Xref: utzoo comp.unix.msdos:147 comp.lang.apl:537
Path: utzoo!attcan!uunet!jorel!jmcook
From: jmcook@jorel.APLDMT.COM (joel m. cook)
Newsgroups: comp.unix.msdos,comp.lang.apl
Subject: Anomalous integer arithmetic--Simul-Task/Native DOS
Keywords: Simul-Task, unix, APL
Message-ID: <283@jorel.APLDMT.COM>
Date: 26 Oct 90 20:33:06 GMT
Followup-To: poster
Organization: Applied Materials, Inc., Santa Clara, CA
Lines: 25

I'm running STSC's APL*PLUS/PC Version 8.0 and I get differing 
behaviors with integer arithmetic depending on whether or
not I'm running native DOS or Simul-Task under AT&T SVR3.2.1.

If I add 32767 to 1, I get -32768 under Simul-Task, but
32769 under native DOS.  I.e., 

	32767 + 1 -> -32768  APL under Simul-Task
	32767 + 1 -> 32768 APL under native DOS.

If I use floating point (32767.00000000001 for instance), it
all works as it should.  Seems to me that under Simul-Task
the results are being kept in 2's-complement 16 bit notation, but
are handled properly under native DOS.  Since I thought 
the whole point of Simul-Task was to be a virtual 8086, I
don't understand the discrepancy.

For what it's worth, when run under Windows 3.0, the correct
answer is given, so it appears not to be *just* a function
of the virtual 8086 (assuming that's what Windows does???).

Any enlightenment will, as usual, be most appreciated!
-- 
			Joel M. Cook
			jmcook@jorel.apldmt.com