On Fri, 25 Sep 2009 16:52:04 -0500, William H. Blair
<[email protected]> wrote:
. . .
>
>The short version: Yes, essentially, it has been like that forever,
>or indeed at least "long enough" that his intended point was valid.
>
>The long version:
>
>I don't know about "that field" specifically, since I'm not a CICS
>guy, either. But I just looked at some code I last touched in 1978
>and I see it supported the century indicator. Some evidence at hand
>indicates that I was first exposed to the internals of CICS around
>1981-1982, so for me that idea was not likely to have specifically
>been derived from CICS internals.
>
>I don't remember where or when the fact that the 2nd nybble in the
>classic OS/VS date value is the century indicator (or that the "cc"
>in "ccyydddS" is the century byte) came from. But after all this is
>the date representation that has been returned by TIME LINKAGE=SVC
>for a long time. Perhaps Peter Relson or some other IBMer would be
>able to enlighten us about when (I predict it arrived on the scene
>in the MVS/SP 1.2 or 1.3 timeframe, but that's just a guess, here).
>
I have admitted that I am no authority on CICS, so it was pure speculation on
my part that the field in question could be direct copy of the date as provided
by the TIME macro.
If CICS really did have a "century indicator" in there in 1978, then although
it
is in a similar format, it could not have been simply copied from the value
returned by the TIME macro.
>From the description of the TIME macro in GC28-0683-3, OS/VS2 MVS
Supervisor Services and Macro Instructions, 1983 (thanks to Bitsavers):
"The date is returned in register 1 as packed decimal digits of the form
00YYDDDF, where: YY is the last two digits of the year
DDD is the day of the year
F is a 4-bit sign character that allows the
data to be
unpacked and printed"
I believe the century indicator did not make an appearance, as far as the
TIME macro is concerned, until much later in the eighties. During the Y2K
frenzy of the late nineties, I still had a manual dated something like 1987,
that
showed the high byte as 00. If the century indicator concept existed well
before then, it leaves me wondering where they got the actual value from if
the operating system did not provide it (other than perhaps via the TOD/STCK
value). Maybe they were just optimists and figured that by the time they
really needed it, the operating system would have been updated to provide it.
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