Kilobyte

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Multiples of bytes
SI decimal prefixes Binary
usage		 IEC binary prefixes
Name
(Symbol)		 Value Name
(Symbol)		 Value
kilobyte (kB/KB) 103 210 kibibyte (KiB) 210
megabyte (MB) 106 220 mebibyte (MiB) 220
gigabyte (GB) 109 230 gibibyte (GiB) 230
terabyte (TB) 1012 240 tebibyte (TiB) 240
petabyte (PB) 1015 250 pebibyte (PiB) 250
exabyte (EB) 1018 260 exbibyte (EiB) 260
zettabyte (ZB) 1021 270 zebibyte (ZiB) 270
yottabyte (YB) 1024 280 yobibyte (YiB) 280
See also: Multiples of bits · Orders of magnitude of data

The kilobyte (symbol: kB)[1] is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol kB or 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.[2][3][4]

For example:

  • The HP 21MX real-time computer (1974) denoted 196,608 (which is 192×1024) as "196K",[5] while the HP 3000 business computer (1973) denoted 131,072 (which is 128×1024) as "128K".[6]
  • The Shugart SA-400 51⁄4-inch floppy disk (1976) held 109,375 bytes unformatted,[7] and was advertised as "110 Kbyte", using the 1000 convention.[8] Likewise, the 8-inch DEC RX01 floppy (1975) held 256,256 bytes formatted, and was advertised as "256k".[9] On the other hand, the Tandon 51⁄4-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",[10] rounding to the nearest 1000, while Microsoft Windows 7 would divide by 1024 and represent this as "64 KB".[11]

In December 1998, the IEC addressed these dual definitions of the conventional prefixes by creating unique binary prefixes and prefix symbols to denote multiples of 1024, such as “kibibyte (KiB)”, which exclusively denotes 210 or 1024 bytes.[12] With consistent adoption, this would liberate the standard unit prefixes to unambiguously refer only to their strict decimal definitions, wherein kilobyte would be understood to represent only 1000 bytes. However, adoption by the computer industry has been slow, leaving the exact meaning of a unit ambiguous.[13][14][15][16]

[edit] Examples of use

  • 1 kilobyte: (very) short story
  • 2 kilobytes: typewritten page
  • 10 kilobytes: page out of an encyclopedia[17]

[edit] See also

[edit] References

  1. ^ Note that lowercase "k" is the proper unit symbol for the prefix kilo. Uppercase “K” is properly the unit symbol for the unit of thermodynamic temperature kelvin. Nonetheless, it is exceedingly common within the computing industry when denoting binary capacity—particularly in marketing literature and product packaging—to use uppercase K and no space (1KB), although “1 KB” is not incorrect and is often considered more suitable in technical writing.
  2. ^ definition of kilobyte from Oxford Dictionaries Online. Askoxford.com. Retrieved on 2011-01-07.
  3. ^ Kilobyte – Definition and More from the Free Merriam-Webster Dictionary. Merriam-webster.com (2010-08-13). Retrieved on 2011-01-07.
  4. ^ Kilobyte | Define Kilobyte at Dictionary.com. Dictionary.reference.com (1995-09-29). Retrieved on 2011-01-07.
  5. ^ 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" 
  6. ^ 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_Nov73.pdf. Retrieved 2010-01-22. 
  7. ^ http://www.swtpc.com/mholley/SA400/SA400_Index.htm
  8. ^ http://www.swtpc.com/mholley/SA400/SA400_Datasheet.pdf
  9. ^ http://bitsavers.org/pdf/dec/disc/rx01/EK-RX01-MM-002_maint_Dec76.pdf
  10. ^ http://support.apple.com/kb/TS2419
  11. ^ http://support.microsoft.com/kb/121839
  12. ^ National Institute of Standards and Technology. "Prefixes for binary multiples". http://physics.nist.gov/cuu/Units/binary.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."
  13. ^ Upgrading and Repairing PCs, Scott Mueller, Pg. 596, ISBN 0789729741
  14. ^ The silicon web: physics for the Internet age, Michael G. Raymer, Pg. 40, ISBN 9781439803110
  15. ^ Knuth: Recent News. Cs-staff.stanford.edu. Retrieved on 2011-01-07.
  16. ^ Atwood, Jeff. (2007-09-10) Gigabyte: Decimal vs. Binary. Coding Horror. Retrieved on 2011-01-07.
  17. ^ Huggins, James. "How Much Data Is That?". jamesshuggins. http://www.jamesshuggins.com/h/tek1/how_big.htm. Retrieved 27 September 2011. 
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