From:	"Jan Humme" <info AT imedia-engineering DOT nl>
Newsgroups:	comp.os.msdos.djgpp
Subject:	How do I gracefully terminate my TSR application?
Date:	14 Jun 1998 14:58:38 GMT
Organization:	Imedia Engineering BV
Lines:	38
Message-ID:	<6m0oeu$c94@news3.euro.net>
NNTP-Posting-Host:	i450.asd.euronet.nl
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

I now have working code to install a TSR application that can be accessed by
a software interrupt handler (will mail the skeleton to the newsgroup when
finished).

The TSR code was downloaded from the mail archives and looks like this:

__go32_dpmi_registers r;
/* ............... */
r.x.ax = 0x3100;
r.x.dx = 1000;    // more than emough
__dpmi_int(0x21, &r);

Q1) How can I compute the correct value to be passed in the DX register?
Currently I am passing 1000 paragraphs because this is more than enough, but
how can I compute the exact number?

Q2) Now I want to implement a "quit" command, that will also reach the TSR
via the software interrupt handler. But how can my TSR terminate itself
gracefully? I have tried:

__go32_dpmi_registers r;
/* restore original interrupt handlers */
r.x.ax = 0x3100;
r.x.dx = 0;    // terminate
__dpmi_int(0x21, &r);

But after this code has been executed, the PC still runs, but it seems I get
a page fault on evry program that I try to run (including the DJGPP
compiler). This is not caused by improper interrupt restoring, because if I
leave my program in the regular way, everything is OK.

Any suggestions?

--
Jan Humme.

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