Date: Fri, 17 Mar 1995 00:47:02 +0900
From: Stephen Turnbull <turnbull AT shako DOT sk DOT tsukuba DOT ac DOT jp>
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: DOS multi-tasking, Ada and djgpp]

   >I am very excited about GNAT and the (upcoming) validation testing.  I
   >am sorry to hear that (as I read in the documentation) the DOS version
   >does not support tasking.  I hope that is rectified soon.  Dos will be
   >my primary Ada platform for a while.

   You must be one heck of an optimist.  DOS was designed from the
   ground up to be unitasking (monotasking?), and making it anything
   else is nontrivial.

0.9-tasking, just like the DPMI standard used by Windows.  DOS wasn't
designed, as I understand it (not in the sense that even Linux was
designed).  It just sort of grew in the fertile brain of an
acquaintance of Bill Gates, who turned it into the path to more money
than Midas ever dreamed of.

Pot-shots aside, despite the fact that DOS is a system full of patches
to kludges on crocks on hacks, DESQview and DESQview/X make it look an
awful lot like a multi-tasking system.  And does a fairly good job of
limiting the number of system crashes.  One should be able to build
IPC and so on on top of DV API calls.  But...

Somebody has to own the hardware.  That is going to be the operating
system, and this means that every time you access the floppy disk (for
example) the system is going to drop dead, since DOS not only isn't
multi-tasking, it's not reentrant, so you can't access more than one
DOS service simultaneously.  Yes, it's possible to get around this
(basically by writing your own drivers for all the hardware you need
to access), but you may as well install Linux or *BSD if you want a
general-purpose solution.

So, as Aaron says, don't hold your breath waiting for DJGPP+GNAT to
give you Indy performance on your 386/SX, or even your Pentium 90 with
catsup and all the trimmings.

-- 
Stephen Turnbull  /  Yaseppochi-gumi  /  <turnbull AT shako DOT sk DOT tsukuba DOT ac DOT jp>
http://turnbull.sk.tsukuba.ac.jp/      anon FTP: turnbull.sk.tsukuba.ac.jp
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