Position of character in a string

;PROGRAM TO FIND THE POSITION OF A CHARACTER IN THE GIVEN STRING

data segment

source db 'abcdefg'

len equ $-source

postn db 0

data ends

code segment

assume cs:code,ds:data

start:

mov ax,data

mov ds,ax

mov es,ax

mov di,offset source

mov cl,len

cld

mov al,'d'

repne scasb

jnz ex

mov bx,di

mov postn,bl

ex:

int 3

code ends

end start