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From: cs106132@umbc5.umbc.edu (cs106132)
Newsgroups: comp.sys.ibm.pc.programmer
Subject: INT 2F, subfunc 13h
Message-ID: <1991May26.064558.13108@umbc3.umbc.edu>
Date: 26 May 91 06:45:58 GMT
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Organization: University of Maryland Baltimore County
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Originator: cs106132@umbc5.umbc.edu


   Hi,
I found out that Int 2F, subfunc 13h is used to set the Int 13h address
and get the original one from DOS.  If I get it right, DOS device driver
grabs the original ROM address and replaces it with its own handler.  But
there is a way to find it out using undocumented Int 2F, 13h.  Something
like this:
 
   DS:DX points to current handler to set
   AX = 13h
   Int 2F
   DS:DX now contains the original address
   store away DS:DX
   Int 2F again to set it back to what it was

Does anyone have an idea what this is all about?  Any pointers will be
appreciated.

Ted Lee