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Index > DOS > Problem with int 21 (write string)

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fafastrungen



Joined: 12 Aug 2006
Posts: 27
fafastrungen
Hello, I'm trying to print a message in the screen but I can't get it work, this is my code:

format MZ
use16

jmp main

msg: db 'Hello World!$'

main:
mov ah, 09h
lea dx, ptr msg
int 21h

; the exit fuction [4C+no error (00)]
mov ax, 4C00h
int 21h

I'm not sure if I passing correctly the string in DS:DX.

Thanks in advance.
Post 13 Aug 2006, 01:56
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 7751
Location: Kraków, Poland
Tomasz Grysztar
You set up the DX correctly (though more usual syntax is "lea dx,[msg]"), but you have not set the DS. In this case you don't define a dedicated segment for data, so DS should be the same as CS - try putting this immediately after "main" label:
Code:
push cs
pop ds    

It will set up DS=CS.
Post 13 Aug 2006, 02:18
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fafastrungen



Joined: 12 Aug 2006
Posts: 27
fafastrungen
Thank you very much Tomasz and yes, you right, DS=CS.
I've tried to dedicate a data segment using .DATA but I got an error, how can I do it ?
Post 13 Aug 2006, 02:58
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 7751
Location: Kraków, Poland
Tomasz Grysztar
See the MULTISEG example in the DOS package.
Post 13 Aug 2006, 08:36
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fafastrungen



Joined: 12 Aug 2006
Posts: 27
fafastrungen
Tomasz Grysztar wrote:
See the MULTISEG example in the DOS package.


Thanks again man.
Post 13 Aug 2006, 13:42
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2



Joined: 26 Sep 2006
Posts: 92
2
I don't really know much about this?

Why not do this?

Code:
use16
org 256

mov ah, 09h 
mov dx,msg
int 21h 

int 20h 
msg: db 'Hello World!$' 
    


Is there some strange reason for adding format MZ? I think you're
trying to make an EXE. When I assembled that original code,it gave
me problems. It seems making DOS COM files is easier and
they are smaller.
Post 12 Oct 2006, 07:50
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