Converting lower to upper or vice verssa

; You may customize this and other start-up templates;
; The location of this template is c:\emu8086\inc\0_com_template.txt

org 100h

.data

MSG1 db "Enter a lowercase character = $"
MSG2 db 0dh,0ah, "In upper case it is = "
Char db ?, "$"

; add your code here

.code

mov ax, @data
mov ds,ax
lea dx, MSG1

mov ah,9
int 21h

mov ah,1
int 21h

sub al,20h
mov Char, al

lea dx, MSG2

mov ah,9
int 21h

ret