Loading seg register (MZ files)

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Oddity

Joined: 09 Nov 2009
Posts: 2

Oddity 09 Nov 2009, 08:06

Hi. I am trying to create a dos executable where DS will contain the information I define in the .data segment, but I can't figure out how to do this.

Code:

use16
format MZ

segment .data

  mychar:
    db 0x41


segment .code
entry .code:0000

  start:
    mov ax, .data 
    mov ds, ax 

    mov ax, 0x4C00
    int 0x21

This of course gives me "undefined symbol 'start.data'". I've tried other things like

Code:

mov ax, segment .data

Code:

mov ax, seg .data

but of course they give me errors as well. Can anyone help me?

09 Nov 2009, 08:06

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20299
Location: In your JS exploiting you and your system

revolution 09 Nov 2009, 08:17

try with a double dot for the label name

Code:

segment ..data 
...
mov ax,..data

or even just without a dot

Code:

segment my_data 
...
mov ax,my_data

09 Nov 2009, 08:17

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8351
Location: Kraków, Poland

Tomasz Grysztar 09 Nov 2009, 08:18

Labels preprended with dot are a local labels, so when you write ".data" after the "start:" label, it looks for the "start.data" label actually.
You can either make all labels here local (change "start" to ".start"), or use some non-local names for segments (recommended), like "_data" and "_code".

EDIT: yes, revolution's advice is a good one, too. Smile

09 Nov 2009, 08:18

Oddity

Joined: 09 Nov 2009
Posts: 2

Oddity 09 Nov 2009, 08:25

Thanks =)

09 Nov 2009, 08:25

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