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Reverse a string

July 30, 2006

; reverse string

mov ah,0ah
lea dx,parameter
int 21h

mov ah,02
mov dl,0ah
int 21h
mov dl,0dh
int 21h

; initialize

xor cx, cx             ; zero out cx
lea si, origstring    ; si = inputted string
mov cl, [actlen]     ; cl = length of inputted string
dec cl                   ; since string starts from 0 to cl-1
lea di, revstring     ; di = empty
add di, cx   

reverse:
        mov al, [si]  ; get character
        mov [di], al  ; copy to di at ‘cl-1′th position
        dec di   
        inc si
 
 cmp al, ‘$’           ; means end of string
 jne reverse

mov ah, 09
lea dx, revstring
int 21h

int 20h

parameter label byte
maxlen db 0FF
actlen db ?
origstring db 0FF dup(’$')

revstring db 0FF dup (’$')

Posted by phengpheng at 4:49 pm | permalink

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A Computer Science graduate who is a fanatic in assembly, java, and j2me programming. Developed BlueVoice system (Direct Voice Communication in Mobile Phones), this system allows mobile users to experience FREE VOICE CALLS

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