The communications driver exports the CommWriteString and EnableNotification functions. The CommWriteString function writes a string of one or more bytes to the given communications device. The function improves performance by eliminating the series of individual calls to the sndcom function found in earlier versions of Windows.
The EnableNotification function enables or disables port status notifications. If notifications are enabled, the communications driver posts WM_COMMNOTIFY messages to a given window at the occurrence of certain events. This eliminates the need for communications applications to set timers and use the GetCommError, GetCommEventMask, and SetCommEventMask functions to watch for port status changes. This can result in system-wide performance improvements since the communications application no longer needs to service connections that may be inactive or take exclusive use of a system timer.