assembly interrupt 10h

[punjabian263]

hello guys,
I am using int video interrupt 10h to display a string hello world, but problem is it runs infinit loop and
terminate with error message, cpu encountered an illegual operation... will close.
here is main proc

.model compact
.stack 100h
.data
msg    DB  'Hello World!', 0   ; null terminated string.
.code
main proc
mov ax,@data
mov ds,ax
mov bh,0
CALL   printstring
mov ah,4ch
int 20
main endp

 

[punjabian263]

code of procedure printstring

printstring     PROC
mov si,offset msg	;moves offset of string defined in .data
next_char:		;label
    CMP  [SI], 0    ; check for zero to stop
    JE   stop         ;
    MOV  AL, [SI]     ; next get ASCII char.
    MOV  AH, 0Eh      ; teletype function number.
    INT  10h          ; using interrupt to print a char in AL.
    inc si            ; advance index of string array.
    JMP  next_char    ; go back, and type another char.
stop:
RET                   ; return to caller.
printstring     ENDP