problem with looping

[bigbeebrian]

the following code snippet copies from one place to another but doesn't want to decrement cx . An infinite loop has been created. can anyone tell me why and how I can fix it.
thanks




.MODEL SMALL
.386

.STACK 1024


.DATA

Message DB 'Press Any Key$'
videoSeg = 0B800h
scrnStorage = (25*80*2)
buffer DB scrnStorage dup(?)

.CODE

main PROC


mov si,videoSeg ;set DS to video segment
mov ds,si
mov si, 0 ; use as index

mov di,seg buffer ;set ES to buffer
mov es,di
mov di,offset buffer ; use as index
mov cx,scrnStorage ;counter

mov dl,[si] ;move video contents into buffer
mov es:[di],dl
inc si ;move thru video memory
inc di ;move thru buffer memory
dec cx ;decrement counter
cmp cx,0
jz spot


spot:

 

[Wody]

Hello,

the only strange thing that I see is that you jump to spot, even though it arrives there anyway, so at spot, this code will have only have run once.
You probably mean something like:

main PROC
mov si,videoSeg ;set DS to video segment
mov ds,si
mov si, 0 ; use as index
mov di,seg buffer ;set ES to buffer
mov es,di
mov di,offset buffer ; use as index
mov cx,scrnStorage ;counter
rep stosw
spot:
Wouter Dijkslag

http://www.wody.demon.nl

 

[bethae3]

I'm not sure you can use the string to loop through as the counter, I think you might actually have to set the counter to the size of the string?

 

[bethae3]

Sorry, I misspoke. Try setting the counter to the size of the string, plus one.

 

[bigbeebrian]

from:bigbeebrian

Thanks for all your help I think Ive got it now.