Flag (ULONG) - input

Wait flag.
• IO_WAIT
  Wait for a keystroke if one is not available. The keystroke returned is removed from the queue.
  
• IO_NOWAIT
  Return immediately, with or without a keystroke. If a keystroke is returned, remove it from the queue.
  
• IO_PEEK
  Return immediately, with or without a keystroke. Do not remove the keystroke from the queue.
  
• IO_PEEKWAIT
  Wait for a keystroke if one is not available. Return the keystroke but do not remove it from the queue.