Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!stan!imp
From: imp@Solbourne.COM (Warner Losh)
Newsgroups: comp.os.msdos.programmer
Subject: Re: TSR PROGRAMMING PROBLEM
Message-ID: <1991Jan30.063551.26067@Solbourne.COM>
Date: 30 Jan 91 06:35:51 GMT
References: <1991Jan29.173752.10045@bronze.ucs.indiana.edu> <5369@trantor.harris-atd.com> <2168@njitgw.njit.edu>
Organization: Solbourne Computer, Inc., Longmont, CO
Lines: 30

In article <2168@njitgw.njit.edu> cd5340@mars.njit.edu (Charlap) writes:
>Not quite.  DOS re-enters itself all over the place.  There is a scheduler
>interrupt (I forget what it is, though) which is very undocumented, which
>many hackers use for making re-entrant TSR's.  Most notable of these is the
>DOS PRINT command, which uses the scheduler interrupt in order to do background
>printing.

Not quite. :-)

There is a wonderful book on the underside and hidden corners of DOS
called Undocumented DOS by a whole bunch of people whose names I can't
remember (except for Ralf Brown of the interrupt list fame).  It goes
into enough detail that you can write a TSR that has a prayer of
working in many environments (and not just the current machine that
you are on).  It also goes into lots of other things like network
redirectors and trapping interrupts.  It comes with two disks full of
programs.  All in all, a good book.

Oh yah, most Waite Group books that I have seen aren't worth the paper
they are printed on.  They contain enough errors and misleading
information to be very frustrating to use.  However, the MS-DOS
Developers Guide by them is better about this than most.

I'd go into more details, but _Undocumented_DOS_ does a much better
job than I could possibly do here.

Warner
-- 
Warner Losh		imp@Solbourne.COM
We sing about Beauty and we sing about Truth at $10,000 a show.