Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!agate!usenet.ins.cwru.edu!cwlim!trier
From: trier@cwlim.INS.CWRU.Edu (Stephen C. Trier)
Newsgroups: comp.os.msdos.programmer
Subject: Re: TSR PROGRAMMING PROBLEM
Message-ID: <1991Feb12.064710.25412@usenet.ins.cwru.edu>
Date: 12 Feb 91 06:47:10 GMT
References: <1991Jan31.185355.10599@everexn.com> <1570@pdxgate.UUCP>
Sender: news@usenet.ins.cwru.edu
Reply-To: trier@po.CWRU.Edu
Organization: Case Western Reserve Univ. Cleveland, Ohio, (USA)
Lines: 31
Nntp-Posting-Host: cwlim.ins.cwru.edu

In article <1570@pdxgate.UUCP> mwizard@eecs.cs.pdx.edu (Craig Nelson) writes:
>	Anyone telling you DOS is not reentrant is blowing off cobwebs they
>collected the last time they tried to think.

Thank you, Craig.  I appreciate the compliment.

DOS is not "reentrant" in the same sense as an operating system like OS-9.
In such an operating system, almost everything is reentrant.  (Certain
portions of device drivers do not need to be.)  If MS-DOS were reentrant
to that extreme, writing a TSR would be trivial.

Of course, some portions of the real-world MS-DOS are reentrant.  I would
hope they were, since it is very hard to write an operating system that has
no reentrancy.  However, the reentrancy is, in general, of a limited
nature.  The most useful calls, like the file handle I/O functions, are
_not_ reentrant.  It's this deficiency that makes TSR programming tricky.

Essentially, the statement "DOS is not reentrant" probably refers to the
MS-DOS function-call interface, which is largely _not_ reentrant.  I think
that any person making such a statement would know as well as you that
some portions of MS-DOS are reentrant.  It's just that other parts of MS-DOS,
the high-level parts most useful to a programmer, are not.

Incidentally, your point could have been made just as effectively without
the insult.

-- 
Stephen Trier                              Case Western Reserve University
Work: trier@cwlim.ins.cwru.edu             Information Network Services
Home: sct@seldon.clv.oh.us               %% Any opinions above are my own. %%