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Kilobyte

From Wikipedia, the free encyclopedia
Multiple of the unit byte
Not to be confused withkilobit.
"KByte" redirects here. For the battery electric car from Future Mobility Corporation, seeByton K-Byte.
Multiple-byte units
Decimal
ValueMetric
1000kBkilobyte
10002MBmegabyte
10003GBgigabyte
10004TBterabyte
10005PBpetabyte
10006EBexabyte
10007ZBzettabyte
10008YByottabyte
10009RBronnabyte
100010QBquettabyte
Binary
ValueIECMemory
1024KiBkibibyteKBkilobyte
10242MiBmebibyteMBmegabyte
10243GiBgibibyteGBgigabyte
10244TiBtebibyteTBterabyte
10245PiBpebibyte
10246EiBexbibyte
10247ZiBzebibyte
10248YiByobibyte
10249RiBrobibyte
102410QiBquebibyte
Orders of magnitude of data

Thekilobyte is a multiple of the unitbyte fordigital information.

TheInternational System of Units (SI) defines the prefixkilo as a multiplication factor of 1000 (103); therefore, one kilobyte is 1000 bytes.[1] The internationally recommended unit symbol for the kilobyte iskB.[1]

In some areas ofinformation technology, particularly in reference torandom-access memory capacity,kilobyte instead often refers to 1024 (210) bytes. This arises from the prevalence of sizes that arepowers of two in modern digital memory architectures, coupled with the coincidence that 210 differs from 103 by less than 2.5%.

Thekibibyte is defined as 1024 bytes, avoiding the ambiguity issues of thekilobyte.[1]

Definitions and usage

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Decimal (1000 bytes)

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In theInternational System of Units (SI) themetric prefixkilo means 1,000 (103); therefore, one kilobyte is 1000 bytes. The unit symbol is kB.

This is the definition standardised by theInternational Electrotechnical Commission (IEC).[2] This definition, and the related definitions of the prefixesmega (1,000,000),giga (1,000,000,000), etc., are most commonly used fordata transfer rates incomputer networks, internal bus, hard drive and flash media transfer speeds, and for the capacities of moststorage media, particularlyhard disk drives,[3]flash-based storage,[4] andDVDs. It is also consistent with the other uses of the metric prefixes in computing, such asCPU clock speeds ormeasures of performance.

The international standardIEC 80000-13 uses the term "byte" to mean eightbits (1 B = 8 bit). Therefore, 1 kB = 8000 bit. One thousand kilobytes (1000 kB) is equal to onemegabyte (1 MB), where 1 MB is one million bytes.

Binary (1024 bytes)

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The term 'kilobyte' has traditionally been used to refer to 1024 bytes (210 B).[5][6][7] The usage of the metric prefixkilo for binary multiples arose as a convenience, because 1024 is approximately 1000.[8]

The binary interpretation of metric prefixes is still prominently used by theMicrosoft Windows operating system.[9] Binary interpretation is also used forrandom-access memory capacity, such as main memory andCPU cache size, due to the prevalentbinary addressing of memory.

The binary meaning of the kilobyte for 1024 bytes typically uses the symbol KB, with an uppercase letterK. TheB is sometimes omitted in informal use. For example, a processor with 65,536 bytes of cache memory might be said to have "64 K" of cache. In this convention, one thousand and twenty-four kilobytes (1024 KB) is equal to one megabyte (1 MB), where 1 MB is 10242 bytes.

In December 1998, theIEC addressed such multiple usages and definitions by creating prefixes such as kibi, mebi, gibi, etc., to unambiguously denote powers of 1024.[10] Thus the kibibyte, symbol KiB, represents 210 bytes = 1024 bytes. These prefixes are now part of IEC 80000-13. The IEC further specified that the kilobyte should only be used to refer to 1000 bytes. TheInternational System of Units restricts the use of the SI prefixes strictly to powers of 10.[11]

Use of term

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  • TheShugart SA-400 514-inchfloppy disk (1976) held 109,375 bytes unformatted,[12] and was advertised as "110 Kbyte", using the 1000 convention.[13] Likewise, the 8-inchDEC RX01 floppy (1975) held 256,256 bytes formatted, and was advertised as "256k".[14] On the other hand, theTandon 514-inchDD floppy format (1978) held 368,640 (which is 360×1024) bytes, but was advertised as "360 KB", following the 1024 convention.
  • Early home computer systems would often advertise using the 1024 convention, hence the naming of theCommodore 64,Commodore 128, and theAmstrad CPC 464.
  • On modern systems, all versions ofMicrosoft Windows divide by 1024 and represent a 65,536-byte file as "64 KB".[9] Conversely,Mac OS X Snow Leopard and newer represent this as 66 kB, rounding to the nearest 1000 bytes;[15] file sizes are reported with decimal prefixes.[16]
  • As of 2016,[update] the binary interpretation was still used in marketing and billing by some telecommunication companies, such asVodafone,[17]AT&T,[18]Orange[19] andTelstra.[20]

Data examples

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See also

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References

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  1. ^abcInternational StandardIEC 80000-13 Quantities and Units – Part 13: Information science and technology, International Electrotechnical Commission (2008).
  2. ^Prefixes for Binary MultiplesArchived 2007-08-08 at theWayback Machine — The NIST Reference on Constants, Units, and Uncertainty
  3. ^1977 Disk/Trend Report Rigid Disk Drives, published June 1977
  4. ^SanDisk USB Flash DriveArchived 2008-05-13 at theWayback Machine "Note: 1 megabyte (MB) = 1 million bytes; 1 gigabyte (GB) = 1 billion bytes."
  5. ^Kilobyte – Definition and More from the Free Merriam-Webster DictionaryArchived 2010-04-09 at theWayback Machine. Merriam-webster.com (2010-08-13). Retrieved on 2011-01-07.
  6. ^Kilobyte | Define Kilobyte at Dictionary.comArchived 2010-09-01 at theWayback Machine. Dictionary.reference.com (1995-09-29). Retrieved on 2011-01-07.
  7. ^Definition of kilobyte from Oxford Dictionaries OnlineArchived 2006-06-25 at theWayback Machine. Askoxford.com. Retrieved on 2011-01-07.
  8. ^"Prefixes for binary multiples".iec.ch. International Electrotechnical Commission.Archived from the original on 25 September 2016. Retrieved1 October 2016.
  9. ^ab"Determining Actual Disk Size: Why 1.44 MB Should Be 1.40 MB". Support.microsoft.com. 2003-05-06.Archived from the original on 2014-02-09. Retrieved2014-03-25.
  10. ^National Institute of Standards and Technology."Prefixes for binary multiples".Archived from the original on 2007-08-08. "In December 1998 theInternational Electrotechnical Commission (IEC) [...] approved as an IEC International Standard names and symbols for prefixes for binary multiples for use in the fields of data processing and data transmission."
  11. ^The International System of Units(PDF) (9th ed.), International Bureau of Weights and Measures, Dec 2022, p. 143,ISBN 978-92-822-2272-0. "The SI prefixes refer strictly to powers of 10. They should not be used to indicate powers of 2 (for example, one kilobit represents 1000 bits and not 1024 bits). The names and symbols for prefixes to be used with powers of 2 are recommended as follows: kibi Ki 210 [...]"
  12. ^"SA400 minifloppy". Swtpc.com. 2013-08-14. Archived fromthe original on 2014-05-27. Retrieved2014-03-25.
  13. ^"Shugart Associates SA 400 minifloppy TM Disk Drive"(PDF). Archived fromthe original(PDF) on 2011-06-08. Retrieved2011-06-24.
  14. ^"RXS/RX11 floppy disk system maintenance manual"(PDF). Archived fromthe original(PDF) on 2011-04-23. Retrieved2011-06-24.
  15. ^"How OS X and iOS report storage capacity". Support.apple.com. 2013-07-01.Archived from the original on 2014-03-04. Retrieved2014-03-25.
  16. ^"How Mac OS X reports drive capacity". Apple Inc. 2009-08-27.Archived from the original on 2009-12-22. Retrieved2009-10-16.
  17. ^"3G/GPRS data rates". Vodafone Ireland.Archived from the original on 26 October 2016. Retrieved26 October 2016.
  18. ^"Data Measurement Scale". AT&T. Retrieved26 October 2016.[permanent dead link]
  19. ^"Internet Mobile Access". Orange Romania. Archived fromthe original on 26 October 2016. Retrieved26 October 2016.
  20. ^"Our Customer Terms"(PDF). Telstra. p. 7.Archived(PDF) from the original on 10 April 2017. Retrieved26 October 2016.
  21. ^"Vulgata Clementina".Archived from the original on 2022-12-05. Retrieved2024-02-29.pater noster qui es in cælis sanctificetur nomen tuum adveniat regnum tuum fiat voluntas tua sicut in cælo et in terra panem nostrum supersubstantialem da nobis hodie et dimitte nobis debita nostra sicut et nos dimittimus debitoribus nostris et ne nos inducas in tentationem sed libera nos a malo
  22. ^Poe, Edgar Allan."The Cask of Amontillado".Archived from the original on 2024-05-08. Retrieved2024-02-29 – via Project Gutenberg.
  23. ^Dickens, Charles (July 1, 1998).Great Expectations.Archived from the original on February 29, 2024. RetrievedFebruary 29, 2024 – via Project Gutenberg.
  24. ^Melville, Herman (July 1, 2001).Moby Dick; Or, The Whale.Archived from the original on February 29, 2024. RetrievedFebruary 29, 2024 – via Project Gutenberg.
Platform-independent units
Platform-dependent units
Metric bit units
Metric byte units
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