Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!sri-unix!sri-spam!rutgers!uwvax!oddjob!gargoyle!ihnp4!homxb!homxc!djs
From: djs@homxc.UUCP (D.SPATHIS)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Screen Base Address
Message-ID: <1664@homxc.UUCP>
Date: Mon, 12-Oct-87 08:28:30 EDT
Article-I.D.: homxc.1664
Posted: Mon Oct 12 08:28:30 1987
Date-Received: Tue, 13-Oct-87 06:36:22 EDT
References: <5326@jhunix.UUCP> <2789@bnrmtv.UUCP>
Organization: AT&T Bell Laboratories, Holmdel
Lines: 27
Keywords: DOS Video address
Summary: Finding PC screen buffer address - some thoughts

In article <2789@bnrmtv.UUCP>, perkins@bnrmtv.UUCP (Henry Perkins) writes:
> In article <5326@jhunix.UUCP>, ins_agwa@jhunix.UUCP (Gunther Wil Anderson) writes:
> > Does anyone know how to determine the screen base address from
> > within DOS, independent of screen type (i.e. not by determining
> > the screen type and then assuming that the base address is what
> > it should be for that type)?
> 
> The screen base address isn't dependent on DOS; it's dependent on
> the display board you're using, and the BIOS which supports it.
  . . . . .  
> {hplabs,amdahl,ames}!bnrmtv!perkins         --Henry Perkins


One thought for finding the screen address goes something like this:

IF one possible place for the screen buffer is B000:1000 then read this
absolute memory location saving the data byte that is there.  Now write
some other non-blank value there.  Call a BIOS clear screen function.
Lastly, check the location again - if blank it's part of the active
screen buffer.  Repeat with more gueses for screen address until happy.

-Dennis
...ihnp4!homxc!djs


PS. don't forget to re-write the data back into memory!