How do i write this assemly lang.program so that it can double any number passed to it :     ;DOUBLE This program prompt the user to enter 
    ;a number <5,
    ;doubles the number, and outputs the result
    	name	double
    	.model	small
    	.stack
    	.data
    prompt db oah,odh,"Enter a number <5:$"
    msg db Oah,Odh,"Double your number is :"
    result db?,Oah,Odh,"$"
    	.code
    start:
    		mov ax,@data
    		move ds,ax
    		lea dx,prompt
    	mov ah,9;dos fnto outputstring up to $
    int 21h
    mov ab,1;dos fn toinput byte into al
    int 21h
    sub al,30h;Convert from ascii to integer
    add al,al
    add al,30h;Convert back to ascii
    mov result,al
    lea dx,msg
    mov ah,9
    int 21h
    mo ax,4c00h;4c in ah is dos exit
    int 21h
    end start