[ORG 0x7c00]
mov ax, 0
mov ds, ax
jmp 0:start
start:

mov ax, 0x1000
mov es, ax
mov bx, 0

mov al, 0x20
mov dh, 0
mov ch, 0
mov cl, 0x2

mov ah, 0x2
int 0x13

jmp 0x1000:0

times 0x1fe-($-$$) db 0
db 0x55
db 0xaa