; yoinked from osdev.org
mov ax, 0x07C0
mov ds, ax

mov si, msg
cld

ch_loop:
  lodsb
  ; hang if at null terminator
  or al, al
  jz hang

  ; BIOS interrupt prints al
  mov ah, 0x0E
  mov bh, 0
  int 0x10

  jmp ch_loop

hang:
    jmp hang

msg db 'Hello World', 0

times 510-($-$$) db 0 ; 2 bytes less now
db 0x55
db 0xAA