---

#define START_OF_DISPLAY (short*)0xB8000
#define END_OF_DISPLAY (short*)0xB8FA0

void shift_screen(){
  memcpy(START_OF_DISPLAY, START_OF_DISPLAY + 80, 80 * 24 * 2);
  memset(END_OF_DISPLAY - 80, 0, 80 * 2);
}