Kilobyte

Decimal (1000 bytes) In the International System of Units (SI) the metric prefix kilo means 1,000 (103); therefore, one kilobyte is 1000 bytes. The unit symbol is kB. This is the definition standardised by the International Electrotechnical Commission (IEC). This definition, and the related definitions of the prefixes mega (), giga (), etc., are most commonly used for data transfer rates in computer networks, internal bus, hard drive and flash media transfer speeds, and for the capacities of most storage media, particularly hard disk drives, flash-based storage, and DVDs. It is also consistent with the other uses of the metric prefixes in computing, such as CPU clock speeds or measures of performance. The international standard IEC 80000-13 uses the term "byte" to mean eight bits (1 B = 8 bit). Therefore, 1 kB = 8000 bit. One thousand kilobytes (1000 kB) is equal to one megabyte (1 MB), where 1 MB is one million bytes. Binary (1024 bytes) The term kilobyte has traditionally been used to refer to 1024 bytes (210 B). The usage of the metric prefix kilo for binary multiples arose as a convenience, because 1024 is approximately 1000. The binary interpretation of metric prefixes is still prominently used by the Microsoft Windows operating system. Binary interpretation is also used for random-access memory capacity, such as main memory and CPU cache size, due to the prevalent binary addressing of memory. The binary meaning of the kilobyte for 1024 bytes typically uses the symbol KB, with an uppercase letter K. The B is sometimes omitted in informal use. For example, a processor with 65,536 bytes of cache memory might be said to have "64 K" of cache. In this convention, one thousand and twenty-four kilobytes (1024 KB) is equal to one megabyte (1 MB), where 1 MB is 10242 bytes. In December 1998, the IEC addressed such multiple usages and definitions by creating prefixes such as kibi, mebi, gibi, etc., to unambiguously denote powers of 1024. Thus the kibibyte, symbol KiB, represents 210 bytes = 1024 bytes. These prefixes are now part of IEC 80000-13. The IEC further specified that the kilobyte should only be used to refer to 1000 bytes. The International System of Units restricts the use of the SI prefixes strictly to powers of 10. ==Use of term==

• The Shugart SA-400 5-inch floppy disk (1976) held 109,375 bytes unformatted, and was advertised as "110 Kbyte", using the 1000 convention. Likewise, the 8-inch DEC RX01 floppy (1975) held 256,256 bytes formatted, and was advertised as "256k". On the other hand, the Tandon 5-inch DD floppy format (1978) held 368,640 (which is 360×1024) bytes, but was advertised as "360 KB", following the 1024 convention. • Early home computer systems would often advertise using the 1024 convention, hence the naming of the Commodore 64, Commodore 128, and the Amstrad CPC 464. • On modern systems, all versions of Microsoft Windows divide by 1024 and represent a 65,536-byte file as "64 KB". file sizes are reported with decimal prefixes. • the binary interpretation was still used in marketing and billing by some telecommunication companies, such as Vodafone, AT&T, Orange and Telstra. == Data examples ==

• The Lord's Prayer, in Latin, is 296 bytes (about 0.3 kilobytes). • The short story The Gift of the Magi, by O. Henry, hosted on Project Gutenberg as an uncompressed plain text file, is 11,203 characters; this is 11.2 kilobytes (dividing by 1,000) or 10.94 kibibytes (dividing by 1,024). The Cask of Amontillado, by Edgar Allan Poe, is 12,843 bytes (12.8 kilobytes or 12.5 kibibytes). • The size of this article's wikitext source, as of , is kilobytes. • The novel The Picture of Dorian Gray, by Oscar Wilde, hosted on Project Gutenberg as an uncompressed plain text file, is 428,952 bytes; this is 428.95 kilobytes (428,952 divided by 1,000) and 418.90 kibibytes (divided by 1,024). Great Expectations is 994,639 bytes (994.639 kB), and Moby Dick is 1,191,763 bytes (1,191.763 kB). ==See also==