COM_NUM()
 Gives the number of the highest available serial interface port

 Syntax

     COM_NUM() --> nMaxCom

 Returns

     COM_NUM() returns the number of the highest available serial interface
     port.

 Description

     This function returns the number of the serial interface port available.
     This is not to say that a return value of 3 necessarily means that ports
     1 through 3 are available; for example, COM2 could be missing.  Whether
     or not a serial port can actually be used can be tested using the
     COM_OPEN() or COM_INIT() functions.

 Examples

     Determine the number of ports:

        ? COM_NUM()                 // e.g. 4