In December1998 the International Electrotechnical Commission (IEC), the leading internationalorganization for worldwide standardization in electrotechnology, approvedas an IEC International Standard names and symbols for prefixes for binarymultiples for use in the fields of data processing and data transmission.The prefixes are as follows:
[attach]1638276[/attach]
It issuggested that in English, the first syllable of the name of the binary-multipleprefix should be pronounced in the same way as the first syllable of thename of the corresponding SI prefix, and that the second syllable shouldbe pronounced as "bee."
It isimportant to recognize that the new prefixes for binary multiples are notpart of the International System of Units (SI), the modern metric system.However, for ease of understanding and recall, they were derived from theSI prefixes for positive powers of ten. As can be seen from the above table,the name of each new prefix is derived from the name of the correspondingSI prefix by retaining the first two letters of the name of the SI prefixand adding the letters "bi," which recalls the word "binary." Similarly,the symbol of each new prefix is derived from the symbol of the correspondingSI prefix by adding the letter "i," which again recalls the word "binary."(For consistency with the other prefixes for binary multiples, the symbolKi is used for 210 rather than ki.)
[size=+1]Official publication
Theseprefixes for binary multiples, which were developed by IEC Technical Committee(TC) 25, Quantities and units, and their letter symbols, with the strongsupport of the International Committee for Weights and Measures (CIPM)and the Institute of Electrical and Electronics Engineers (IEEE), were firstadopted by the IEC as Amendment 2 to IEC International Standard IEC 60027-2: Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics. The full content of Amendment 2, which has a publication date of 1999-01, is reflected in the tables above and the suggestion regarding pronunciation. Subsequently the contents of this Amendment were incorportated in the second edition of IEC 60027-2, which has a publication date of 2000-11 (the first edition was published in 1972). The complete citation for this revised standard isIEC 60027-2, Second edition, 2000-11, Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics.
Historicalcontext*
Onceupon a time, computer professionals noticed that 210 was verynearly equal to 1000 and started using the SI prefix "kilo" to mean 1024.That worked well enough for a decade or two because everybody who talkedkilobytes knew that the term implied 1024 bytes. But, almost overnighta much more numerous "everybody" bought computers, and the trade computerprofessionals needed to talk to physicists and engineers and even to ordinarypeople, most of whom know that a kilometer is 1000 meters and a kilogramis 1000 grams.
Then data storage for gigabytes, and even terabytes, became practical, and thestorage devices were not constructed on binary trees, which meant that,for many practical purposes, binary arithmetic was less convenient thandecimal arithmetic. The result is that today "everybody" does not "know"what a megabyte is. When discussing computer memory, most manufacturersuse megabyte to mean 220 = 1 048 576 bytes, but the manufacturers of computer storage devices usually use the term to mean 1 000 000 bytes. Some designers of local area networks have used megabit per second to mean 1 048 576 bit/s, but all telecommunications engineers use it to mean 106 bit/s. And if two definitions of the megabyte are not enough, a third megabyte of 1 024 000 bytes is the megabyte used to format the familiar 90 mm (3 1/2 inch), "1.44 MB" diskette. The confusion is real, as is the potential for incompatibility in standards and in implemented systems.
Facedwith this reality, the IEEE Standards Board decided that IEEE standardswill use the conventional, internationally adopted, definitions of theSI prefixes. Mega will mean 1 000 000, except that the base-twodefinition may be used (if such usage is explicitly pointed out on a case-by-casebasis) until such time that prefixes for binary multiples are adopted byan appropriate standards body.
