Those are kibibyte and
mebibyte.
Although consistent, in a
sense, with SI, they are not SI. Rather, they are the object of an IEC
(International Electrotechnical Commission) standard, written in 1998 (see
http://physics.nist.gov/cuu/Units/binary.html).
It's never acceptable (at
least to the SI purist) to use KB; that should be kB. However, the capital K is
used for the binary version (KiB).
The choice of the binary
or the standard prefix is dependent on the structure. As memory capacity is
always a power of 2 (because of its structure), the binary prefix is always
appropriate. As data communication speeds are always expressed decimally (except
by those who don't know better), the binary prefix is never appropriate. Disk
storage is a gray area. However, if you express its capacity as a decimal
number, then the SI prefix applies. If you express it as a power of 2 (that
power being 10, 20, 30, etc.), then the binary prefix
applies.
Getting the world to use
binary prefixes (as opposed to using SI prefixes ambiguously) for things like
memory size is, of course, another matter.
Finally, with respect to
the file you're downloading, if it's something like 4 700 000 bytes, 4.7 GB is
correct. If it's about 4.7 times 1 048 576, then 4.7 GiB is
correct.
Bill Potts,
CMS
Roseville, CA
http://metric1.org [SI Navigator]
-----Original Message-----Recently I was downloading a Linux distribution off Bittorrent and happened to notice that in the software I use for it there was an option to use SI units meaning KiB for Kilobyte and MiB for Megabyte instead of KB and MB. What I don't get is why it's not acceptable to use the KB or MB. Wikipedia seems to indicate from this link http://en.wikipedia.org/wiki/Byte that either one is acceptable
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]On Behalf Of Mike Millet
Sent: Sunday, May 14, 2006 08:14
To: U.S. Metric Association
Subject: [USMA:36781] SI in computer file sizes
.
Just as a side note the file I'm downloading happens to be 4.7GiB :). It's going to take a while so I'll have plenty of time to stare at the number and ponder it.
Mike
--
"The boy is dangerous, they all sense it why can't you?"
