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View Full Version : CGAtools, some tools to work with the CGA fontset.



xzakox
August 11th, 2010, 02:05 AM
Hey, I just uploaded a couple of very simple programs I did for working with the CGA character set.
One of the programs takes a binary image of the charset ROM of the CGA and creates a TXT file with a representation of the charset in "ascii-art" so you can see the characters and easily modify them.
The other one, takes this text file, and re-creates a binary image so you can burn it in an EPROM and replace your character ROM in the CGA card.

I made a quick test with mine, modifying the capital O and T, and here is the result:
http://a.imageshack.us/img708/9691/p1100572.th.jpg (http://img708.imageshack.us/i/p1100572.jpg/)

So, I thought somebody could want to play with this, and uploaded the files to github:
http://github.com/ladecadence/CGAtools

See the included README for more info.
Enjoy!
:)

per
August 11th, 2010, 02:24 AM
I usually prefere YY-CHR when doing things like this. However, YY-CHR will only work on Windows, while the source code you have posted should work on almost everything depending on how it is compiled.

xzakox
August 11th, 2010, 08:55 AM
Yes, I just made some changes so it compiles and works perfect on DOS, with TurboC installed.

:)

xzakox
August 11th, 2010, 02:30 PM
And here some font goodness, ripped from an arcade game, now in my CGA:
http://a.imageshack.us/img38/6222/p1100581.th.jpg (http://img38.imageshack.us/i/p1100581.jpg/)

EddieDX4
August 11th, 2010, 02:46 PM
And here some font goodness, ripped from an arcade game, now in my CGA:
http://a.imageshack.us/img38/6222/p1100581.th.jpg (http://img38.imageshack.us/i/p1100581.jpg/)

This is really cool! Is there a way to create a TSR based ROM patch, if we don't have the means to burn this into an EPROM?

southbird
August 11th, 2010, 02:48 PM
Isn't the original IBM CGA's character set in ROM?

xzakox
August 11th, 2010, 10:50 PM
This is really cool! Is there a way to create a TSR based ROM patch, if we don't have the means to burn this into an EPROM?

That's the problem, the CGA character memory isn't mapped in the PC memory map, is just accesible by the card, so you can't change it by software like on the EGA/VGA.

per
August 12th, 2010, 01:26 AM
That's the problem, the CGA character memory isn't mapped in the PC memory map, is just accesible by the card, so you can't change it by software like on the EGA/VGA.

We had a solution to that some time ago, by using graphics mode to emulate alphanumeric mode. In graphics mode, the upper half of the characterset is stored in RAM, pointed to by an Interrupt vector, something we could use to set costom fonts.

xzakox
August 12th, 2010, 01:30 AM
Yeah, sure, you can in graphics mode, it has been done by games and the like for ages, but not on text mode.