On 5/27/2015 11:35 AM, JAYDEN CHARBONNEAU wrote:
> Huh.I thought all screens had the same columns and rows (Different 
> scales,obviously),but the same text slots.Apparently CGA monitors are 
> different.
>
Not by a longshot... Just look at such simple things as 40x25 mode. And 
it is not an issue with the "monitor" but with the video adapter, that 
generates the display info...

Any CGA card will support 40x25 as well as 80x25. A Monochrome adapter 
(not Hercules!) will only support 80x25. Starting with the EGA, s 
standard 80x43 mode was added to the mix, VGA added 80x50. Those are 
standard modes. Beside that, "most" VGA adapters are also able to handle 
various different resolutions, including settings like 132x96.

Checking 0040:0084 for the screen height should work even for 
non-EGA/VGA adapters or the PC has a really bad BIOS. I don't have 
access to my FreeDOS/PC stuff right now, as I am currently "between 
apartments", to check, but I am certain that I have at least a couple of 
PCs with MDA cards (both 80286) that I am sure will have that memory 
location set properly.
But to be safe, the check should only made if a display mode >7 is used...

Ralf

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