quantifiers
1 definition found
quantifiers - Jargon File (4.4.4, 14 Aug 2003) :
quantifiers
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
binary interpretations in common use:
prefix decimal binary
kilo- 1000^1 1024^1 = 2^10 = 1,024
mega- 1000^2 1024^2 = 2^20 = 1,048,576
giga- 1000^3 1024^3 = 2^30 = 1,073,741,824
tera- 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
Here are the SI fractional prefixes:
prefix decimal jargon usage
milli- 1000^-1 (seldom used in jargon)
micro- 1000^-2 small or human-scale (see micro-)
nano- 1000^-3 even smaller (see nano-)
pico- 1000^-4 even smaller yet (see pico-)
femto- 1000^-5 (not used in jargon--yet)
atto- 1000^-6 (not used in jargon--yet)
zepto- 1000^-7 (not used in jargon--yet)
yocto- 1000^-8 (not used in jargon--yet)
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'.
prefix decimal binary pronunciation}
kilo- k K, KB, kay
mega- M M, MB, meg meg
giga- G G, GB, gig gig,jig
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. [1993 update: hacker Morgan Burke
has proposed, to general approval on Usenet, the following additional
prefixes:
groucho 10^-30
harpo 10^-27
harpi 10^27
grouchi 10^30
We observe that this would leave the prefixes zeppo-, gummo-, and
chico- available for future expansion. Sadly, there is little
immediate prospect that Mr. Burke's eminently sensible proposal will
be ratified.]
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