HELLO
IS ANYBODY KNOW WHAT THE ADDRESS OF THE RAM GENERATOR IN PC COMPUTER ?
HOW CAN I MODIFY IT FOR A NEW CHARACTERS ?
WITH GRATITUDE
Gabriel Tweto
Posted on 2011-09-18 05:38:32 by GabrielTweto

HELLO
IS ANYBODY KNOW WHAT THE ADDRESS OF THE RAM GENERATOR IN PC COMPUTER ?
HOW CAN I MODIFY IT FOR A NEW CHARACTERS ?
WITH GRATITUDE
Gabriel Tweto


Gabriel, in order to get help you will need to clarify your post.

i assume you are talking about VRAM ?

also please don't type in all caps.
Posted on 2011-09-18 14:16:06 by paradox

sorry :)
well I'm talking about the Ram Charcter Generator RCG in the pc computer
IBM wort these addresses in location 0007Ch - 0007Fh ( Address pointers ), which on my system contain the data 21h,96h,00h,C0h
calculating the address information gives the address C9621h
when I checked out I found the ASCII code from 127 through 255 in these addresses
I tried to change them to other characters of my own and my system freeze out, I mean stuck in an endless loop
These probably are not written abel address
These addresses should contain RAM array consisting of eight blocks of eight addresses Each
tha data in thes blocks defines the shape of the ASCII characters
I am discouraged with attempts Search
can you help me
Posted on 2011-09-21 16:04:05 by GabrielTweto
Hi Gabriel,
I thought that might be what you were looking for, but the reference to "RAM" confused me. I think you'll find that those addresses are in ROM, not RAM. You might find other "interesting" addresses by doing int 10h, ax=1130h (address returned in es:bp). Attempting to write to ROM wouldn't work, but "shouldn't" cause a hang (I don't think). Can you show the code that causes your computer to freeze?

If you're finding character generator data for 127 - 255 (128-255?), look a little lower... In order to alter  this data, you may need to copy it to a buffer in RAM, and alter it there. Then you'll need to tell video BIOS where to find it. Look around int 10h, ax=11xxh. (if you haven't got Ralf Brown's Interrupt List, find it!)

I vaguely recall having some code that would do similar things, but can't find it at the moment. I'll look more, now that I know that's what you want...

Best,
Frank

Posted on 2011-09-21 16:34:50 by fbkotler

Before anything else tank you for you'r effort and consideration
You gave me a heavy homework
I need time to digest this
Give me 24 hours
With great appreciation
Gabriel Tweto
Posted on 2011-09-21 17:06:14 by GabrielTweto
http://www.frontiernet.net/~fys/font.htm
Posted on 2011-09-22 07:49:06 by GabrielTweto
Yeah! Ben Lunt's "Forever Young Software" is an excellent source of information on dos-ish (and other) stuff! Ben's a real helpful guy! I don't know why I don't think of it more often. Thanks for the reminder!

Does that give you enough information to do what you need to do?

Best,
Frank

Posted on 2011-09-22 14:23:55 by fbkotler

I'm doing research about this INT routine
I wonder
If it were possible to establish reliable online software factory
With employees from all over the world
that each workers will make parts of  an large and very massive software
in assembly code which is fast accurate and take a small software volume
This industry can create the most profitable large projects
Maybe great then Microsoft
A thought flashed through my mind  :roll:

Gabriel tweto
Posted on 2011-09-22 17:30:57 by GabrielTweto
Attachments:
Posted on 2011-09-23 01:22:08 by GabrielTweto
I'll try it if I find myself in dos sometime soon. :)

I notice it doesn't include anything to test it with. How do you determine that it's not working? If it's not, it is quite possible that differences in video cards would account for it. Some of the cards with good hi-res modes may not emulate VGA 100% accurately.

I found an example from the legendary Beth Stone. As you'll see, she's quite verbose! I "translated" her work to Nasm syntax - shouldn't be too hard to "translate" it back to Masm/Tasm/Jwasm syntax, I mostly just commented stuff out. Yell if you have trouble. Notice I've got one of the int 10h's commented out. I don't recall if that caused trouble, or if I just wanted to see what would happen without it. You can try it both ways, if you care to.

Best,
Frank

Attachments:
Posted on 2011-09-23 02:39:19 by fbkotler

I have performed research in to the INT 10H software
and i encountered incomprehensible Assembly commands
Are you familiar with These commands ?
i attached Screenshot
Wish you best
Sincerely
Gabriel
Posted on 2011-09-24 18:18:43 by GabrielTweto
I'm not seeing your screenshot, Gabriel. Try again, or "spell 'em out". There is, no doubt, an explanation.

Best,
Frank

Posted on 2011-09-24 21:46:03 by fbkotler
There is a problem, i can not sent attached Screenshot files
I improvise as close as possible
I Used the DEBUG program
what is the CS: code mean ?

0000:297D 2E                CS:
0000:297E 803EBB0802  CMP BYTE PTR [08BB],02
0000:2983 7505            JNZ 298A
0000:2985 E852FF          CALL 28DA
0000:2988 725F            JB 29A9
0000:298A 2E                CS:
0000:298B 803EBB0801  CMP BYTE PTR [08BB],02
Posted on 2011-09-25 00:16:30 by GabrielTweto
The CS are operand prefixes which tell your code to look in the code segment for the information you are referencing. It basically translates into:

CMP BYTE PTR ,02
JNZ 298AH
CALL 28DAH
JB 29A9H
CMP BYTE PTR ,02

Posted on 2011-09-26 21:09:28 by Synfire
If no prefix, reads and writes use ds (with some exceptions). The above, without the prefixes, would mean:

CMP BYTE PTR ,02
JNZ 298AH
CALL 28DAH
JB 29A9H
CMP BYTE PTR ,02

You usually don't see prefixes in a code, because the convention is to not explicitly write a prefix if it is the default one.
Posted on 2011-10-09 07:55:33 by ti_mo_n