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Index > Main > distance between variables. In code, not memory.

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b1528932



Joined: 21 May 2010
Posts: 287
b1528932
Code:
_sector_0_start:

jmp far 0x07c0:_a
_a:
org 0
mov ah, 0
int 16h

mov ah, 0x0E
mov bl, 0
int 10h

jmp _a



db (510 - 64) - ($ - _sector_0_start) dup 0 
db 64 dup 0
dw 0xAA55

    


i want to know the real distance between 2 labels in my code, not in memory. Is it possible? I want to use org as i like, its related to memory.
Post 27 Feb 2011, 03:16
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ouadji



Joined: 24 Dec 2008
Posts: 1081
Location: Belgium
ouadji
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Post 27 Feb 2011, 09:33
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b1528932



Joined: 21 May 2010
Posts: 287
b1528932
but seriously, i want to pad my file. Should i use external program to do that or what.
Post 27 Feb 2011, 16:45
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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
no way, to know the distance between two labels... just think a little, labels are just values, then, the distance between two values... you can't find?

of course, ones you declare a new adress space with org directive, all labels before are relative to previous adress space.

then, if you do that:
Code:
org 100h
label1: rd 342354
org 100h
label2: rd 5435
org 100h
label 3: rd 3435
    

all three labels will have the same value, then, cannot extract any absolute distance between. because separate adress spaces means: not at the same place, and can't predict effective distance ones in memory... because can be loaderd in distincts zones...
Post 27 Feb 2011, 19:22
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b1528932



Joined: 21 May 2010
Posts: 287
b1528932
ok, so any idea how can i pad to the end of a sector without worrying about org positions?
Post 27 Feb 2011, 20:10
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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
easy, did you read some code from this board before to ask?

i think you should search in OS construction section.

i posted many of them and the technique is easy.

from FASM manual, $ refer to the current offset... and $$ refer to the origin of the current adress space.

then, to padd a sector, just org it with any value you want (7C00h is better) and then, do the simple:
free=510-($-$$)
padding rb free

did i answer your question? and better, did it help you to understand Smile
Post 27 Feb 2011, 21:38
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