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Configuration of COM ports

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A COM port is a type of serial port that complies with the following additional requirements:

  • You access the COM port through an instance of the COM port device interface class. The GUID for this class is GUID_DEVINTERFACE_COMPORT, which is defined in Ntddser.h.

  • You operate the COM port by using the 16550 UART-compatible interface that is defined in Ntddser.h.

  • To ensure compatibility with most applications that access COM ports, you should assign a symbolic link name that uses the standard naming convention COM<n>, where <n> is the COM port number (for example, COM1). If you use a COM<n> name, you must obtain the COM port number <n> from the COM port database. COM port numbers should only be used with COM<n> names.

By default, the combined operation of the class installer for the Ports device setup class and the Serial function driver configure a device as a COM port.

For information about how the Ports class installer and Serial function driver create a COM port device interface for a COM port, see External naming of COM ports.