caesarean shift

proc caesar
    push ax
    push bx
    push cx
    push dx
    ;start of proc

    mov ah, 09h
    mov dl, offset keyQuery


    call inputstring ;call inputstring to get key

    ;new line
    mov dl, 0Ah
    mov ah, 02h
    int 21h

    mov bx, offset stringbuff + 2
    xor cx, cx
    mov cl, [stringbuff + 1]

    mov al, [bx]
    mov dh, [bx+1]
    sub al, 30h
    sub dh, 30h
    mul [ten]
    add dh, al
    xor ah, ah
    mov [bx], ah
    mov [bx+1], ah
    mov [caesarKey], dh
    sub [caesarinvertkey], dh
    ;now the key is in caesarKey, and stringbuff is cleared again

    call inputstring

    ;new line
    mov dl, 0Ah
    mov ah, 02h
    int 21h

    mov dh, [caesarinvertkey]
    add dh, [A]

    mov bx, offset stringbuff + 2
    xor cx, cx
    mov cl, [stringbuff + 1]

    caesarloop:
        mov dl, [bx]
        cmp [byte ptr bx], '$'
        je endofcaesar
        cmp [byte ptr bx], ' '
        je nextcaesar
        cmp [bx], dh
        jge overthekey
        add dl, [caesarKey]
        nextcaesar:
            mov ah, 02h
            int 21h
            inc bx
            loop caesarloop
            jmp endofcaesar
        overthekey:
            sub dl, [caesarinvertkey]
            jmp nextcaesar
    endofcaesar:
        ;end of proc
        pop dx
        pop cx
        pop bx
        pop ax
        ret
endp caesar