IBM COBOL & REENTRANT code (was: Confessions of an "OO Foreigner"

From: William M. Klein (wmklein_at_nospam.netcom.com)
Date: 12/30/03 

Date: Tue, 30 Dec 2003 16:39:08 GMT

"Peter E.C. Dashwood" <dashwood@enternet.co.nz> wrote in message
news:3ff136b8_2@news.athenanews.com...
> "William M. Klein" <wmklein@nospam.netcom.com> wrote in message
> news:Mm3Ib.25364$Pg1.10164@newsread1.news.pas.earthlink.net...
<snip>

> > It should be noted here, that CICS programming (at least as long as I have
> known
> > it - and I cam in when macro was first being "phased out") has ALWAYS been
> > "event driven". So for those using OO in a GUI (or possibly other)
> > environments, being "event driven" is no "biggy" change in what COBOL can
> (and
> > does) do.
>
> It should be noted that IBM does NOT implement (true) re-entrant code in
> COBOL (to do so, COBOL would need to save and restore the system state when
> system interrupts occur. While this is possible in BAL, there are no direct
> facilities for doing it in COBOL). The code used with both CICS and IMS/DC
> (as it was), is "serially re-usable". The difference is subtle, but
> important.

Not truly relevant to an OO discussion, but IBM has offered a "truly re-entrant"
option for COBOL since the mid '80's - ever since VS COBOL II was introduced
(even before it was fully '85 Standard conforming). The "serially reusable"
restriction WAS true for OS/VS COBOL, but hasn't been for a couple of decades
now. (The compiler creates code that is "not self modifying" but modifies only
a copy (one per instance) of data.) 

-- 
Bill Klein
 wmklein <at> ix.netcom.com

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