Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!jarthur!jmerrill
From: jmerrill@jarthur.Claremont.EDU (Confusion Reigns)
Newsgroups: comp.sys.ibm.pc
Subject: Re: detection of 43/50/... line modes
Message-ID: <5534@jarthur.Claremont.EDU>
Date: 28 Mar 90 09:09:16 GMT
References: <58consult@physc1.byu.edu>
Organization: Harvey Mudd College, Claremont, CA 91711
Lines: 17

In article <58consult@physc1.byu.edu> consult@physc1.byu.edu writes:
>    Is there a standard way to detect the number of lines an EGA or VGA display
>adapter is currently using?  It seems to me that there should be an address in
>the ROM data area that contains this info... Anybody know where?  What about
>querying the ansi/nansi/(etc) driver?

Yes.  Check memory location 0040:0084; it contains the number of screen
lines minus 1 (a 25-line display is 18 hex, a 50-line display is 31 hex).

NOTE to users of DESQview 2.26:  When DESQview forces a program to remain in
50-line mode, it fails to set this byte properly.  I discovered this when
using MS-Kermit's Tek emulation; when I came out, the display would only
cover the top half of the screen.  As it turns out, Kermit sets 40:84 to 18
as it leaves Tek mode, and DESQview doesn't set it back.

--
Jason Merrill				jmerrill@jarthur.claremont.edu