Path: utzoo!attcan!uunet!mcvax!hp4nl!dutrun!vlruo02
From: vlruo02@dutrun.UUCP (Ge van Geldorp)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Disk I/O in Resident MS-DOS Program
Keywords: TSR,Background Processing,MS-DOS Reentrancy
Message-ID: <656@dutrun.UUCP>
Date: 28 Feb 89 18:37:13 GMT
References: <1872@holos0.UUCP> <2506@sun.soe.clarkson.edu> <13211@steinmetz.ge.com>
Organization: Delft University of Technology, The Netherlands
Lines: 18

In article <13211@steinmetz.ge.com> dixon@sagittarius.steinmetz.ge.com (walt dixon) writes:
>... The
>int 21h dispatcher works with 3 stacks -- auxilliary,  user,  and disk.  A very
>limited number of requests (ah = 33h,50h,51h,62h) are serviced with no stack
>switch.  Other requests with ah > 0ch are  finally serviced on the disk stack.
>Requests corresponding to ah=1 to 0ch are serviced on the user stack. A request
>on the user stack can be preempted by an int 21h request ah > 0ch.

Question: when is the auxilliary stack used?

>PRINT.COM,  which should be regarded as a model TSR hooks int 25h and 26h as
>well as int 13h.

Are you sure about this? The 25h and 26h interrupt vectors remain
unchanged when I run PRINT.COM (using PC-DOS 3.30). 


Ge van Geldorp.