From: gswan AT globalserve DOT net (George Swan)
Newsgroups: comp.os.msdos.programmer,comp.os.msdos.djgpp
Subject: Re: Interrupts reserved for BASIC
Date: 28 Sep 1999 13:22:01 -0400
Organization: Globalserve Communications Inc.
Message-ID: <7sqtfp$5dt@globalserve.net>
References: <7slrv7$4nv$1 AT solomon DOT cs DOT rose-hulman DOT edu> <7sn3ai$ffq AT globalserve DOT net>
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To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

After reading some of the other responses here I thought I would
add that I have always assumed that, since DOS isn't multi-tasking,
that any interrupt vector that contained a NULL pointer was available
for my program to use.

I use a function like this one to look for them.

unsigned FindUnusedVector(              /* Find an unused interrupt vector */
        unsigned start )                /* start looking here */
{
        unsigned lastvector = TooHighVector;
        unsigned count;

        for (count = start ; count < lastvector ; ++count) {

                if (getvect( count ) == NULL)

                        break;          /* found an unused vector! */
        }
        return count;
}