend on the [[block (data storage)|block size]] used when recording.

==== Data and clock rates ====
Computer [[Clock signal|clock]] frequencies are always quoted using SI prefixes in their decimal sense. For example, the internal clock frequency of the original [[IBM PC]] was {{val|4.77|u=MHz}}, that is {{val|4770000|u=Hz}}.

Similarly, digital information transfer rates are quoted using decimal prefixe. The [[Parallel ATA]] "{{val|100|u=MB/s}}" disk interface can transfer {{val|100000000}} bytes per second, and a "{{val|56|u=Kb/s}}" modem transmits {{val|56000}} bits per second. Seagate specified the sustained transfer rate of some hard disk drive models with both decimal and IEC binary prefixes.<ref name="seaga2011" /> 
The standard sampling rate of music [[compact disk]]s, quoted as {{val|44.1|u=kHz}}, is indeed {{val|44100}} samples per second.{{citation needed|date=August 2023}} A "{{val|1|u=Gb/s}}" [[Ethernet]] interface can receive or transmit up to 10<sup>9</sup> bits per second, or {{val|125000000}} bytes per second within each packet. A "[[56k]]" modem can encode or decode up to {{val|56000}} bits per second.

Decimal SI prefixes are also generally used for [[computer bus|processor-memory data transfer]] speeds. A [[PCI-X]] bus with {{val|66|u=MHz}} clock and 64 bits wide can transfer {{val|66000000}} 64-bit words per second, or {{val|4224000000|u=bit/s}} = {{val|528000000|u=B/s}}, which is usually quoted as {{val|528|u=MB/s}}. A [[DDR SDRAM|PC3200]] memory on a [[double data rate]] bus, transferring 8 bytes per cycle with a clock speed of {{val|200|u=MHz}} has a bandwidth of {{nowrap|{{val|200000000}} × 8 × 2}} = {{val|3200000000|u=B/s}}, which would be quoted as {{val|3.2|u=GB/s}}.

=== Ambiguous standards ===
The ambiguous usage of the prefixes "kilo ("K" or "k"), "mega" ("M"), and "giga" ("G"), as meaning both powers of 1000 or (in computer contexts) of 1024, has been recorded in popular dictionaries,<ref name="webster" /><ref name="metadict" /><ref name="oxford" /> and even in some obsolete standards, such as [[ANSI/IEEE 1084-1986 standard|ANSI/IEEE&nbsp;1084-1986]]<ref name="ansi1986" /> and [[ANSI/IEEE 1212-1991 standard|ANSI/IEEE&nbsp;1212-1991]],<ref name="ieee1992" /> [[IEEE 610.10-1994 standard|IEEE&nbsp;610.10-1994]],<ref name="ieee1994" /> and [[IEEE 100-2000 standard|IEEE&nbsp;100-2000]].<ref name="ieee2000" /> Some of these standards specifically limited the binary meaning to multiples of "byte" ("B") or "bit" ("b").

=== Early binary prefix proposals ===
Before the IEC standard, several alternative proposals existed for unique binary prefixes, starting in the late 1960s. In 1996, [[Markus Kuhn (computer scientist)|Markus Kuhn]] proposed the extra prefix "di" and the symbol [[suffix]] or [[subscript]] "2" to mean "binary"; so that, for example, "one dikilobyte" would mean "1024 bytes", denoted "K<sub>2</sub>B" or "K2B".<ref name="kuhn1996" />

In 1968, Donald Morrison proposed to use the Greek letter kappa ([[κ]]) to denote 1024, κ<sup>2</sup> to denote 1024<sup>2</sup>, and so on.<ref name="morr1968" /> (At the time, memory size was small, and only K was in widespread use.) In the same year, [[Wallace Givens]] responded with a suggestion to use bK as an abbreviation for 1024 and bK2 or bK<sup>2</sup> for 1024<sup>2</sup>, though he noted that neither the Greek letter nor lowercase letter b would be easy to reproduce on computer printers of the day.<ref name="give1968" /> [[Bruce Alan Martin]] of [[Brookhaven National Laboratory]] proposed that, instead of prefixes, binary powers of two were indicated by the letter [[binary scientific notation|B]] followed by the exponent, similar to [[E notation|E]] in [[decimal scientific notation]]. Thus one would write 3B20 for {{nowrap|3 × 2<sup>20</sup>}}.<ref name="mart1968" /> This convention is still used on some calculators to present binary floating point-numbers today.<ref name="schw1993" />

In 1969, [[Donald Knuth]], who uses decimal notation like 1&nbsp;MB = 1000&nbsp;kB,<ref name="knuth2016" /> proposed that the powers of 1024 be designated as "large kilobytes" and "large megabytes", with abbreviations KKB and MMB.<ref name="knuth1999" />

=== Consumer confusion ===
The ambiguous meanings of "kilo", "mega", "giga", etc., has caused significant [[consumer confusion]], especially in the [[personal computer]] era. A common source of confusion was the discrepancy between the capacities of hard drives specified by manufacturers, using those prefixes in the decimal sense, and the numbers reported by operating systems and other software, that used them in the binary sense, such as the [[Timeline of binary prefixes#Mac1984|Apple Macintosh]] in 1984. For example, a hard drive marketed as "1&nbsp;TB" could be reported as having only "931&nbsp;GB". The confusion was compounded by fact that RAM manufacturers used the binary sense too.

=== Legal disputes ===
The different interpretations of disk size prefixes led to class action lawsuits against digital storage manufacturers. These cases involved both flash memory and hard disk drives.

==== Early cases ====
Early cases (2004–2007) were settled prior to any court ruling with the manufacturers admitting no wrongdoing but agreeing to clarify the storage capacity of their products on the consumer packaging. Accordingly, many flash memory and hard disk manufacturers have disclosures on their packaging and web sites clarifying the formatted capacity of the devices or defining MB as 1&nbsp;million bytes and 1&nbsp;GB as 1&nbsp;billion bytes.<ref name="wdc2007" /><ref name="flash2016" /><ref name="sand2013" /><ref name="sd-cap-disclaimer" />

==== ''Willem Vroegh v. Eastman Kodak Company'' ====
On 20 February 2004, [[Vroegh v. Eastman Kodak Co.|Willem Vroegh filed a lawsuit]] against Lexar Media, Dane–Elec Memory, [[Fujifilm|Fuji Photo Film USA]], [[Eastman Kodak]] Company, Kingston Technology Company, Inc., [[Memorex]] Products, Inc.; [[PNY Technologies]] Inc., [[SanDisk|SanDisk Corporation]], [[Verbatim Corporation]], and [[Viking Interworks]] alleging that their descriptions of the capacity of their [[flash memory]] cards were false and misleading.

Vroegh claimed that a 256&nbsp;MB Flash Memory Device had only 244&nbsp;MB of accessible memory. "Plaintiffs allege that Defendants marketed the memory capacity of their products by assuming that one megabyte equals one million bytes and one gigabyte equals one billion bytes." The plaintiffs wanted the defendants to use the customary values of 1024<sup>2</sup> for megabyte and 1024<sup>3</sup> for gigabyte. The plaintiffs acknowledged that the IEC and IEEE standards define a MB as one million bytes but stated that the industry has largely ignored the IEC standards.<ref name="vreo2005" />

The parties agreed that manufacturers could continue to use the decimal definition so long as the definition was added to the packaging and web sites.<ref name="sand2012" /> The consumers could apply for "a discount of ten percent off a future online purchase from Defendants' Online Stores Flash Memory Device".<ref name="safi2007" />

==== ''Orin Safier v. Western Digital Corporation'' ====
On 7 July 2005, an action entitled ''Orin Safier v. [[Western Digital]] 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 subsequently moved to the Northern District of California, Case No. 05-03353 BZ.<ref name="gutr2006" />

Although Western Digital maintained that their usage of units is consistent with "the indisputably correct industry standard for measuring and describing storage capacity", and that they "cannot be expected to reform the software industry", they agreed to settle in March 2006 with 14 June 2006 as the Final Approval hearing date.<ref name="zimm2006" />

Western Digital offered to compensate customers with a [[Gratis versus libre#Gratis|gratis]] download of backup and recovery software that they valued at US$30. They also paid {{val|p=$|500000}} in fees and expenses to San Francisco lawyers Adam Gutride and Seth Safier, who filed the suit. The settlement called for Western Digital to add a disclaimer to their later packaging and advertising.<ref name="betaxxxx" /><ref name="reim2006" /><ref name="wdc2010" />
<!--- I think that to end on this bit is overly POV. I'll leave it to someone else to add. – jeh--->
Western Digital had this footnote in their settlement. "Apparently, Plaintiff believes that he could sue an egg company for fraud for labeling a carton of 12 eggs a 'dozen', because some bakers would view a 'dozen' as including 13 items."<ref name="bask2006" />

==== ''Cho v. Seagate Technology (US) Holdings, Inc.'' ====
A lawsuit (''Cho v. Seagate Technology (US) Holdings, Inc.'', San Francisco Superior Court, Case No. CGC-06-453195) was filed against [[Seagate Technology]], alleging that Seagate overrepresented the amount of usable storage by 7% on hard drives sold between 22 March 2001 and 26 September 2007. The case was settled without Seagate admitting wrongdoing, but agreeing to supply those purchasers with gratis backup software or a 5% refund on the cost of the drives.<ref name="seagb2011" />

==== ''Dinan et al. v. SanDisk LLC'' ====
On 22 January 2020, the district court of the Northern District of California ruled in favor of the defendant, [[SanDisk]], upholding its use of "GB" to mean {{val|1000000000|u=bytes}}.<ref name="suitbxxxx" />

=== IEC 1999 Standard ===
In 1995, the [[International Union of Pure and Applied Chemistry]]'s (IUPAC) Interdivisional Committee on Nomenclature and Symbols (IDCNS) proposed the prefixes "kibi" (short for "kilobinary"), "mebi" ("megabinary"), "gibi" ("gigabinary") and "tebi" ("terabinary"), with respective symbols "kb", "Mb", "Gb" and "Tb",<ref name="iucr1995" /> for binary multipliers. The proposal suggested that the SI prefixes should be used only for powers of 10; so that a disk drive capacity of "500 gigabytes", "0.5 terabytes", "500&nbsp;GB", or "0.5&nbsp;TB" should all mean {{val|500|e=9|u=bytes}}, exactly or approximately, rather than {{nowrap|500 × 2<sup>30</sup>}} (=&nbsp;{{val|536870912000}}) or {{nowrap|0.5 × 2<sup>40</sup>}} (=&nbsp;{{val|549755813888}}).

The proposal was not accepted by IUPAC at the time, but was taken up in 1996 by the [[Institute of Electrical and Electronics Engineers]] (IEEE) in collaboration with the [[International Organization for Standardization]] (ISO) and [[International Electrotechnical Commission]] (IEC). The prefixes "kibi", "mebi", "gibi" and "tebi" were retained, but with the symbols "Ki" (with capital "K"), "Mi", "Gi" and "Ti" respectively.<ref name="iucr1996" /><!-- The preceding reference is weak as it merely consists of IUPAC noting IEC's proposal, but it is apparently the only thing we have. Would be better to have a ref for the actual proposal -->

In January 1999, the IEC published this proposal, with additional prefixes "pebi" ("Pi") and "exbi" ("Ei"), as an international standard ([[IEC 60027-2]] Amendment 2)<ref name="iec1999" /><!--- the preceding reference really needs more than just a quote. From what is it quoting? ---><ref name="iucr1999" /><!--- this reference is weak as it merely consists of the International Union of Crystallography reporting on IUPAC's reporting on the IEC standard(!) ---><ref name="IEC2000" /> The standard reaffirmed the BIPM's position that the SI prefixes should always denote powers of 10. The third edition of the standard, published in 2005, added prefixes "zebi" and "yobi", thus matching all then-defined SI prefixes with binary counterparts.<ref name="iec2005" />

The harmonized [[International Organization for Standardization|ISO]]/[[International Electrotechnical Commission|IEC]] [[IEC 80000-13]]:2025 standard cancels and replaces subclauses 3.8 and 3.9 of IEC 60027-2:2005 (those defining prefixes for binary multiples). The only significant change is the addition of explicit definitions for some quantities.<ref name="niso2008" /><!--- once again, a link to a cite to the document, not to the actual ISO/IEC document. This is unavoidable as the documents in question are *not* freely available ---> In 2009, the prefixes kibi-, mebi-, etc. were defined by [[ISO 80000-1]] in their own right, independently of the kibibyte, mebibyte, and so on.

The BIPM standard JCGM 200:2012 "International vocabulary of metrology – Basic and general concepts and associated terms (VIM), 3rd edition" lists the IEC binary prefixes and states "SI prefixes refer strictly to powers of 10, and should not be used for powers of 2. For example, 1 kilobit should not be used to represent {{val|1024}} bits (2<sup>10</sup>&nbsp;bits), which is 1 kibibit."<ref name="jcgm2012" />

The IEC 60027-2 standard recommended operating systems and other software were updated to use binary or decimal prefixes consistently, but incorrect usage of SI prefixes for binary multiples is still common. At the time, the IEEE decided that their standards would use the prefixes "kilo", etc. with their metric definitions, but allowed the binary definitions to be used in an interim period as long as such usage was explicitly pointed out on a case-by-case basis.<ref name="barr1997" />

==== Other standards bodies and organizations ====
The IEC standard binary prefixes are supported by other standardization bodies and technical organizations.

The United States [[National Institute of Standards and Technology]] (NIST) supports the ISO/IEC standards for
"Prefixes for binary multiples" and has a web page<ref name="NISTbin" /> documenting them, describing and justifying their use. NIST suggests that in English, the first syllable of the name of the binary-multiple prefix should be pronounced in the same way as the first syllable of the name of the corresponding SI prefix, and that the second syllable should be pronounced as ''bee''.<ref name="NIST2" /> NIST has stated the SI prefixes "refer strictly to powers of 10" and that the binary definitions "should not be used" for them.<ref name="taylo2008" />

As of 2014, the microelectronics industry standards body [[JEDEC]] describes the IEC prefixes in its online dictionary, but acknowledges that the SI prefixes and the symbols "K", "M" and "G" are still commonly used with the binary sense for memory sizes.<ref name="jedec2021" /><ref name="JEDEC2014" />

On 19 March 2005, the IEEE standard [[IEEE 1541-2002]] ("Prefixes for Binary Multiples") was elevated to a full-use standard by the IEEE Standards Association after a two-year trial period.<ref name="IEEE2003" /><ref name="IEEE2005" /> {{As of|2008|4|lc=on}}, the IEEE Publications division does not require the use of IEC prefixes in its major magazines such as ''Spectrum''<ref name="walli2008" /> or ''Computer''.<ref name ="gesch2007">{{Cite journal |last1=Gschwind |first1=Michael |title=An Open Source Environment for Cell Broadband Engine System Software |journal=Computer |volume=40 |issue=6 |pages=37–47 |publisher=IEEE Computer Society |date=June 2007 |doi = 10.1109/MC.2007.192 |last2=Erb |first2=David |last3=Manning |first3=Sid |last4=Nutter |first4=Mark |s2cid=10877922 |url=http://www.research.ibm.com/people/m/mikeg/papers/2007_ieeecomputer.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.research.ibm.com/people/m/mikeg/papers/2007_ieeecomputer.pdf |archive-date=2022-10-09 |url-status=live }} "The processor has a memory subsystem with separate first-level 32-Kbyte instruction and data caches, and a 512-Kbyte unified second-level cache." Authors are with IBM.</ref> <!-- and many of the IEEE technical journals allow the authors to select the units in their papers.{{Citation needed|date=May 2008}}-->

The [[International Bureau of Weights and Measures]] (BIPM), which maintains the [[International System of Units]] (SI), expressly prohibits the use of SI prefixes to denote binary multiples, and recommends the use of the IEC prefixes as an alternative since units of information are not included in the SI.<ref name="BIPM8web" /><ref name="BIPM8" />

The [[SAE International|Society of Automotive Engineers]] (SAE) prohibits the use of SI prefixes with anything but a power-of-1000 meaning, but does not cite the IEC binary prefixes.<ref name="SAE2017" />

The European Committee for Electrotechnical Standardization ([[CENELEC]]) adopted the IEC-recommended binary prefixes via the harmonization document HD&nbsp;60027-2:2003-03.<ref name="CENELEC2003" /> The European Union (EU) has required the use of the IEC binary prefixes since 2007.<ref name="CENELECxxxx" />

=== Current practice ===
[[File:Elixir M2U51264DS8HC3G-5T 20060320.jpg|left|thumb|The {{val|536870912}}-byte capacity of these RAM modules is stated as "512&nbsp;MB" on the label.]]
[[File:GParted 0.3.5 -- 2008, 06.png|right|thumb|[[GNOME]]'s partition editor uses IEC prefixes to display partition sizes. The total capacity of the 120&nbsp;×&nbsp;10<sup>9</sup>-byte disk is displayed as "111.79&nbsp;GiB".]]
[[File:GNOME System Monitor memory size and network rate.png|right|thumb|GNOME's system monitor uses IEC prefixes to show memory size and networking data rate.]]

Some computer industry participants, such as Hewlett-Packard (HP),<ref name="hpen2009" /> and IBM<ref name="resp2011" /><ref name="IBMaxxxx" /> have adopted or recommended IEC binary prefixes as part of their general documentation policies.

As of 2023, the use of SI prefixes with the binary meanings is still prevalent for specifying the capacity of the [[main memory]] of computers, of [[random access memory|RAM]], [[read-only memory|ROM]], [[EPROM]], and [[EEPROM]] [[semiconductor chip|chips]] and [[memory module]]s, and of the [[cache memory|cache]] of [[computer processor]]s.  For example, a "512-megabyte" or "512&nbsp;MB" memory module holds 512&nbsp;MiB; that is, 512&nbsp;×&nbsp;2<sup>20</sup> bytes, not 512&nbsp;×&nbsp;10<sup>6</sup> bytes.<ref name="customxxxx" /><ref name="HP2012" /><ref name="sony2017" /><ref name="forall2012" />

JEDEC continues to include the customary binary definitions of "kilo", "mega", and "giga" in the document ''Terms, Definitions, and Letter Symbols'',<ref name="JEDEC-terms" /> and, {{as of|2010|lc=yes}}, still used those definitions in their [[JEDEC memory standards|memory standards]].<ref name="JEDEC-ddr3" /><ref name="JEDEC-ddr2" /><ref name="JEDEC-configs" /><ref name="JEDEC-configs-toc" /><ref name="JEDEC-configs-terms" />

On the other hand, the SI prefixes with powers of ten meanings are generally used for the capacity of external storage units, such as [[disk drives]],<ref name="hita2009" /><ref name="sams2011" /><ref name="seag2017" /><ref name="toshi2009" /><ref name="WDC2005" /> [[solid state drives]], and [[USB flash drives]],<ref name="sd-cap-disclaimer" /> except for some [[flash memory]] chips intended to be used as [[EEPROM]]s. However, some disk manufacturers have used the IEC prefixes to avoid confusion.<ref name="toshi2017" /> The decimal meaning of SI prefixes is usually also intended in measurements of data transfer rates, and clock speeds.{{citation needed|date=August 2023}}

Some operating systems and other software use either the IEC binary multiplier symbols ("Ki", "Mi", etc.)<ref name="linux2001" /><ref name="ESR2012" /><ref name="ubuntu2012" /><ref name="ubuntu2012b" /><ref name="snow2009" /><ref name="apple2018" /> or the SI multiplier symbols ("k", "M", "G", etc.) with decimal meaning. Some programs, such as the [[GNU]] [[ls]] command, let the user choose between binary or decimal multipliers. However, some continue to use the SI symbols with the binary meanings, even when reporting disk or file sizes. Some programs may also use "K" instead of "k", with either meaning.<ref>{{cite web | url=https://man7.org/linux/man-pages/man1/ls.1.html | title=Ls(1) – Linux manual page }}</ref>