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 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.^[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 5¹⁄₄-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 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",^[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[link]

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

See also[link]

• Data rate units
• Timeline of binary prefixes
• History of the floppy disk

References[link]

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_Nov73.pdf. Retrieved 2010-01-22. 
6. ^ http://www.swtpc.com/mholley/SA400/SA400_Index.htm
7. ^ http://www.swtpc.com/mholley/SA400/SA400_Datasheet.pdf
8. ^ http://bitsavers.org/pdf/dec/disc/rx01/EK-RX01-MM-002_maint_Dec76.pdf
9. ^ http://support.apple.com/kb/TS2419
10. ^ http://support.microsoft.com/kb/121839
11. ^ 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."
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/how_big.htm. Retrieved 27 September 2011.