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denial



Joined: 12 Sep 2004
Posts: 98
denial
I think cmp has some problems with handling signed (negative) integers. What am I doing wrong? The following code is for DOS:

Code:
org 100h

mov ecx,-3
neg ecx
mov edx,5
cmp ecx,edx
ja @f
mov ah,2
mov dl,1
int 21h
@@:
int 20h    


If ecx is smaller than edx (-3 smaller than 5), the ASCII-Code 1 (a smiley Smile ) will be drawn. This works, because actually it GETS drawn Wink

But now, the with the following code, the smiley won't get drawn! I just changed -3 into -8.

Code:
org 100h

mov ecx,-8
neg ecx
mov edx,5
cmp ecx,edx
ja @f
mov ah,2
mov dl,1
int 21h
@@:
int 20h
    


So I think cmp cannot handle signed integers at all. Maybe the first code worked because even without the sign, 3 is still smaller than 5. But when the sign of -8 is taken away, 8 will be greater than 5.

So how to handle signed integervalues with cmp? Sad
Thank you...
Post 03 Feb 2005, 22:55
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Matrix



Joined: 04 Sep 2004
Posts: 1171
Location: Overflow
Matrix
use jump if less, and greater Smile
jL
jG
Post 03 Feb 2005, 23:35
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denial



Joined: 12 Sep 2004
Posts: 98
denial
oh... Embarassed
That was easy... ok... thank you. Rolling Eyes
Post 03 Feb 2005, 23:41
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Matrix



Joined: 04 Sep 2004
Posts: 1171
Location: Overflow
Matrix
you're welcome
Post 04 Feb 2005, 01:17
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