问汇编OS -如何在第二行上写入文本？

EN

start:
        mov ax, 07C0h
        add ax, 288
        mov ss, ax
        mov sp, 4096
        mov ax, 07C0h
        mov ds, ax

        mov ah, 09h
        mov cx, 1000h
        mov al, 20h
        mov bl, 17h
        int 10h
        mov si, text_string
        call print_string
        jmp $

        text_string db 'This is my Operating System!', 0
print_string:
        mov ah, 0Eh
.repeat:
        lodsb
        cmp al, 0
        je .done
        int 10h
        jmp .repeat
.done:
        ret
        times 510-($-$$) db 0
        dw 0xAA55