W dniu 2019-10-29 o 17:58, Paul Gilmartin pisze:
On Tue, 29 Oct 2019 11:58:00 -0400, Steve Smith wrote:
OK, after I found my old 3390 reference card, and doing the math, I proved
that DCOLLECT is indeed using 2**10 to mean kilo- (and presumably 2**20 for
mega-). I found a 3390-3 (I think) with 3,339 cylinders, and multiplied by
849,960 (bytes/cyl) and got 2838016440, which /1024 = 2771500.4296875.
DCOLLECT shows 2,771,500. QED.
In "Glossary of z/OS terms and abbreviations" (no title page nor part #;
apparently for z/OS 2.3) I see the (somewhat garbled):
megabyte (MB). 220 bytes, 1 048 576 bytes.,048,576 bytes.
??? (sic)
I find no similar entry, correct or incorrect, for "kilo*".
I wonder which convention IBM uses when it specifies the
shipping weight of a z in kilograms? If IBM can flout SI in
some cases, why not in all?
Gil,
It's quite easy. Dualism of kilo as 1000 or maybe 1024 exists only in IT
world, exactly in memory (RAM, disk, etc.).
So kilograms are obvoiusly clear. The same for GHz of CPU frequency.
Some habit/practice say binary prefixes are for RAM (memory), while
decimal are used for disks and tapes (external storage), but this is not
always true. In many cases programs provides disk information using
"binary" megabytes.
Of course there are special prefixes for binary: KiB, MiB, GiB. Or just
Ki, Mi, Gi. This is unambigous even if you want to tell us about weight
- Kig = 1024 grams. Very rare, but unambigous.
What remains ambigous is kB, MB, GB - memory size. You never know
whether it is intentional decimal prefix, or just author ignored
existence of Ki, Mi, Gi, Ti, Pi...
Regarding DCOLLECT - I have no idea. :-)
Regards
--
Radoslaw Skorupka
Lodz, Poland
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