How to add 13.10 after reading string ?

Question

I’m trying to record a 40x20 character array, doing 2 cycles, where the character reads the character guard in a buffer, but I know we have to add 13.10 to change line and the cursor goes back to the beginning. But 13.10 is considered one byte? How can I add 13.10 at the end of the line or after reaching the last character of the line.

Part of the code

xor cx,cx
xor si,si
xor ax,ax

mov cx, 20
forLine: 
    forColumn:
        mov         ah, 08h ; Guarda o Caracter que est� na posi��o do Cursor
        mov     bh,0        ; numero da p�gina
        int     10h 
        mov caraterLido, ah     
        mov buffer[SI], caraterLido
        inc si
        cmp si, 40
        jne forColumn
        //quando for igual a 40, adicionar 13 e 10 no fim da linha 

loop forLine