SI PREFIX
\sˈiː pɹˈiːfɪks], \sˈiː pɹˈiːfɪks], \s_ˈiː p_ɹ_ˈiː_f_ɪ_k_s]\
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The standard metric prefixes used in theSystÃ¨me International d'UnitÃ©s (SI) conventions forscientific measurement.Here are the SI magnifying prefixes, along with thecorresponding binary interpretations in common use: prefix abr decimal binary yocto 1000^8 zepto 1000^7 atto 1000^6 femto f 1000^5 pico p 1000^4 nano n 1000^3 micro * 1000^2 * Abbreviation: Greek mu milli m 1000^1 kilo k 1000^1 1024^1 = 2^10 = 1,024 mega M 1000^2 1024^2 = 2^20 = 1,048,576 giga G 1000^3 1024^3 = 2^30 = 1,073,741,824 tera T 1000^4 1024^4 = 2^40 = 1,099,511,627,776 peta 1000^5 1024^5 = 2^50 = 1,125,899,906,842,624 exa 1000^6 1024^6 = 2^60 = 1,152,921,504,606,846,976 zetta 1000^7 1024^7 = 2^70 = 1,180,591,620,717,411,303,424 yotta 1000^8 1024^8 = 2^80 = 1,208,925,819,614,629,174,706,176"Femto" and "atto" derive not from Greek but from Danish.The abbreviated forms of these prefixes are common inelectronics and physics.When used with bytes of storage, these prefixes usually denotemultiplication by powers of 1024 = 2^10 (K, M, G and T arecommon in computing). Thus "MB" stands for megabytes (2^20bytes). This common practice goes against the edicts of theBIPM who deprecate the use of these prefixes for powers oftwo. The formal SI prefix for 1000 is lower case "k"; some,including this dictionary, use this strictly, reserving uppercase "K" for multiplication by 1024 (KB is thus "kilobytes").Also, in data transfer rates the prefixes stand for powers often so, for example, 28.8 kb/s means 28,800 bits per second.The unit is often dropped so one may talk of "a 40K salary" (40000 dollars) or "2 meg of disk space" (2*2^20 bytes).The accepted pronunciation of the initial G of "giga" ishard, /gi'ga/.Confusing 1000 and 1024 (or other powers of 2 and 10 close inmagnitude)  for example, describing a memory in units of 500Kor 524K instead of 512K  is a sure sign of the marketroid.For example, 3.5" microfloppies are often described asstoring "1.44 MB". In fact, this is completely specious. Thecorrect size is 1440 KB = 1440 * 1024 = 1474560 bytes. Alas,this point is probably lost on the world forever.In 1993, hacker Morgan Burke proposed, to general approval onUsenet, the following additional prefixes: groucho (10^30),harpo (10^27), harpi (10^27), grouchi (10^30). This wouldleave the prefixes zeppo, gummo, and chico available forfuture expansion. Sadly, there is little immediate prospectthat Mr. Burke's eminently sensible proposal will be ratified.
By Denis Howe