World Wide Words

From the Turns of Phrase section

Kibibyte

Because of the binary nature of computing, it has long been common for memory sizes, disk capacities and the like to be measured, not in units of 1,000, but of 1,024 (the latter being 2 to the power of 10). Lacking a name for their idiosyncratic multiple, computer scientists borrowed the standard metric prefix for 1,000, kilo-. This was fine while such matters were the preserve solely of a few computer experts, but now we’re all using the things, the confusion between the two senses of the prefix is getting to be a problem. The International Electrotechnical Commission (IEC), a standards body, is proposing a new set of prefixes to sort matters out. Multiples of 1,024 would be prefixed by kibi-, for example kibibytes. Similarly mebi-, gibi- and tebi- would replace mega-, giga- and tera-. These prefixes are formed using the first two letters of the existing ones, plus bi (short for binary). We’re several years away from any decisions on this one, though, and probably a great deal further away from their general acceptance.

A proposal being circulated internationally by the IEC would introduce the new prefixes kibi, mebi, gibi and tebi derived as short unions of the SI prefixes with the word “binary.”

IEEE Standards Bearer, Jan. 1997

The new term “kibibyte” will more accurately describe the number of bytes in a kilobyte — rather than being 1,000, as could be inferred by the prefix “kilo,” a kilobyte actually has 1,024 (2 to the 10th power) bytes.

Edupage, Mar. 1999