First code

.model small
.data

A db ?
B db ?



.code
main proc
    mov ah,1
    int 21h

    mov A, al
    int 21h

    mov B, al
    mov bh, A
    sub bh, B
    add bh,48


    Mov ah, 2

    mov dl, 0ah ;new line
    int 21h

    mov dl, 0dh ;remove space
    int 21h

    mov dl, bh
    int 21h

    mov ah, 4ch
    int 21h
    main endp
end main