Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!bellcore!texbell!merch!cpe!hal6000!trsvax!don
From: don@trsvax.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Re: Help with sharing memory in DOS...
Message-ID: <216100107@trsvax>
Date: 13 Jul 89 13:28:00 GMT
References: <2752@blake.acs.washington.edu>
Lines: 34
Nf-ID: #R:blake.acs.washington.edu:2752:trsvax:216100107:000:1679
Nf-From: trsvax.UUCP!don    Jul 13 08:28:00 1989



> How do I find the address of 'aldsdata' inside the TSR??

> I'm guessing something like store the address of aldsdata in an interrupt
> vector, then declare a far pointer and put the address of aldsdata in that...
> But it ain't worked yet.

That's one way to do it, but that has problems.  For one, if some other program 
calls that interrupt, then you would almost assuredly lock up the machine.

Instead, a more general way is to take over some typically unused interrupt 
with an ISR (interrupt service routine).  The ISR would compare values passed
in AX with a table of commands you support.  For now, you could use AX=0
as a request for the address of aldsdata.  Since the ISR is part of your TSR,
it knows the address of aldsdata and can pass it back to the calling program
in some registers, such as ES:BX.  Your ISR can "chain" into the interrupt
vector, so that if some other program also uses that interrupt, their ISR
will also be called.  In order to use this ISR from another program, merely
call the interrupt with AX having 0, and get the address from ES:BX.

If you need more specific info, let me know.  I don't like to send code
fragments unless specifically requested to do so.  You also said you had
written the TSR, so you probably know more about the PC than you give
yourself credit.
---------------------------------------------------------------------
Computers are just the opposite of people.  With computers, you put
the software in the hardware, while with people, you put the hardware
in the software.

Don Subt			The opinions expressed above are
Tandy Corp.			strictly mine, not my employer's.

817-390-3068			...!killer!ninja!sys1!trsvax!don