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From: CMH117@PSUVM.BITNET (Charles Hannum)
Newsgroups: alt.msdos.programmer,comp.sys.ibm.pc
Subject: Re: i/o routines and non-standard video modes
Message-ID: <89338.051609CMH117@PSUVM.BITNET>
Date: 4 Dec 89 10:16:09 GMT
References: <2090@calvin.EE.CORNELL.EDU> <2980@einstein.ptolemy.arc.nasa.gov>
 <2092@calvin.EE.CORNELL.EDU> <2544@alva.tut.fi> <89320 <1494@cc.helsinki.fi>
Organization: Penn State University
Lines: 27

In article <1494@cc.helsinki.fi>, TEITTINEN@cc.helsinki.fi (Marko) says:
>
>In article <89320.130954CMH117@PSUVM.BITNET>, CMH117@PSUVM.BITNET (Charles
>Hannum) writes:
>> DOS (not necessarily BIOS) is hard-coded
>> to work with only the first 25 lines of the screen.  The problem here is that
>> to do anything else, DOS would have to automagically sense the current screen
>> size, which, since it uses BIOS calls, would tremendously slow down screen
>> I/O.
>
>I don't think screen handling is terribly slow in DOS 4.0, but it knows
>whether the screen is in 80*25 or 80*50 line mode. Easy to use (command
>is "mode ,50", but too few programs check whether they are running on
>80*25 or 80*50 line screen. Of course, all DOS programs do it,
>especially more.

You are naive.  DOS only *thinks* it knows what size the screen is.  In
reality, if you set the screen size without using MODE, DOS won't know a
damned thing about it.  How about using "MODE ,50" and having a program set
the screen back to 25 line mode.  What will DOS do?  Heh, heh ...
-------

--
- Charles Martin Hannum II       "Klein bottle for sale ... inquire within."
    (That's Charles to you!)     "To life immortal!"
  cmh117@psuvm.{bitnet,psu.edu}  "No noozzzz izzz netzzzsnoozzzzz..."
  c9h@psuecl.{bitnet,psu.edu}    "Mem'ry, all alone in the moonlight ..."