77 lines
3.6 KiB
Plaintext
77 lines
3.6 KiB
Plaintext
quantifiers
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In techspeak and jargon, the standard metric prefixes used in the SI (Systeme
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International) conventions for scientific measurement have dual uses. With
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units of time or things that come in powers of 10, such as money, they retain
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their usual meanings of multiplication by powers of 1000 = 10^3. But when used
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with bytes or other things that naturally come in powers of 2, they usually
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denote multiplication by powers of 1024 = 2^10.
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Here are the SI magnifying prefixes, along with the corresponding decimal
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interpretations in common use:
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kilo (K, KB) 1,024
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mega (M, MB) 1,048,576
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giga (G, GB) 1,073,741,824
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tera (T, TB) 1,099,511,627,776
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peta (P, PB) 1,125,899,906,842,624
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exa (EX) 1,152,921,504,606,846,976<37>
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zetta 1,180,591,620,717,411,303,424
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yotta 1,208,925,819,614,629,174,706,176
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Here are the SI fractional prefixes:
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milli 1000^-1
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micro 1000^-2
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nano 1000^-3
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pico 1000^-4
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femto 1000^-5
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atto 1000^-6
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zepto 1000^-7
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yocto 1000^-8
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The prefixes zetta-, yotta-, zepto-, and yocto- have been included in these
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tables purely for completeness and giggle value; they were adopted in 1990
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by the 19th Conference Generale des Poids et Mesures. The binary peta-
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and exa- loadings, though well established, are not in jargon use either
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— yet. The prefix milli-, denoting multiplication by 1/1000, has always
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been rare in jargon (there is, however, a standard joke about the
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millihelen — notionally, the amount of beauty required to launch one
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ship). See the entries on micro-, pico-, and nano- for more information
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on connotative jargon use of these terms. ‘Femto’ and ‘atto’ (which,
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interestingly, derive not from Greek but from Danish) have not yet
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acquired jargon loadings, though it is easy to predict what those will be
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once computing technology enters the required realms of magnitude
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(however, see attoparsec).
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There are, of course, some standard unit prefixes for powers of 10. In
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the following table, the ‘prefix’ column is the international standard
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prefix for the appropriate power of ten; the ‘binary’ column lists
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jargon abbreviations and words for the corresponding power of 2. The
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B-suffixed forms are commonly used for byte quantities; the words ‘meg’
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and ‘gig’ are nouns that may (but do not always) pluralize with ‘s’.
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Confusingly, hackers often use K or M as though they were suffix or
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numeric multipliers rather than a prefix; thus “2K dollars”, “2M of
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disk space”. This is also true (though less commonly) of G.
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Note that the formal SI metric prefix for 1000 is ‘k’; some use this
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strictly, reserving ‘K’ for multiplication by 1024 (KB is thus
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‘kilobytes’).
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K, M, and G used alone refer to quantities of bytes; thus, 64G is
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64 gigabytes and ‘a K’ is a kilobyte (compare mainstream use of
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‘a G’ as short for ‘a grand’, that is, $1000). Whether one
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pronounces ‘gig’ with hard or soft ‘g’ depends on what one thinks
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the proper pronunciation of ‘giga-’ is.
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Confusing 1000 and 1024 (or other powers of 2 and 10 close in
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magnitude) — for example, describing a memory in units of 500K or
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524K instead of 512K — is a sure sign of the marketroid. One example
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of this: it is common to refer to the capacity of 3.5" floppies
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as ‘1.44 MB’ In fact, this is a completely bogus number. The
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correct size is 1440 KB, that is, 1440 * 1024 = 1474560 bytes.
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So the ‘mega’ in ‘1.44 MB’ is compounded of two ‘kilos’, one of
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which is 1024 and the other of which is 1000. The correct number
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of megabytes would of course be 1440 / 1024 = 1.40625. Alas, this
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fine point is probably lost on the world forever. |