43/50 line text modes

[Dave Gillett]

In <7698 at umd5.umd.edu> wchan at umd5.umd.edu (Winthrop D Chan) writes:

>I need some help on this one. I am trying to figure out how most of these
>programs are able to put an EGA/VGA display into 43/50 lines of text on the
>display. I went thru the BIOS listings and none of them really show anything
>more than 80x25 text mode. Is it by somehow changing the character set?
>I nned to find out soon so I can finish my final project.

>I also need to find out how to address the display in that mode using
>direct screen writes. (ie. base address, display organization, etc....)


     You don't need a message, you need a book.  Specifically, you need
"The Programmer's Guide to IBM PC and PS/2 Video Systems" by Richard Wilton.

     First of all, the display memory organization for all of the common video
adapters is clearly explained there.
     Secondly, the interface by which software (yours or the BIOS') controls
the graphics hardware is clearly explained.  Each of the mode numbers defined
in the BIOS corresponds to some setting of various hardware parameters; since
IBM has not defined BIOS mode numbers for the 43/50-line modes, your software
must set those hardware parameters directly in order to use them.

     It should be pretty clear that a complete answer to your question would
consume massive amounts of bandwidth....
                                                        Dave