Gigabyte: Difference between revisions
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#REDIRECT [[Byte#Unit multiples]] |
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{{short description|Unit of information}} |
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{{About|a multiple of bytes|the binary unit of measurement|gibibyte|the company|Gigabyte Technology|other uses|Gigabyte (disambiguation)}} |
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{{Quantities of bytes}} |
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The '''gigabyte''' ({{IPAc-en|ˈ|ɡ|ɪ|ɡ|ə|b|aɪ|t|,_|ˈ|dʒ|ɪ|ɡ|ə|-}})<ref>The prefix ''giga'' may be pronounced two ways. [http://www.merriam-webster.com/dictionary/gigabyte Gigabyte - Definition and More from the Free Merriam-Webster Dictionary]</ref> is a multiple of the unit [[byte]] for digital information. The [[SI prefix|prefix]] ''[[giga-|giga]]'' means 10<sup>9</sup> in the [[International System of Units]] (SI). Therefore, one gigabyte is one billion bytes. The unit symbol for the gigabyte is '''GB'''. |
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This definition is used in all contexts of science, engineering, business, and many areas of computing, including hard drive, solid state drive, and tape capacities, as well as data transmission speeds. However, the term is also used in some fields of computer science and information technology to denote {{gaps|1|073|741|824}} (1024<sup>3</sup> or 2<sup>30</sup>) bytes, particularly for sizes of [[Random-access memory|RAM]]. The use of ''gigabyte'' may thus be ambiguous. Hard disk capacities as described and marketed by drive manufacturers using the standard metric definition of the gigabyte, but when a 400 GB drive's capacity is displayed by, for example, [[Microsoft Windows]], it is reported as 372 GB, using a binary interpretation. To address this ambiguity, the [[International System of Quantities]] standardizes the [[binary prefix]]es which denote a series of integer powers of 1024. With these prefixes, a memory module that is labeled as having the size "{{gaps|1|GB}}" has one [[gibibyte]] ({{gaps|1|GiB}}) of storage capacity. Using the ISQ definitions, the "372 GB" reported for the hard drive is actually 372 GiB (400 GB). |
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==Definition== |
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[[File:Laptop-hard-drive-exposed.jpg|thumb|right|This 2.5 inch [[Hard disk drive|hard drive]] can hold 500 GB (i.e., 500 billion bytes) of data.]] |
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The term ''gigabyte'' is commonly used to mean either 1000<sup>3</sup> bytes or 1024<sup>3</sup> bytes. The latter binary usage originated as compromise technical jargon for byte [[SI prefix|multiples]] that needed to be expressed in a power of 2, but lacked a convenient name. As 1024 (2<sup>10</sup>) is approximately 1000 (10<sup>3</sup>), roughly corresponding to SI multiples, it was used for binary multiples as well. |
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In 1998 the [[International Electrotechnical Commission]] (IEC) published standards for [[binary prefix]]es, requiring that the gigabyte strictly denote 1000<sup>3</sup> bytes and [[gibibyte]] denote 1024<sup>3</sup> bytes. By the end of 2007, the IEC Standard had been adopted by the [[IEEE]], [[European Union|EU]], and [[NIST]], and in 2009 it was incorporated in the [[IEC 80000-13|International System of Quantities]]. Nevertheless, the term gigabyte continues to be widely used with the following two different meanings: |
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===Base 10 (decimal)=== |
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* 1 GB = {{gaps|1|000|000|000}} bytes (= 1000<sup>3</sup> B = 10<sup>9</sup> B) |
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Based on powers of 10, this definition uses the prefix giga- as defined in the [[International System of Units]] (SI). This is the recommended definition by the [[International Electrotechnical Commission]] (IEC).<ref name="NIST">http://physics.nist.gov/cuu/Units/binary.html Prefixes for binary multiples</ref> This definition is used in [[computer network|networking]] contexts and most [[storage media]], particularly [[hard drive]]s, [[Flash memory|flash]]-based storage,<ref name="sandisk_gigabyte">[http://apac.sandisk.com/Products/Catalog(1349)-SanDisk_Extreme_Ducati_Edition_USB_Flash_Drive.aspx SanDisk USB Flash Drive] {{Webarchive|url=https://web.archive.org/web/20080513155718/http://apac.sandisk.com/Products/Catalog%281349%29-SanDisk_Extreme_Ducati_Edition_USB_Flash_Drive.aspx |date=13 May 2008 }} "Note: 1 megabyte (MB) = 1 million bytes; 1 gigabyte (GB) = 1 billion bytes."</ref><ref name="kingston_gigabyte">[http://www.kingston.com/us/usb/storage_chart Storage Chart] "Megabyte (MB) = 1,000,000 bytes; 1 Gigabyte (GB) = 1,000,000,000 bytes; 1TB = 1,000,000,000,000 bytes"</ref><ref>[http://osubeaverstore.com/Product/Detail/ipad-pro-11-wi-fi-512gb-assorted-colors/]</ref> and [[DVD]]s, and is also consistent with the other uses of the [[SI prefix]] in computing, such as [[Megahertz#Megahertz in computing|CPU clock speeds]] or [[FLOPS|measures of performance]]. The file manager of [[Mac OS X]] version 10.6 and later versions are a notable example of this usage in software, which report files sizes in decimal units.<ref name="Apple Inc">{{cite web|url=http://support.apple.com/kb/TS2419 |title=How Mac OS X reports drive capacity |publisher=Apple Inc |date=2009-08-27 |accessdate=2009-10-16}}</ref> |
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===Base 2 (binary)=== |
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* 1 GiB = {{gaps|1|073|741|824}} bytes (= 1024<sup>3</sup> B = 2<sup>30</sup> B). |
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The binary definition uses powers of the base 2, as does the architectural principle of [[Binary code|binary]] [[computer]]s. |
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This usage is widely promulgated by some [[operating system]]s, such as [[Microsoft Windows]] in reference to [[computer memory]] (e.g., [[Random-access memory|RAM]]). This definition is synonymous with the unambiguous unit [[gibibyte]]. |
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==Consumer confusion== |
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Since the first disk drive, the [[IBM 350]], disk drive manufacturers expressed [[hard drive]] capacities using decimal prefixes. With the advent of gigabyte-range drive capacities, manufacturers based most consumer [[hard drive]] capacities in certain size classes expressed in decimal gigabytes, such as "500 GB". The exact capacity of a given drive model is usually slightly larger than the class designation. Practically all manufacturers of hard disk drives and flash-memory disk devices<ref name="sandisk_gigabyte"/><ref name="kingston_gigabyte"/> continue to define one gigabyte as {{gaps|1|000|000|000|bytes}}, which is displayed on the packaging. Some operating systems such as OS X<ref>{{Cite web|url=https://support.apple.com/en-us/HT201402|title=How OS X and iOS report storage capacity - Apple Support|website=support.apple.com|access-date=2016-06-29}}</ref> express hard drive capacity or file size using decimal multipliers, while others such as [[Microsoft Windows]] report size using binary multipliers. This discrepancy causes confusion, as a disk with an advertised capacity of, for example, {{nowrap|400 GB}} (meaning {{gaps|400|000|000|000|bytes}}) might be reported by the operating system as {{nowrap|372 GB}}, meaning 372 GiB. |
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The [[JEDEC memory standards]] use '''IEEE 100''' nomenclature which quote the gigabyte as {{gaps|1|073|741|824|bytes}} (2<sup>30</sup> bytes).<ref>{{Cite journal |
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| last = JEDEC Solid State Technology Association |
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| title = Terms, Definitions, and Letter Symbols for Microcomputers, Microprocessors, and Memory Integrated Circuits |
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| journal = Jesd 100B.01 |
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| date = December 2002 |
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| url = http://www.jedec.org/download/search/JESD100B01.pdf |
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| postscript = <!--None--> |
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}}</ref> |
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The difference between units based on decimal and binary prefixes increases as a [[Semilog|semi-logarithmic]] (linear-log) function—for example, the decimal kilobyte value is nearly 98% of the kibibyte, a [[megabyte]] is under 96% of a mebibyte, and a gigabyte is just over 93% of a gibibyte value. This means that a 300 GB (279 GiB) hard disk might be indicated variously as 300 GB, 279 GB or 279 GiB, depending on the operating system. As storage sizes increase and larger units are used, these differences become even more pronounced. |
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===US lawsuits=== |
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The most recent lawsuits arising from alleged consumer confusion over the binary and decimal definitions used for "gigabyte" have ended in favor of the manufacturers, with courts holding that the legal definition of gigabyte or GB is 1 GB = 1,000,000,000 (10^9) bytes (the decimal definition) rather than the binary definition (2^30) for commercial transactions. Specifically, the courts held that "the U.S. Congress has deemed the decimal definition of gigabyte to be the 'preferred' one for the purposes of 'U.S. trade and commerce' .... The California Legislature has likewise adopted the decimal system for all 'transactions in this state.'”<ref name="Order Granting Motion to Dismiss">{{cite web |
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| url = https://www.courthousenews.com/wp-content/uploads/2020/01/flashdrives.pdf |
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| title = Order Granting Motion to Dismiss |
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| publisher = [[United States District Court]] |
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| accessdate = 2020-01-24 |
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}}</ref> |
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Earlier lawsuits had ended in settlement with no court ruling on the question, such as a lawsuit against drive manufacturer [[Western Digital]].<ref name="WesternDigital">{{cite web |
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| last = Mook |
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| first = Nate |
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| date = 2006-06-28 |
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| url = http://www.betanews.com/article/Western-Digital-Settles-Capacity-Suit/1151510648 |
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| title = Western Digital Settles Capacity Suit |
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| publisher = betanews |
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| accessdate = 2009-03-30 |
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}}</ref><ref name="Baskin-2006-02-01">{{cite web |
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| last = Baskin |
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| first = Scott D. |
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| date = 2006-02-01 |
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| url = http://www.wdc.com/settlement/docs/document20.htm |
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| title = Defendant Western Digital Corporation's Brief in Support of Plaintiff's Motion for Preliminary Approval |
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| work = Orin Safier v. Western Digital Corporation |
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| publisher = [[Western Digital Corporation]] |
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| accessdate = 2009-03-30 |
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}}</ref> Western Digital settled the challenge and added explicit disclaimers to products that the usable capacity may differ from the advertised capacity.<ref name="WesternDigital"/> |
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Seagate was sued on similar grounds and also settled.<ref name="WesternDigital"/><ref name="Seagate">{{cite news |
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| last = Judge |
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| first = Peter |
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| date = 2007-10-26 |
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| url = http://www.zdnet.com/seagate-pays-out-over-gigabyte-definition-3039290393/ |
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| title = Seagate pays out over gigabyte definition |
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| work = ZDNet |
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| accessdate = 2014-09-16 |
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}}</ref> |
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===Other contexts=== |
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Because of their physical design, the capacity of modern computer random access memory devices, such as [[DIMM]] modules, is always a multiple of a power of 1024. It is thus convenient to use prefixes denoting powers of 1024, known as [[binary prefixes]], in describing them. For example, a memory capacity of {{gaps|1|073|741|824|bytes}} is conveniently expressed as 1 [[gibibyte|GiB]] rather than as 1.074 GB. The former specification is, however, often quoted as "1 GB" when applied to random access memory.<ref name=TS-GiB>{{cite web|last1=Percival|first1=Colin|title=Why is 1 GB equal to 10^9 bytes instead of 2^30?|url=http://www.tarsnap.com/GB-why.html|publisher=tarsnap.com|accessdate=1 November 2015}}</ref> |
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Software allocates memory in varying degrees of granularity as needed to fulfill data structure requirements and binary multiples are usually not required. Other computer capacities and rates, like [[Computer storage|storage]] hardware size, [[data transfer]] rates, [[clock speed]]s, [[FLOPS|operations per second]], etc., do not depend on an inherent [[base (exponentiation)|base]], and are usually presented in decimal units. For example, the manufacturer of a "300 GB" hard drive is claiming a capacity of {{gaps|300|000|000|000|bytes}}, not 300x1024<sup>3</sup> (which would be {{gaps|322|122|547|200}}) bytes. |
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==Examples of gigabyte-sized storage== |
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<!-- Only include examples of approximately 1 GB, and only cases where the example is actually available, not announcements of future uses --> |
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* One hour of [[Standard-definition television|SDTV]] video at 2.2 [[Mbit]]/s is approximately 1 GB. |
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* Seven minutes of [[High-definition television|HDTV]] video at 19.39 Mbit/s is approximately 1 GB. |
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* 114 minutes of uncompressed [[Compact Disc|CD-quality]] audio at 1.4 Mbit/s is approximately 1 GB. |
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* A single layer [[DVD+R]] disc can hold about 4.7 GB. |
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* A dual-layered [[DVD+R]] disc can hold about 8.5 GB. |
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* A single layer [[Blu-ray]] can hold about 25 GB. |
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* A dual-layered [[Blu-ray]] can hold about 50 GB. |
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== Unicode character == |
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The "gigabyte" symbol is encoded by [[Unicode]] at code point {{unichar|3387|Square GB}} ❰ {{resize|150%|㎇}} ❱.<ref name="Unicode-U3300">{{cite web |url=https://www.unicode.org/charts/PDF/U3300.pdf |access-date=24 May 2019 |title=The Unicode Standard 12.0 – CJK Compatibility ❰ Range: 3300—33FF ❱ |author=Unicode Consortium |author-link=Unicode Consortium |date=2019 |website=Unicode.org}}</ref> |
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==See also== |
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* [[Orders of magnitude (data)]] |
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* [[Binary prefix]] |
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==References== |
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{{Reflist}} |
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==External links== |
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* http://physics.nist.gov/cuu/Units/binary.html |
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* http://www.quinion.com/words/turnsofphrase/tp-kib1.htm |
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* https://www.nist.gov/public_affairs/techbeat/tb9903.htm |
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{{Computer Storage Volumes}} |
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{{Use dmy dates|date=June 2019}} |
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[[Category:Units of information]] |
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Revision as of 02:21, 11 December 2020
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