jmp start

intfunc1:
   cli
   mov edi, 0xB8000
   mov esi, string
   mov ah, 0x0F
   .displaying:
   lodsb
   stosw
   or al, al
   jnz .displaying
   iret

string: db "Hello world!", 0


start:
mov ax , 0 ; move zero into ax
mov es , ax ; make es point to begining of IVT which is 0000:0000
mov eax , dword intfunc1 ; move interrupt function address into eax
mov dword [es:0400] , eax ; move eax into the 100th entry of the IVT
sti
int 64h ; call the 100th interrupt service routine

end:
jmp end

times 510-($-$$) db 0
dw 0AA55h ; some BIOSes require this signature