Need help getting a character from video memory...

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Steve

Joined: 10 Sep 2005
Posts: 10

Steve 09 Apr 2006, 23:20

Hi. Yesterday, with a lot of help from Spook, I was able to get this:

Code:

org 100h
use16

Main:

mov ah, 09h
mov dx, textOne

int 21h

mov bx,0x0B800
mov es,bx
xor di,di

mov al,BYTE[es:di]
mov BYTE[textTwo+9],al

;cmp al, 'l'

;je PrintSuccess

;int 20h

;PrintSuccess:

xor dx,dx
xor ax,ax

mov ah, 09h
mov dx, textTwo

int 21h

int 20h

Var:

textOne db 'Hello',13,10,'$'
textTwo db 'Returns:  $'

It's supposed to get the first character printed on screen from video memory. (Which is 'H') But, instead, it doesn't return anything. I really have no clue about segments so I'm looking for assistance to see how it should work. Any information / help on what's wrong would be great! Smile

Thank you,

- Steve

09 Apr 2006, 23:20

Dex4u

Joined: 08 Feb 2005
Posts: 1601
Location: web

Dex4u 09 Apr 2006, 23:53

So near, but so far Wink

, this code, does what you want on my PC.

Code:

org 100huse16Main:mov ah,09hmov dx,textOneint 21hmov bx,0x0B800mov es,bxxor di,dimov al,BYTE[es:di]mov BYTE[textTwo+9],al;cmp al, 'l';je PrintSuccess;int 20h;PrintSuccess:xor dx,dxxor ax,axmov ah,09hmov dx,textTwoint 21hxor ax,axint 16hint 20h Var: textOne db 'Hello',13,10,'$'textTwo db 'Returns:  ', '$'

09 Apr 2006, 23:53

Steve

Joined: 10 Sep 2005
Posts: 10

Steve 10 Apr 2006, 03:16

Hi, Dex. Wow, such bad luck! Sad

It seems I have been left out. Mad

This code doesn't work for me, either. Spook's code worked on his machine and yours worked on your own.. but they both don't work on mine. Terrible... :\

- Steve

10 Apr 2006, 03:16

TDCNL

Joined: 25 Jan 2006
Posts: 56

TDCNL 10 Apr 2006, 07:00

I've tested this piece of code too, (from you both) and it doesn't work on my PC either (WinXP SP2 Pro).

_________________
:: The Dutch Cracker ::

10 Apr 2006, 07:00

Dex4u

Joined: 08 Feb 2005
Posts: 1601
Location: web

Dex4u 10 Apr 2006, 11:23

Works on 5 win98, but not on xp, if yours is xp PC, then it does not seem to work on XP.

EDIT: I do not program on XP at all, but on some test i have just Carried out, it seems you can not directly access screen in XP.
Eg: this works fine in win98

Code:

org 100huse16Main:mov ax,0xB800mov es,axlea si,[textOne]mov di,2mov cx,10cldrep movsbxor ax,axint 16hint 20htextOne db 'H e l l o '

But not in XP Sad

.
screenshot:

Description:
Filesize:	14.09 KB
Viewed:	4775 Time(s)

10 Apr 2006, 11:23

Steve

Joined: 10 Sep 2005
Posts: 10

Steve 10 Apr 2006, 16:02

What a shame.. Mad

Oh well, thanks for helping me find out what was wrong. Very Happy

10 Apr 2006, 16:02

Dex4u

Joined: 08 Feb 2005
Posts: 1601
Location: web

Dex4u 10 Apr 2006, 19:01

Theres always DOSBox, runs great even on XP Wink

.
http://dosbox.sourceforge.net/news.php?show_news=1

10 Apr 2006, 19:01

Matrix

Joined: 04 Sep 2004
Posts: 1166
Location: Overflow

Matrix 10 Apr 2006, 21:08

Code:


mov ax,$0003
int 10h

put this at the beginning, and try on XP Wink

10 Apr 2006, 21:08

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