ASM code for using Addition in Arithmetic / Logical Instruction Set

.model small
.stack 100h
.data
message db "Enter a Number $"
message2 db "Enter 2nd Number $"
message3 db " +  $"
message4 db " = $"
.code
main proc
mov ax,seg message
mov ds,ax
mov dx,offset message
mov ah,9h
int 21h

mov ah, 1h ;store input in al
int 21h

mov bl,al

mov ax,seg message2
mov ds,ax
mov dx,offset message2
mov ah,9h
int 21h

mov ah, 1h ;store input in al
int 21h

mov cl,al

mov dl,bl
mov ah,2h
int 21h

mov ax,seg message3
mov ds,ax
mov dx,offset message3
mov ah,9h
int 21h

mov dl,cl
mov ah,2h
int 21h

mov ax,seg message4
mov ds,ax
mov dx,offset message4
mov ah,9h
int 21h

sub bl,30h  ;converts to decimal
sub cl,30h

add bl,cl
add bl,30h

mov dl,bl     ;prints character
mov ah,2h
int 21h

mov ah, 4ch
int 21h

endp
end main