Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!urth!rfm
From: rfm%urth@Sun.COM (Richard McAllister)
Newsgroups: comp.sys.ibm.pc
Subject: Re: INT 28H
Message-ID: <45570@sun.uucp>
Date: 15 Mar 88 18:07:56 GMT
References: <3899@cup.portal.com>
Sender: news@sun.uucp
Reply-To: rfm@sun.UUCP (Richard McAllister)
Organization: Sun Microsystems, Mountain View
Lines: 14
Summary: Doesn't do anything, it's a hook for you

In article <3899@cup.portal.com> src@cup.portal.com writes:

>... when DOS is waiting for a keystroke, it makes frequent calls to
>interrupt 28h.  Unfortunately, there is no explanation of what INT 28h
>does.  Ray Duncan's "Advanced MS-DOS" book classifies INT 28h as one of the
>"Reserved" interrupts.  Can someone please shed some light on INT 28H for
>me?  Thanks.

According to the MS-DOS Encyclopedia, INT 28h as supplied does nothing (it's
just an IRET.)  It's there for TSRs to rip off if they want to steal some
cycles during idle times.  (I've heard that the PC-DOS PRINT spooler works
this way.)  

Rich