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90-423: A binary prefix is a unit prefix that indicates a multiple of a unit of measurement by an integer power of two . The most commonly used binary prefixes are kibi (symbol Ki, meaning 2 = 1024 ), mebi ( Mi, 2 = 1 048 576 ), and gibi ( Gi, 2 = 1 073 741 824 ). They are most often used in information technology as multipliers of bit and byte , when expressing the capacity of storage devices or

180-707: A non-serious fashion , in May 2010. Ian Mills, president of the Consultative Committee on Units, considered the chances of official adoption to be remote. The prefix geop and term "geopbyte" have been used in the information technology industry to refer to 10 bytes, following "brontobyte". The ascending prefixes peta ( 1000 ) and exa ( 1000 ) are based on the Greek-derived numeric prefixes "penta" (5) and "hexa" (6). The largest prefixes zetta ( 1000 ), and yotta ( 1000 ) and, similarly,

270-408: A " μ " key, so it is necessary to use a key-code; this varies depending on the operating system, physical keyboard layout, and user's language. The LaTeX typesetting system features an SIunitx package in which the units of measurement are spelled out, for example, \qty{3}{\tera\hertz} formats as "3 THz". The use of prefixes can be traced back to the introduction of the metric system in

360-409: A disclaimer to their later packaging and advertising. 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." A lawsuit ( Cho v. Seagate Technology (US) Holdings, Inc. , San Francisco Superior Court, Case No. CGC-06-453195)

450-585: A driver, in order to maintain symmetry. The prefixes from tera- to quetta- are based on the Ancient Greek or Ancient Latin numbers from 4 to 10, referring to the 4th through 10th powers of 10 . The initial letter h has been removed from some of these stems and the initial letters z , y , r , and q have been added, ascending in reverse alphabetical order, to avoid confusion with other metric prefixes. When mega and micro were adopted in 1873, there were then three prefixes starting with "m", so it

540-506: A few unofficial prefixes appeared on the Internet: hepa (10 ), ento (10 ), otta (10 ), fito (10 ), nea (10 ), syto (10 ), dea (10 ), tredo (10 ), una (10 ) and revo (10 ). The Oxford professor Jeffrey K. Aronson has suggested extending beyond zetta/zepto and yotta/yocto with xenta/xenno , wekta/weko , vendeka/vendeko , and udeka/udeko , based on the idea that the "Z" and "Y" prefixes would continue backwards through

630-420: A given unit has often arisen by convenience of use and historical developments. Unit prefixes that are much larger or smaller than encountered in practice are seldom used, albeit valid combinations. In most contexts only a few, the most common, combinations are established. For example, prefixes for multiples greater than one thousand are rarely applied to the gram or metre. Some prefixes used in older versions of

720-448: A little more than that, but less than 10 × 2 = 10 737 418 240 and a file whose size is listed as "2.3 GB" may have a size closer to 2.3 × 2 ≈ 2 470 000 000 or to 2.3 × 10 = 2 300 000 000 , depending on the program or operating system providing that measurement. This kind of ambiguity is often confusing to computer system users and has resulted in lawsuits . The IEC 60027-2 binary prefixes have been incorporated in

810-460: A number of definitions for the non-SI unit, the calorie . There are gram calories and kilogram calories. One kilogram calorie, which equals one thousand gram calories, often appears capitalised and without a prefix (i.e. Cal ) when referring to " dietary calories " in food. It is common to apply metric prefixes to the gram calorie, but not to the kilogram calorie: thus, 1 kcal = 1000 cal = 1 Cal. Metric prefixes are widely used outside

900-483: A reintroduction of compound prefixes (e.g. kiloquetta- for 10 ) if a driver for prefixes at such scales ever materialises, with a restriction that the last prefix must always be quetta- or quecto- . This usage has not been approved by the BIPM. In written English, the symbol K is often used informally to indicate a multiple of thousand in many contexts. For example, one may talk of a 40K salary ( 40 000 ), or call

990-404: A total capacity of 116 480 bytes. It was later upgraded to 16 sectors per track, giving a total of 140 × 2 = 143 360 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 KB", with

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1080-413: A typical " 4.7 GB " DVD has a nominal capacity of about 4.7 × 10 bytes , which is about 4.38 GiB . Tape drive and media manufacturers have generally used SI decimal prefixes to specify the maximum capacity, although the actual capacity would depend on the block size used when recording. Computer clock frequencies are always quoted using SI prefixes in their decimal sense. For example,

1170-464: 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 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. The 5.25-inch diskette sold with

1260-482: Is 1 kibibit." 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

1350-488: Is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic . Each prefix has a unique symbol that is prepended to any unit symbol. The prefix kilo- , for example, may be added to gram to indicate multiplication by one thousand: one kilogram is equal to one thousand grams. The prefix milli- , likewise, may be added to metre to indicate division by one thousand; one millimetre

1440-662: Is equal to one thousandth of a metre. Decimal multiplicative prefixes have been a feature of all forms of the metric system , with six of these dating back to the system's introduction in the 1790s. Metric prefixes have also been used with some non-metric units. The SI prefixes are metric prefixes that were standardised for use in the International System of Units (SI) by the International Bureau of Weights and Measures (BIPM) in resolutions dating from 1960 to 2022. Since 2009, they have formed part of

1530-437: Is formed from the first syllable of the decimal prefix with the similar value, and the syllable "bi". The symbols are the decimal symbol, always capitalised, followed by the letter "i". According to these standards, kilo , mega , giga , et seq. should only be used in the decimal sense, even when referring to data storage capacities: kilobyte and megabyte denote one thousand and one million bytes respectively (consistent with

1620-521: Is indeed 44 100 samples per second. A " 1 Gb/s " Ethernet interface can receive or transmit up to 10 bits per second, or 125 000 000 bytes per second within each packet. A " 56k " modem can encode or decode up to 56 000 bits per second. Decimal SI prefixes are also generally used for processor-memory data transfer speeds. A PCI-X bus with 66 MHz clock and 64 bits wide can transfer 66 000 000 64-bit words per second, or 4 224 000 000  bit/s = 528 000 000  B/s , which

1710-609: Is the addition of explicit definitions for some quantities. 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 1024 bits (2 bits), which

1800-672: Is usually quoted as 528  MB/s . A PC3200 memory on a double data rate bus, transferring 8 bytes per cycle with a clock speed of 200 MHz has a bandwidth of 200 000 000 × 8 × 2 = 3 200 000 000  B/s , which would be quoted as 3.2  GB/s . 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, and even in some obsolete standards, such as ANSI/IEEE 1084-1986 and ANSI/IEEE 1212-1991 , IEEE 610.10-1994 , and IEEE 100-2000 . Some of these standards specifically limited

1890-511: The IBM PC AT could hold 1200 × 1024 = 1 228 800 bytes, and thus was marketed as "1200 KB" with the binary sense of "KB". However, the capacity was also quoted "1.2 MB", which was a hybrid decimal and binary notation, since the "M" meant 1000 × 1024. The precise value was 1.2288 MB (decimal) or 1.171 875  MiB (binary). The 5.25-inch Apple Disk II had 256 bytes per sector, 13 sectors per track, 35 tracks per side, or

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1980-789: The ISO/IEC 80000 standard and are supported by other standards bodies, including the BIPM , which defines the SI system, the US NIST , and the European Union . Prior to the 1999 IEC standard, some industry organizations, such as the Joint Electron Device Engineering Council (JEDEC), attempted to redefine the terms kilobyte , megabyte , and gigabyte , and the corresponding symbols KB , MB , and GB in

2070-679: The ISO/IEC 80000 standard. They are also used in the Unified Code for Units of Measure (UCUM). The BIPM specifies twenty-four prefixes for the International System of Units (SI) . The first uses of prefixes in SI date back to the definition of kilogram after the French Revolution at the end of the 18th century. Several more prefixes came into use, and were recognised by the 1947 IUPAC 14th International Conference of Chemistry before being officially adopted for

2160-525: 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. 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) The standard reaffirmed

2250-568: The International System of Units (SI). In addition to those listed in the everyday-use table, the SI includes standardised prefixes for 10 ( peta ), 10 ( exa ), 10 ( zetta ), 10 ( yotta ), 10 ( ronna ), and 10 ( quetta ); and for 10 ( femto ), 10 ( atto ), 10 (zepto), 10 ( yocto ), 10 ( ronto ), and 10 ( quecto ). Although formerly in use, the SI disallows combining prefixes; the * microkilogram or * centimillimetre , for example, are not permitted. Prefixes corresponding to powers of one thousand are usually preferred, however, units such as

2340-505: The SI prefixes were internationally adopted by the 11th CGPM conference in 1960. Early computers used one of two addressing methods to access the system memory; binary (base 2) or decimal (base 10). For example, the IBM 701 (1952) used a binary methods and could address 2048 words of 36 bits each, while the IBM 702 (1953) used a decimal system, and could address ten thousand 7-bit words. By

2430-653: The Year 2000 problem the Y2K problem . In these cases, an uppercase K is often used with an implied unit (although it could then be confused with the symbol for the kelvin temperature unit if the context is unclear). This informal postfix is read or spoken as "thousand", "grand", or just "k". The financial and general news media mostly use m or M, b or B, and t or T as abbreviations for million, billion (10 ) and trillion (10 ), respectively, for large quantities, typically currency and population. The medical and automotive fields in

2520-495: The byte . Units of information are not covered in the International System of Units. Computer professionals have historically used the same spelling, pronunciation and symbols for the binary series in the description of computer memory , although the symbol for kilo is often capitalised. For example, in citations of main memory or RAM capacity, kilobyte , megabyte and gigabyte customarily mean 1024 (2 ), 1 048 576 (2 ) and 1 073 741 824 (2 ) bytes respectively. In

2610-503: 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 Apple Macintosh in 1984. For example, a hard drive marketed as "1 TB" could be reported as having only "931 GB". The confusion

2700-534: The year , equal to exactly 31 557 600  seconds ( ⁠365 + 1  / 4 ⁠  days). The unit is so named because it was the average length of a year in the Julian calendar . Long time periods are then expressed by using metric prefixes with the annum, such as megaannum (Ma) or gigaannum (Ga). The SI unit of angle is the radian , but degrees , as well as arc-minutes and arc-seconds , see some scientific use. Common practice does not typically use

2790-437: The 11th CGPM conference in 1960. Other metric prefixes used historically include hebdo- (10 ) and micri- (10 ). Double prefixes have been used in the past, such as micromillimetres or millimicrons (now nanometres ), micromicrofarads (μμF; now picofarads , pF), kilomegatonnes (now gigatonnes ), hectokilometres (now 100  kilometres ) and the derived adjective hectokilometric (typically used for qualifying

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2880-619: The 1790s, long before the 1960 introduction of the SI. The prefixes, including those introduced after 1960, are used with any metric unit, whether officially included in the SI or not (e.g., millidyne and milligauss). Metric prefixes may also be used with some non-metric units, but not, for example, with the non-SI units of time. The units kilogram , gram , milligram , microgram, and smaller are commonly used for measurement of mass . However, megagram, gigagram, and larger are rarely used; tonnes (and kilotonnes, megatonnes, etc.) or scientific notation are used instead. The megagram does not share

2970-430: 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. The harmonized ISO / IEC IEC 80000-13 :2008 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

3060-559: The English alphabet. He goes on to list a large number of prefixes, starting with Xona, Weka, Vunda, Uda, Treda, Sorta , ... Another proposal for xenta/xona is novetta , from the Italian "nove" (or "nine"). In 1993, Morgan Burke proposed, as a joke, harpo for 10 , groucho for 10 (and therefore harpi for 10 , grouchi for 10 , zeppi for 10 , gummi for 10 , and chici for 10 ). Double (metric prefix) A metric prefix

3150-582: The Greek letter kappa ( κ ) to denote 1024, κ to denote 1024, and so on. (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 for 1024, though he noted that neither the Greek letter nor lowercase letter b would be easy to reproduce on computer printers of the day. Bruce Alan Martin of Brookhaven National Laboratory proposed that, instead of prefixes, binary powers of two were indicated by

3240-563: The IEC and IEEE standards define a MB as one million bytes but stated that the industry has largely ignored the IEC standards. 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. The consumers could apply for "a discount of ten percent off a future online purchase from Defendants' Online Stores Flash Memory Device". On 7 July 2005, an action entitled Orin Safier v. Western Digital Corporation, et al.

3330-591: The Latin annus ), is commonly used with metric prefixes: ka , Ma, and Ga. Official policies about the use of SI prefixes with non-SI units vary slightly between the International Bureau of Weights and Measures (BIPM) and the American National Institute of Standards and Technology (NIST). For instance, the NIST advises that "to avoid confusion, prefix symbols (and prefix names) are not used with

3420-536: The SI prefixes should be used only for powers of 10; so that a disk drive capacity of "500 gigabytes", "0.5 terabytes", "500 GB", or "0.5 TB" should all mean 500 × 10 bytes , exactly or approximately, rather than 500 × 2 (=  536 870 912 000 ) or 0.5 × 2 (=  549 755 813 888 ). 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

3510-484: The United States use the abbreviations cc or ccm for cubic centimetres. One  cubic centimetre is equal to one  millilitre . For nearly a century, engineers used the abbreviation MCM to designate a "thousand circular mils " in specifying the cross-sectional area of large electrical cables . Since the mid-1990s, kcmil has been adopted as the official designation of a thousand circular mils, but

3600-404: The astronomical unit is mentioned in the SI standards as an accepted non-SI unit. Prefixes for the SI standard unit second are most commonly encountered for quantities less than one second. For larger quantities, the system of minutes (60 seconds), hours (60 minutes) and days (24 hours) is accepted for use with the SI and more commonly used. When speaking of spans of time,

3690-434: The binary meaning to multiples of "byte" ("B") or "bit" ("b"). Before the IEC standard, several alternative proposals existed for unique binary prefixes, starting in the late 1960s. In 1996, 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 2 B" or "K2B". In 1968, Donald Morrison proposed to use

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3780-710: The binary rather than decimal meaning. This convention, which could not be extended to higher powers, was widely used in the documentation of the IBM ;360 (1964) and of the IBM System/370 (1972), of the CDC ;7600 , of the DEC PDP-11 /70 (1975) and of the DEC VAX-11/780 (1977). In other documents, however, the metric prefixes and their symbols were used to denote powers of 10, but usually with

3870-565: The binary sense of "K". On the other hand, the quoted capacity of "1.44 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 1440 × 2 = 1 474 560  bytes . Some operating systems displayed the capacity of those disks using the binary sense of "MB", as "1.4 MB" (which would be 1.4 × 2 ≈ 1 468 000  bytes ). User complaints forced both Apple and Microsoft to issue support bulletins explaining

3960-402: The binary sense, for use in storage capacity measurements. However, other computer industry sectors (such as magnetic storage ) continued using those same terms and symbols with the decimal meaning. Since then, the major standards organizations have expressly disapproved the use of SI prefixes to denote binary multiples, and recommended or mandated the use of the IEC prefixes for that purpose, but

4050-654: 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 13 030 -byte block in each of its 808 × 19 tracks. Decimal megabytes were used for disk capacity by the CDC in 1974. The Seagate ST-412 , one of several types installed in the IBM PC/XT , had a capacity of 10 027 008  bytes when formatted as 306 × 4 tracks and 32 256-byte sectors per track, which

4140-586: The capacity of a "10 MB" (decimal "M") disk drive could be reported as " 9.56 MB ", and that of a "300 GB" drive as "279.4 GB". Some operating systems, such as Mac OS X , Ubuntu , and Debian , 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. Floppy disks used

4230-447: 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 50 000 sectors of 100 characters each, for a total quoted capacity of 5 million characters. Moreover, since the 1960s, many disk drives used IBM's disk format , where each track was divided into blocks of user-specified size; and

4320-491: The capacity of their flash memory cards were false and misleading. Vroegh claimed that a 256 MB Flash Memory Device had only 244 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 for megabyte and 1024 for gigabyte. The plaintiffs acknowledged that

4410-419: The computer industry to indicate the nearest powers of two. For example, a memory module whose capacity was specified by the manufacturer as "2 megabytes" or "2 MB" would hold 2 × 2 = 2 097 152 bytes , instead of 2 × 10 = 2 000 000 . On the other hand, a hard disk whose capacity is specified by the manufacturer as "10 gigabytes" or "10 GB", holds 10 × 10 = 10 000 000 000 bytes, or

4500-594: 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 million bytes and 1 GB as 1 billion bytes. On 20 February 2004, Willem Vroegh filed a lawsuit against 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

4590-527: The defendant, SanDisk, upholding its use of "GB" to mean 1 000 000 000  bytes . 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", for binary multipliers. The proposal suggested that

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4680-450: The descending prefixes zepto ( 1000 ) and yocto ( 1000 ) are derived from Latin "septem" (7) and " octo" (8) plus the initial letters "z" and "y". The initial letters "z" and "y" appear in the largest SI prefixes. They were changed because of previously proposed ascending hepto (Greek "hepta" (7)) was already in use as a numerical prefix (implying seven) and the letter "h" as both SI-accepted non-SI unit (hour) and prefix ( hecto 10 ),

4770-489: The discrepancy. When specifying the capacities of optical compact discs , "megabyte" and "MB" usually meant 1024 bytes. Thus a "700-MB" (or "80-minute") CD has a nominal capacity of about 700 MiB , which is approximately 730 MB (decimal). On the other hand, capacities of other optical disc storage media like DVD , Blu-ray Disc , HD DVD and magneto-optical (MO) have been generally specified in decimal gigabytes ("GB"), that is, 1000 bytes. In particular,

4860-432: The first time in 1960. The most recent prefixes adopted were ronna- , quetta- , ronto- , and quecto- in 2022, after a proposal from British metrologist Richard J. C. Brown. The large prefixes ronna- and quetta- were adopted in anticipation of needs for use in data science, and because unofficial prefixes that did not meet SI requirements were already circulating. The small prefixes were also added, even without such

4950-515: The flexibility allowed by official policy in the case of the degree Celsius (°C). NIST states: "Prefix symbols may be used with the unit symbol °C and prefix names may be used with the unit name degree Celsius . For example, 12 m°C (12 millidegrees Celsius) is acceptable." In practice, it is more common for prefixes to be used with the kelvin when it is desirable to denote extremely large or small absolute temperatures or temperature differences. Thus, temperatures of star interiors may be given with

5040-480: The fuel consumption measures). These are not compatible with the SI. Other obsolete double prefixes included "decimilli-" (10 ), which was contracted to "dimi-" and standardised in France up to 1961. There are no more letters of the Latin alphabet available for new prefixes (all the unused letters are already used for units). As such, Richard J.C. Brown (who proposed the prefixes adopted for 10 and 10 ) has proposed

5130-422: The hectolitre (100 litres). Larger volumes are usually denoted in kilolitres, megalitres or gigalitres, or else in cubic metres (1 cubic metre = 1 kilolitre) or cubic kilometres (1 cubic kilometre = 1 teralitre). For scientific purposes, the cubic metre is usually used. The kilometre, metre, centimetre, millimetre, and smaller units are common. The decimetre is rarely used. The micrometre is often referred to by

5220-557: The hectopascal, centimetre, and centilitre, are widely used; outside the SI, the units hectare , decibel are also common. The unit prefixes are always considered to be part of the unit, so that, e.g., in exponentiation , 1 km means one square kilometre, not one thousand square metres, and 1 cm means one cubic centimetre, not one hundredth of a cubic metre. In general, prefixes are used with any metric unit, but may also be used with non-metric units. Some combinations, however, are more common than others. The choice of prefixes for

5310-555: The internal clock frequency of the original IBM PC was 4.77 MHz , that is 4 770 000  Hz . Similarly, digital information transfer rates are quoted using decimal prefixe. The Parallel ATA " 100  MB/s " disk interface can transfer 100 000 000 bytes per second, and a " 56 Kb/s " modem transmits 56 000 bits per second. Seagate specified the sustained transfer rate of some hard disk drive models with both decimal and IEC binary prefixes. The standard sampling rate of music compact disks , quoted as 44.1 kHz ,

5400-418: The length of the day is usually standardised to 86 400  seconds so as not to create issues with the irregular leap second . Larger multiples of the second such as kiloseconds and megaseconds are occasionally encountered in scientific contexts, but are seldom used in common parlance. For long-scale scientific work, particularly in astronomy , the Julian year or annum (a) is a standardised variant of

5490-550: The letter B followed by the exponent, similar to E in decimal scientific notation . Thus one would write 3B20 for 3 × 2 . This convention is still used on some calculators to present binary floating point-numbers today. In 1969, Donald Knuth , who uses decimal notation like 1 MB = 1000 kB, proposed that the powers of 1024 be designated as "large kilobytes" and "large megabytes", with abbreviations KKB and MMB. The ambiguous meanings of "kilo", "mega", "giga", etc., has caused significant consumer confusion , especially in

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5580-434: The long-established metric system prefixes "kilo", "mega", "giga", etc., defined to be powers of 10, to mean instead the nearest powers of two; namely, 2 = 1024, 2 = 1024, 2 = 1024, etc. The corresponding metric prefix symbols ("k", "M", "G", etc.) where used with the same binary meanings. The symbol for 2 = 1024 could be written either in lower case ("k") or in uppercase ("K"). The latter was often used intentionally to indicate

5670-429: The metric SI system. Common examples include the megabyte and the decibel . Metric prefixes rarely appear with imperial or US units except in some special cases (e.g., microinch, kilofoot, kilopound ). They are also used with other specialised units used in particular fields (e.g., megaelectronvolt , gigaparsec , millibarn , kilodalton ). In astronomy, geology, and palaeontology, the year , with symbol 'a' (from

5760-404: The metric system are no longer used. The prefixes myria- , (from the Greek μύριοι , mýrioi ), double- and demi- , denoting factors of 10 000 , 2 and 1 ⁄ 2 respectively, were parts of the original metric system adopted in France in 1795, but they were not retained when the SI prefixes were agreed internationally by the 11th CGPM conference in 1960. The prefix " myrio- "

5850-647: The metric system), while terms such as kibibyte , mebibyte and gibibyte , with symbols KiB, MiB and GiB, denote 2 , 2 and 2 bytes respectively. Although some of the following unofficial prefixes appear repeated on the internet, no one is in actual use. A metric prefix myria (abbreviation "my"), for 10,000, was deprecated in 1960. Before the adoption of ronna and quetta for 10 and 10 and ronto and quecto for 10 and 10 in November 2022, many personal, and sometimes facetious, proposals for additional metric prefixes were formulated. The prefix bronto , as used in

5940-554: 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 lines 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 16 384 units (usually words , bytes, or bits), computer professionals also started using

6030-453: The older non-SI name micron , which is officially deprecated. In some fields, such as chemistry , the ångström (0.1 nm) has been used commonly instead of the nanometre. The femtometre , used mainly in particle physics, is sometimes called a fermi . For large scales, megametre, gigametre, and larger are rarely used. Instead, ad hoc non-metric units are used, such as the solar radius , astronomical units , light years , and parsecs ;

6120-423: The prefixes formerly used in the metric system have fallen into disuse and were not adopted into the SI. The decimal prefix for ten thousand, myria- (sometimes spelt myrio- ), and the early binary prefixes double- (2×) and demi- ( ⁠ 1 / 2 ⁠ ×) were parts of the original metric system adopted by France in 1795, but were not retained when the SI prefixes were internationally adopted by

6210-477: The risk of confusion that the tonne has with other units with the name "ton". The kilogram is the only coherent unit of the International System of Units that includes a metric prefix. The litre (equal to a cubic decimetre), millilitre (equal to a cubic centimetre), microlitre, and smaller are common. In Europe, the centilitre is often used for liquids, and the decilitre is used less frequently. Bulk agricultural products, such as grain, beer and wine, often use

6300-704: The same applied to "s" from previously proposed descending septo (i.e. SI unit "s", seconds), while "o" for octo was problematic since a symbol "o" could be confused with zero. Before the adoption of new prefixes in 2022, several personal proposals had been made for extending the series of prefixes, with ascending terms such as xenna , weka , vendeka (from Greek "ennea" (9), "deka" (10), "endeka" (11)) and descending terms such as xono , weco , vundo (from Latin "novem"/"nona" (9), "decem" (10), "undecim" (11)). Using Greek for ascending and Latin for descending would be consistent with established prefixes such as deca , hecto , kilo vs. deci , centi , milli . In 2001,

6390-406: The same time, sometimes by the same company. The HP 3000 business computer (1973) could have "64K", "96K", or "128K" bytes of memory. 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,

6480-523: The seller. (see Orin Safier v. Western Digital Corporation and Cho v. Seagate Technology (US) Holdings, Inc. ). To protect themselves, some sellers write out the full term as " 1 000 000 ". With the aim of avoiding ambiguity the International Electrotechnical Commission (IEC) adopted new binary prefixes in 1998 ( IEC 80000-13:2008 formerly subclauses 3.8 and 3.9 of IEC 60027-2:2005 ). Each binary prefix

6570-453: The size of computer files . The binary prefixes "kibi", "mebi", etc. were defined in 1999 by the International Electrotechnical Commission (IEC), in the IEC 60027-2 standard (Amendment 2). They were meant to replace the metric (SI) decimal power prefixes, such as "kilo" ( k, 10 = 1000 ), "mega" ( M, 10 = 1 000 000 ) and "giga" ( G, 10 = 1 000 000 000 ), that were commonly used in

6660-521: The software industry", they agreed to settle in March 2006 with 14 June 2006 as the Final Approval hearing date. Western Digital offered to compensate customers with a free download of backup and recovery software valued at US$ 30. They also paid $ 500 000 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

6750-419: The specifications of hard disk drive capacities and network transmission bit rates , decimal prefixes are used. For example, a 500-gigabyte hard drive holds 500 billion bytes, and a 100-megabit-per-second Ethernet connection transfers data at 100 million bits per second. The ambiguity has led to some confusion and even lawsuits from purchasers who were expecting 2 or 2 and considered themselves shortchanged by

6840-484: The term "brontobyte", has been used to represent anything from 10 to 10 bytes, most often 10 . In 2010, an online petition sought to establish hella- as the SI prefix for 10 , a movement that began on the campus of UC Davis . The prefix, which has since appeared in the San Francisco Chronicle , Daily Telegraph , Wired and some other scientific magazines, was recognised by Google , in

6930-440: The time-related unit symbols (names) min (minute), h (hour), d (day); nor with the angle-related symbols (names) ° (degree), ′ (minute), and ″ (second)", whereas the BIPM adds information about the use of prefixes with the symbol as for arcsecond when they state: "However astronomers use milliarcsecond, which they denote mas, and microarcsecond, μas, which they use as units for measuring very small angles." Some of

7020-506: 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 512 × 1024 = 536 870 912 bytes, rather than 512 000 000 . 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

7110-556: The understanding that the values given were approximate, often truncated down. Thus, for example, a 1967 document by Control Data Corporation (CDC) abbreviated "2 = 64 × 1024 = 65 536 words" as "65K words" (rather than "64K" or "66K"), while the documentation of the HP 21MX real-time computer (1974) denoted 3 × 2 = 192 × 1024 = 196 608 as "196K" and 2 = 1 048 576 as "1M". These three possible meanings of "k" and "K" ("1024", "1000", or "approximately 1000") were used loosely around

7200-415: The unit of MK (megakelvin), and molecular cooling may be given with the unit mK (millikelvin). In use the joule and kilojoule are common, with larger multiples seen in limited contexts. In addition, the kilowatt-hour , a composite unit formed from the kilowatt and hour, is often used for electrical energy; other multiples can be formed by modifying the prefix of watt (e.g. terawatt-hour). There exist

7290-651: The use of SI prefixes in this sense has persisted in some fields. In 2022, the International Bureau of Weights and Measures (BIPM) adopted the decimal prefixes ronna for 1000 and quetta for 1000. In analogy to the existing binary prefixes, a consultation paper of the International Committee for Weights and Measures ' Consultative Committee for Units (CCU) suggested the prefixes robi ( Ri, 1024 ) and quebi ( Qi, 1024 ) for their binary counterparts, but as of 2022, no corresponding binary prefixes have been adopted. The relative difference between

7380-498: The values in the binary and decimal interpretations increases, when using the SI prefixes as the base, from 2.4% for kilo to nearly 27% for the quetta prefix. Although the prefixes ronna and quetta have been defined, as of 2022 no names have been officially assigned to the corresponding binary prefixes. The original metric system adopted by France in 1795 included two binary prefixes named double - (2×) and demi - ( ⁠ 1 / 2 ⁠ ×). However, these were not retained when

7470-410: Was an alternative spelling variant for " myria- ", as proposed by Thomas Young . A binary prefix indicates multiplication by a power of two. The tenth power of 2 (2 ) has the value 1024 , which is close to 1000 . This has prompted the use of the metric prefixes kilo , mega , and giga to also denote the powers of 1024 which is common in information technology with the unit of digital information,

7560-433: Was compounded by fact that RAM manufacturers used the binary sense too. 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 (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

7650-546: Was created, it included the " μ " symbol for micro at codepoint 0xB5 ; later, the whole of ISO 8859-1 was incorporated into the initial version of Unicode . Many fonts that support both characters render them identical, but because the micro sign and the Greek lower-case letter have different applications (normally, a Greek letter would be used with other Greek letters, but the micro sign is never used like that), some fonts render them differently, e.g. Linux Libertine and Segoe UI . Most English-language keyboards do not have

7740-566: Was explicitly pointed out on a case-by-case basis. Unit prefix The prefixes of the metric system precede a basic unit of measure to indicate a decadic multiple and fraction of a unit. Each prefix has a unique symbol that is prepended to the unit symbol. Some of the prefixes date back to the introduction of the metric system in the 1790s, but new prefixes have been added, and some have been revised. The International Bureau of Weights and Measures has standardised twenty metric prefixes in resolutions dating from 1960 to 1991 for use with

7830-510: 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 free backup software or a 5% refund on the cost of the drives. On 22 January 2020, the district court of the Northern District of California ruled in favor of

7920-525: 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. 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

8010-520: Was necessary to use some other symbol besides upper and lowercase 'm'. Eventually the Greek letter "μ" was adopted. However, with the lack of a "μ" key on most typewriters, as well as computer keyboards, various other abbreviations remained common, including "mc", "mic", and "u". From about 1960 onwards, "u" prevailed in type-written documents. Because ASCII , EBCDIC , and other common encodings lacked code-points for " μ ", this tradition remained even as computers replaced typewriters. When ISO 8859-1

8100-664: Was quoted as "10 MB". Similarly, a "300 GB" hard drive can be expected to offer only slightly more than 300 × 10 = 300 000 000 000 , bytes, not 300 × 2 (which would be about 322 × 10 bytes or "322 GB"). The first terabyte (SI prefix, 1 000 000 000 000 bytes) hard disk drive was introduced in 2007. Decimal prefixes were generally used by information processing publications when comparing hard disk capacities. 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,

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