diff --git a/entries/quantifiers.txt b/entries/quantifiers.txt index b34140f..0bc988b 100644 --- a/entries/quantifiers.txt +++ b/entries/quantifiers.txt @@ -1,4 +1,77 @@ quantifiers -Prev Up Next quadruple bucky Home quantum bogodynamics +In techspeak and jargon, the standard metric prefixes used in the SI (Systeme +International) conventions for scientific measurement have dual uses. With +units of time or things that come in powers of 10, such as money, they retain +their usual meanings of multiplication by powers of 1000 = 10^3. But when used +with bytes or other things that naturally come in powers of 2, they usually +denote multiplication by powers of 1024 = 2^10. +Here are the SI magnifying prefixes, along with the corresponding decimal +interpretations in common use: + +kilo (K, KB) 1,024 +mega (M, MB) 1,048,576 +giga (G, GB) 1,073,741,824 +tera (T, TB) 1,099,511,627,776 +peta (P, PB) 1,125,899,906,842,624 +exa (EX) 1,152,921,504,606,846,976� +zetta 1,180,591,620,717,411,303,424 +yotta 1,208,925,819,614,629,174,706,176 + +Here are the SI fractional prefixes: + +milli 1000^-1 +micro 1000^-2 +nano 1000^-3 +pico 1000^-4 +femto 1000^-5 +atto 1000^-6 +zepto 1000^-7 +yocto 1000^-8 + +The prefixes zetta-, yotta-, zepto-, and yocto- have been included in these +tables purely for completeness and giggle value; they were adopted in 1990 +by the 19th Conference Generale des Poids et Mesures. The binary peta- +and exa- loadings, though well established, are not in jargon use either +— yet. The prefix milli-, denoting multiplication by 1/1000, has always +been rare in jargon (there is, however, a standard joke about the +millihelen — notionally, the amount of beauty required to launch one +ship). See the entries on micro-, pico-, and nano- for more information +on connotative jargon use of these terms. ‘Femto’ and ‘atto’ (which, +interestingly, derive not from Greek but from Danish) have not yet +acquired jargon loadings, though it is easy to predict what those will be +once computing technology enters the required realms of magnitude +(however, see attoparsec). + +There are, of course, some standard unit prefixes for powers of 10. In +the following table, the ‘prefix’ column is the international standard +prefix for the appropriate power of ten; the ‘binary’ column lists +jargon abbreviations and words for the corresponding power of 2. The +B-suffixed forms are commonly used for byte quantities; the words ‘meg’ +and ‘gig’ are nouns that may (but do not always) pluralize with ‘s’. + +Confusingly, hackers often use K or M as though they were suffix or +numeric multipliers rather than a prefix; thus “2K dollars”, “2M of +disk space”. This is also true (though less commonly) of G. + +Note that the formal SI metric prefix for 1000 is ‘k’; some use this +strictly, reserving ‘K’ for multiplication by 1024 (KB is thus +‘kilobytes’). + +K, M, and G used alone refer to quantities of bytes; thus, 64G is +64 gigabytes and ‘a K’ is a kilobyte (compare mainstream use of +‘a G’ as short for ‘a grand’, that is, $1000). Whether one +pronounces ‘gig’ with hard or soft ‘g’ depends on what one thinks +the proper pronunciation of ‘giga-’ is. + +Confusing 1000 and 1024 (or other powers of 2 and 10 close in +magnitude) — for example, describing a memory in units of 500K or +524K instead of 512K — is a sure sign of the marketroid. One example +of this: it is common to refer to the capacity of 3.5" floppies +as ‘1.44 MB’ In fact, this is a completely bogus number. The +correct size is 1440 KB, that is, 1440 * 1024 = 1474560 bytes. +So the ‘mega’ in ‘1.44 MB’ is compounded of two ‘kilos’, one of +which is 1024 and the other of which is 1000. The correct number +of megabytes would of course be 1440 / 1024 = 1.40625. Alas, this +fine point is probably lost on the world forever. \ No newline at end of file