Kibibyte

The kibibyte is a multiple of the unit byte for digital information.[1] The binary prefix kibi means 210, or 1024; therefore, 1 kibibyte is 1024 bytes. The unit symbol for the kibibyte is KiB.

Multiples of bytes
Decimal
Value Metric
1 Bbyte
1000 kBkilobyte
10002 MBmegabyte
10003 GBgigabyte
10004 TBterabyte
10005 PBpetabyte
10006 EBexabyte
10007 ZBzettabyte
10008 YByottabyte
Binary
Value IEC JEDEC
1 Bbyte Bbyte
1024 KiBkibibyte KBkilobyte
10242 MiBmebibyte MBmegabyte
10243 GiBgibibyte GBgigabyte
10244 TiBtebibyte –
10245 PiBpebibyte –
10246 EiBexbibyte –
10247 ZiBzebibyte –
10248 YiByobibyte –
Orders of magnitude of data

The unit was established by the International Electrotechnical Commission (IEC) in 1998,[2] has been accepted for use by all major standards organizations, and is part of the International System of Quantities.[3] The kibibyte was designed to replace the kilobyte in those computer science contexts in which the term kilobyte is used to mean 1024 bytes. The interpretation of kilobyte to denote 1024 bytes, conflicting with the SI definition of the prefix kilo (1000), used to be common.[4]

Definition

The unit prefix kibi specifies multiplication by 210 (1024). It was derived as a portmanteau from the words kilo and binary, indicating its origin in the closeness in value to the SI prefix kilo (1000). While the SI prefix is written with lowercase (k), all IEC binary prefixes start with an uppercase letter.[5]

Therefore, the definition of the kibibyte is:

1 kibibyte (KiB) = 210 bytes = 1024 bytes.

The next larger unit of information in the sequence with IEC binary prefixes is the mebibyte (MiB) (220 bytes):

1024 kibibytes = 1 mebibyte.

IEC specification 80000-13 defines one byte as 8 bits (1 B = 8 bit). Therefore,

1 kibibyte = 8192 bits.

History

The kibibyte is closely related to the kilobyte, which equals 1000 bytes, as the prefix kilo is defined in the International System of Units. The kibibyte was established by the International Electrotechnical Commission (IEC) in 1998,[2]

Prior to the definition of the binary prefixes, the kilobyte generally represented 1024 bytes in most fields of computer science, but was sometimes used to mean exactly one thousand bytes. When describing random access memory, it typically meant 1024 bytes, but when describing disk drive storage, it meant 1000bytes.[6] The errors associated with this ambiguity are relatively small (2.4%).

In 1995, the International Union of Pure and Applied Chemistry's Interdivisional Committee on Nomenclature and Symbols attempted to resolve this ambiguity by proposing a set of binary prefixes for the powers of 1024.[7][8] After adopting the proposal, the IEC published the standard in January 1999.[9][10]

In 1999, Donald Knuth suggested to call the kibibyte a "large kilobyte" (KKB).[11]

In spite of the formal adoption of the kibibyte, kilobyte continued to be used often to mean 1024 bytes as late as 2007 in some product advertising and other contexts.[12][13][14]

gollark: And, er, zombies.
gollark: Oh, and trees which hover if you remove the bottom block.
gollark: It's *basically* as realistic as magic boxes which turn ores into conveniently pure cuboids.
gollark: Because *tanks can drive anyway*, and Psi can't make them go *that* fast.
gollark: No, it's not.

See also

References
  1. International Electrotechnical Commission (2007). "Prefixes for binary multiples". Retrieved 2014-01-09.
  2. International Electrotechnical Commission (January 1999), IEC 60027-2 Amendment 2: Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics
  3. "IEC 80000-13:2008". International Organization for Standardization. Retrieved 2013-07-21.
  4. "Definitions of the SI units: The binary prefixes". physics.nist.gov. Retrieved 2018-04-09.
  5. National Institute of Standards and Technology. "Prefixes for binary multiples". Retrieved 2015-10-09.
  6. NIST "Prefixes for binary multiples" https://physics.nist.gov/cuu/Units/binary.html
  7. IUCr 1995 Report - IUPAC Interdivisional Committee on Nomenclature and Symbols (IDCNS) http://ww1.iucr.org/iucr-top/cexec/rep95/idcns.htm
  8. "Binary Prefix" University of Auckland Department of Computer Science https://wiki.cs.auckland.ac.nz/stageonewiki/index.php/Binary_prefix
  9. NIST "Prefixes for binary multiples" https://physics.nist.gov/cuu/Units/binary.html
  10. Amendment 2 to IEC International Standard IEC 60027-2: Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics.
  11. "What is a kilobyte?". Retrieved 2010-05-20.
  12. "Safier vs WDC complaint". WesternDigital.com. Archived from the original on October 16, 2007. Retrieved 2007-11-15.
  13. Grainger, Brian (7 August 2005). "I've got a bigger gigabyte than you!". Independent Computer Products Users Group (ICPUG). Retrieved 2007-11-15.
  14. Barry Wittman; Aditya Mathur; Tim Korb (30 December 2012). Start Concurrent: An Introduction to Problem Solving in Java with a Focus on Concurrency, 2013 Edition. Purdue University Press. p. 5. ISBN 978-1-55753-672-3. Retrieved 1 May 2013.
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