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Kilobyte

Multiples of bytes
SI decimal prefixesBinary
usage
IEC binary prefixes
Name
(Symbol)
ValueName
(Symbol)
Value
kilobyte (kB)103210kibibyte (KiB)210
megabyte (MB)106220mebibyte (MiB)220
gigabyte (GB)109230gibibyte (GiB)230
terabyte (TB)1012240tebibyte (TiB)240
petabyte (PB)1015250pebibyte (PiB)250
exabyte (EB)1018260exbibyte (EiB)260
zettabyte (ZB)1021270zebibyte (ZiB)270
yottabyte (YB)1024280yobibyte (YiB)280
See also: Multiples of bits · Orders of magnitude of data

The kilobyte (symbol: kB) is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol kB have historically been used to refer to either 1024 (210) bytes or 1000 (103) bytes, dependent upon context, in the fields of computer science and information technology.[1][2][3]

For example:

  • The HP 21MX real-time computer (1974) denoted 196,608 (which is 192�-1024) as "196K",[4] while the HP 3000 business computer (1973) denoted 131,072 (which is 128�-1024) as "128K".[5]
  • The Shugart SA-400 514-inch floppy disk (1976) held 109,375 bytes unformatted,[6] and was advertised as "110 Kbyte", using the 1000 convention.[7] Likewise, the 8-inch DEC RX01 floppy (1975) held 256,256 bytes formatted, and was advertised as "256k".[8] On the other hand, the Tandon 514-inch DD floppy format (1978) held 368,640 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",[9] rounding to the nearest 1000, while Microsoft Windows 7 would divide by 1024 and represent this as "64 KB".[10]

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.[11] However, adoption by the computer industry has not been universal, particularly when communicating in a public context, such as to consumers of computer or computer based products.[12][13][14][15]

Examples of use

  • 1 kilobyte: very short story
  • 2 kilobytes: typewritten page
  • 10 kilobytes: page from an encyclopedia[16]

See also

References

  1. ^ definition of kilobyte from Oxford Dictionaries Online. Askoxford.com. Retrieved on 2011-01-07.
  2. ^ Kilobyte – Definition and More from the Free Merriam-Webster Dictionary. Merriam-webster.com (2010-08-13). Retrieved on 2011-01-07.
  3. ^ Kilobyte | Define Kilobyte at Dictionary.com. Dictionary.reference.com (1995-09-29). Retrieved on 2011-01-07.
  4. ^ Frankenberg, Robert (October 1974). "All Semiconductor Memory Selected for New Minicomputer Series" (PDF). Hewlett-Packard Journal (Hewlett-Packard) 26 (2): pg 15–20. http://www.hpl.hp.com/hpjournal/pdfs/ IssuePDFs/1974-10.pdf. Retrieved 2007-06-18. "196K-word memory size"
  5. ^ Hewlett-Packard (November 1973). "HP 3000 Configuration Guide" (PDF). HP 3000 Computer System and Subsystem Data: pg 59. http://www.bitsavers.org/pdf/hp/3000/ hp3000/5952-4500_optionsBrochure_Nov7 3.pdf. Retrieved 2010-01-22.
  6. ^ http://www.swtpc.com/mholley/SA400/SA 400_Index.htm
  7. ^ http://www.swtpc.com/mholley/SA400/SA 400_Datasheet.pdf
  8. ^ http://bitsavers.org/pdf/dec/disc/rx0 1/EK-RX01-MM-002_maint_Dec76.pdf
  9. ^ http://support.apple.com/kb/TS2419
  10. ^ http://support.microsoft.com/kb/12183 9
  11. ^ National Institute of Standards and Technology. "Prefixes for binary multiples". http://physics.nist.gov/cuu/Units/bin ary.html. "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."
  12. ^ Upgrading and Repairing PCs, Scott Mueller, Pg. 596, ISBN 0-7897-2974-1
  13. ^ The silicon web: physics for the Internet age, Michael G. Raymer, Pg. 40, ISBN 978-1-4398-0311-0
  14. ^ Knuth: Recent News. Cs-staff.stanford.edu. Retrieved on 2011-01-07.
  15. ^ Atwood, Jeff. (2007-09-10) Gigabyte: Decimal vs. Binary. Coding Horror. Retrieved on 2011-01-07.
  16. ^ Huggins, James. "How Much Data Is That?". jamesshuggins. http://www.jamesshuggins.com/h/tek1/h ow_big.htm. Retrieved 27 September 2011.
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