Kilobyte

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Multiples of bytes
Decimal
ValueMetric
1000kBkilobyte
10002MBmegabyte
10003GBgigabyte
10004TBterabyte
10005PBpetabyte
10006EBexabyte
10007ZBzettabyte
10008YByottabyte
Binary
ValueJEDECIEC
1024KBkilobyteKiBkibibyte
10242MBmegabyteMiBmebibyte
10243GBgigabyteGiBgibibyte
10244--TiBtebibyte
10245--PiBpebibyte
10246--EiBexbibyte
10247--ZiBzebibyte
10248--YiByobibyte
Orders of magnitude of data
 
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Multiples of bytes
Decimal
ValueMetric
1000kBkilobyte
10002MBmegabyte
10003GBgigabyte
10004TBterabyte
10005PBpetabyte
10006EBexabyte
10007ZBzettabyte
10008YByottabyte
Binary
ValueJEDECIEC
1024KBkilobyteKiBkibibyte
10242MBmegabyteMiBmebibyte
10243GBgigabyteGiBgibibyte
10244--TiBtebibyte
10245--PiBpebibyte
10246--EiBexbibyte
10247--ZiBzebibyte
10248--YiByobibyte
Orders of magnitude of data

The kilobyte is a multiple of the unit byte for digital information. Although the SI 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, when referring to data transfer rates[4] and to disk storage space,[5] "kilobyte" means 1000 (103) bytes. On the other hand, random-access memory capacity such as CPU cache measurements are always stated in multiples of 1024 (210) bytes, due to memory's binary addressing.

In the International System of Quantities, the kilobyte (symbol kB) is 1000 bytes, while the kibibyte (symbol KiB) is 1024 bytes. The binary representation of 1024 bytes typically uses the symbol KB, with an uppercase K. Informally, the B is sometimes dropped, with the leftover K representing 1024 bytes; this variant, however, is not standardized and may be used arbitrarily. All existing recommendations prefer to use the uppercase letter B for byte, because b is used for the bit.

Definitions[edit]

The unit kilobyte is commonly used to indicate either 1000 or 1024 bytes. The value 1024 originated as compromise technical jargon for the byte multiples that needed to be expressed by 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) enacted standards for binary prefixes, specifying the use of kilobyte to strictly denote 1000 bytes and kibibyte to denote 1024 bytes. By 2007, the IEC Standard had been adopted by the IEEE, EU, and NIST and is now part of the International System of Quantities. Nevertheless, the term kilobyte continues to be widely used with both of the following two meanings:

Examples[edit]

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.[17]

See also[edit]

Notes[edit]

  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. ^ Conversion of Data Transfer Rate Units
  5. ^ 1977 Disk/Trend Report Rigid Disk Drives, published June 1977
  6. ^ Prefixes for Binary Multiples — The NIST Reference on Constants, Units, and Uncertainty
  7. ^ SanDisk USB Flash Drive "Note: 1 megabyte (MB) = 1 million bytes; 1 gigabyte (GB) = 1 billion bytes."
  8. ^ "How Mac OS X reports drive capacity". Apple Inc. 2009-08-27. Retrieved 2009-10-16. 
  9. ^ 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." 
  10. ^ Frankenberg, Robert (October 1974). "All Semiconductor Memory Selected for New Minicomputer Series" (PDF). Hewlett-Packard Journal (Hewlett-Packard) 26 (2): pg 15–20. Retrieved 2007-06-18. "196K-word memory size" 
  11. ^ Hewlett-Packard (November 1973). "HP 3000 Configuration Guide" (PDF). HP 3000 Computer System and Subsystem Data: pg 59. Retrieved 2010-01-22. 
  12. ^ "SA400 minifloppy". Swtpc.com. 2013-08-14. Retrieved 2014-03-25. 
  13. ^ http://www.swtpc.com/mholley/SA400/SA400_Datasheet.pdf
  14. ^ http://bitsavers.org/pdf/dec/disc/rx01/EK-RX01-MM-002_maint_Dec76.pdf
  15. ^ "Determining Actual Disk Size: Why 1.44 MB Should Be 1.40 MB". Support.microsoft.com. 2003-05-06. Retrieved 2014-03-25. 
  16. ^ "How OS X and iOS report storage capacity". Support.apple.com. 2013-07-01. Retrieved 2014-03-25. 
  17. ^ 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[edit]

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