data segment 
	msg1 db 'Please input the String:','$'
	crlf db 13,10,'$'
data ends
code segment
	main proc far
	assume cs:code,ds:data
start:
    push ds
    sub ax,ax
    push ax
    
    mov ax,data
    mov ds,ax
    
    mov ah,09
    lea dx,msg1
    int 21h
    
    mov ah,09
    lea dx,crlf
   
    int 21h
    mov cx,20
again:
    mov ah,7
    int 21h
    cmp al,0dh
    jz exit
    
    xor al,0ffh
    mov dl,al
    
    mov ah,02
    int 21h
    loop again
exit:
    ret
    main endp 
   code ends
   end start