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The '''kilobyte''' for 1000 [[bytes]] (symbol: '''kB''') or '''Kilobyte''' ('''[[kibibyte]]''') for 1024 bytes (symbol: '''KB''' or '''KiB''' or informally '''KBytes''') are two definitions for multiples of the unit byte for [[Computer data storage|digital information]]. Although the [[International System of Units|SI-prefix]] ''[[kilo-]]'' means 1000, the term ''kilobyte'' and the symbol ''KB'' have usually been used to refer to 1024 (2<sup>10</sup>) bytes, in the fields of [[computer science]] and [[information technology]]<ref>[http://www.merriam-webster.com/dictionary/kilobyte Kilobyte – Definition and More from the Free Merriam-Webster Dictionary] Merriam-webster.com (2010-08-13). Retrieved on 2011-01-07.</ref><ref>[http://dictionary.reference.com/browse/kilobyte Kilobyte | Define Kilobyte at Dictionary.com]. Dictionary.reference.com (1995-09-29). Retrieved on 2011-01-07.</ref><ref>[http://www.askoxford.com/concise_oed/kilobyte?view=uk definition of kilobyte from Oxford Dictionaries Online]. Askoxford.com. Retrieved on 2011-01-07.</ref> except when where referring to data transfer rates and to disk storage space.{{cn|date=December 2013}} The symbol ''kB'' correctly however refers to 1000 (10<sup>3</sup>) bytes as used in modern times for file sizes. [[CPU cache]]s always use [[binary prefix]]es, where ''kB'' is never appropriate, as does [[random-access memory]] capacity (not file sizes or flash-based storage) according to [[JEDEC memory standards|JEDEC-standard]] for memory modules. Informally sometimes the ''B'' is dropped, then ''K'' (the SI symbol for ''[[kelvin]]'' not ''kilo-''), given the right context, can been understood as 1024 bytes and ''k'' (always the lower case, SI prefix for 1000) can be taken for 1000 bytes. ''KB'' and ''kB'' are sometimes mistakenly used interchangeably, with or without the ''B'', not following any standard. The ''B'' should always be uppercase, because ''b'' means [[bit]]s, ''kb'' is [[kilobit]].
The '''kilobyte''' for 1000 [[bytes]] (symbol: '''kB''') or '''Kilobyte''' ('''[[kibibyte]]''') for 1024 bytes (symbol: '''KB''' or '''KiB''' or informally '''KBytes''') are two definitions for multiples of the unit byte for [[Computer data storage|digital information]]. Although the [[International System of Units|SI-prefix]] ''[[kilo-]]'' means 1000, the term ''kilobyte'' and the symbol ''KB'' have usually been used to refer to 1024 (2<sup>10</sup>) bytes, in the fields of [[computer science]] and [[information technology]]<ref>[http://www.merriam-webster.com/dictionary/kilobyte Kilobyte – Definition and More from the Free Merriam-Webster Dictionary] Merriam-webster.com (2010-08-13). Retrieved on 2011-01-07.</ref><ref>[http://dictionary.reference.com/browse/kilobyte Kilobyte | Define Kilobyte at Dictionary.com]. Dictionary.reference.com (1995-09-29). Retrieved on 2011-01-07.</ref><ref>[http://www.askoxford.com/concise_oed/kilobyte?view=uk definition of kilobyte from Oxford Dictionaries Online]. Askoxford.com. Retrieved on 2011-01-07.</ref> except when where referring to data transfer rates {{cn}} and to disk storage space.<ref>1977 Disk/Trend Report – Rigid Disk Drives, published June 1977</ref> The symbol ''kB'' correctly however refers to 1000 (10<sup>3</sup>) bytes as used in modern times for file sizes. [[CPU cache]]s always use [[binary prefix]]es, where ''kB'' is never appropriate, as does [[random-access memory]] capacity (not file sizes or flash-based storage) according to [[JEDEC memory standards|JEDEC-standard]] for memory modules. Informally sometimes the ''B'' is dropped, then ''K'' (the SI symbol for ''[[kelvin]]'' not ''kilo-''), given the right context, can been understood as 1024 bytes and ''k'' (always the lower case, SI prefix for 1000) can be taken for 1000 bytes. ''KB'' and ''kB'' are sometimes mistakenly used interchangeably, with or without the ''B'', not following any standard. The ''B'' should always be uppercase, because ''b'' means [[bit]]s, ''kb'' is [[kilobit]].


==Definitions==
==Definitions==

Revision as of 21:20, 1 December 2013

Multiple-byte units
Decimal
Value Metric
1000 kB kilobyte
10002 MB megabyte
10003 GB gigabyte
10004 TB terabyte
10005 PB petabyte
10006 EB exabyte
10007 ZB zettabyte
10008 YB yottabyte
10009 RB ronnabyte
100010 QB quettabyte
Binary
Value IEC Memory
1024 KiB kibibyte KB kilobyte
10242 MiB mebibyte MB megabyte
10243 GiB gibibyte GB gigabyte
10244 TiB tebibyte TB terabyte
10245 PiB pebibyte –
10246 EiB exbibyte –
10247 ZiB zebibyte –
10248 YiB yobibyte –
10249 – –
102410 – –
Orders of magnitude of data

The kilobyte for 1000 bytes (symbol: kB) or Kilobyte (kibibyte) for 1024 bytes (symbol: KB or KiB or informally KBytes) are two definitions for multiples of the unit byte for digital information. Although the SI-prefix kilo- means 1000, the term kilobyte and the symbol KB have usually been used to refer to 1024 (210) bytes, in the fields of computer science and information technology[1][2][3] except when where referring to data transfer rates [citation needed] and to disk storage space.[4] The symbol kB correctly however refers to 1000 (103) bytes as used in modern times for file sizes. CPU caches always use binary prefixes, where kB is never appropriate, as does random-access memory capacity (not file sizes or flash-based storage) according to JEDEC-standard for memory modules. Informally sometimes the B is dropped, then K (the SI symbol for kelvin not kilo-), given the right context, can been understood as 1024 bytes and k (always the lower case, SI prefix for 1000) can be taken for 1000 bytes. KB and kB are sometimes mistakenly used interchangeably, with or without the B, not following any standard. The B should always be uppercase, because b means bits, kb is kilobit.

Definitions

The unit kilobyte is commonly used to mean either 1000 or 1024 bytes. The 1024 number originated as compromise technical jargon for the byte multiples that needed to be expressed by the powers of 2 but lacked a convenient name. As 1024 (210) approximates 1000 (103), roughly corresponding SI multiples were used for binary multiples. In 1998 the International Electrotechnical Commission (IEC) proposed standards for binary prefixes, specifying the use of megabyte to strictly denote 10002 bytes and mebibyte to denote 10242 bytes. By the end of 2007, the IEC Standard had been adopted by the IEEE, EU, and NIST. Nevertheless, the term kilobyte continues to be widely used with the following two meanings:

Decimal

Binary

Examples

  • The HP 21MX real-time computer (1974) denoted 196,608 (which is 192×1024) as "196K",[9] while the HP 3000 business computer (1973) denoted 131,072 (which is 128×1024) as "128K".[10]
  • The Shugart SA-400 51⁄4-inch floppy disk (1976) held 109,375 bytes unformatted,[11] and was advertised as "110 Kbyte", using the 1000 convention.[12] Likewise, the 8-inch DEC RX01 floppy (1975) held 256,256 bytes formatted, and was advertised as "256k".[13] On the other hand, the Tandon 51⁄4-inch DD floppy format (1978) held 368,640 (which is 360×1024) bytes, but was advertised as "360 KB", following the 1024 convention.
  • On modern systems, Mac OS X Snow Leopard represents a 65,536 byte file as "66 KB",[14] rounding to the nearest 1000, while Microsoft Windows 7 would divide by 1024 and represent this as "64 KB".[15]

In December 1998, the IEC addressed such multiple usages and definitions by creating unique binary prefixes to denote multiples of 1024, such as “kibibyte (KiB)”, which represents 210, or 1024, bytes.[16]

See also

Notes

  1. ^ Kilobyte – Definition and More from the Free Merriam-Webster Dictionary Merriam-webster.com (2010-08-13). Retrieved on 2011-01-07.
  2. ^ Kilobyte | Define Kilobyte at Dictionary.com. Dictionary.reference.com (1995-09-29). Retrieved on 2011-01-07.
  3. ^ definition of kilobyte from Oxford Dictionaries Online. Askoxford.com. Retrieved on 2011-01-07.
  4. ^ 1977 Disk/Trend Report – Rigid Disk Drives, published June 1977
  5. ^ Prefixes for Binary Multiples — The NIST Reference on Constants, Units, and Uncertainty
  6. ^ SanDisk USB Flash Drive "Note: 1 megabyte (MB) = 1 million bytes; 1 gigabyte (GB) = 1 billion bytes."
  7. ^ "How Mac OS X reports drive capacity". Apple Inc. 2009-08-27. Retrieved 2009-10-16.
  8. ^ Sharma, Kapil; Mohammed J.; Norton, Peter C. Norton; Good, Nathan; Steidler-Dennison, Tony (2005). Professional Red Hat Enterprise Linux 3. John Wiley & Sons. p. 134. Disk manufacturers sell you their disks saying that a kilobyte is 1,000 bytes, that a megabyte is a thousand of those, and that a gigabyte is another thousand of those, giving you 1,000,000,000 bytes to a gigabyte when you buy a disk. The rest of the computer world, including the programmers who write Linux, thinks of a kilobyte as 1,024 bytes (2^10 bytes), a megabyte as 1,048,576 bytes (2^20), and a gigabyte as 1,073,741,824 bytes (2^30), which means that you're buying just a bit less than you might think.
  9. ^ Frankenberg, Robert (1974). "All Semiconductor Memory Selected for New Minicomputer Series" (PDF). Hewlett-Packard Journal. 26 (2). Hewlett-Packard: pg 15–20. Retrieved 2007-06-18. 196K-word memory size {{cite journal}}: |pages= has extra text (help); Unknown parameter |month= ignored (help)
  10. ^ Hewlett-Packard (November 1973). "HP 3000 Configuration Guide" (PDF). HP 3000 Computer System and Subsystem Data: pg 59. Retrieved 2010-01-22. {{cite journal}}: |pages= has extra text (help)
  11. ^ http://www.swtpc.com/mholley/SA400/SA400_Index.htm
  12. ^ http://www.swtpc.com/mholley/SA400/SA400_Datasheet.pdf
  13. ^ http://bitsavers.org/pdf/dec/disc/rx01/EK-RX01-MM-002_maint_Dec76.pdf
  14. ^ http://support.apple.com/kb/TS2419
  15. ^ http://support.microsoft.com/kb/121839
  16. ^ National Institute of Standards and Technology. "Prefixes for binary multiples". "In December 1998 the International 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."

References

"Terms, Definitions, and Letter Symbols for Microcomputers, Microprocessors, and Memory Integrated Circuits" (PDF). JEDEC Solid State Technology Association. December 2002. Retrieved 22 September 2013.

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