ComInput()

         Extracts a value from the comunications buffer (input)

    Syntax:

         ComInput() -> nValue

    Description:

         Receives a value from the comunications buffer.

         ComInput() brings up to date the internal pointers to the reception
         buffer to point to the next value.

    Return:

         The ascii value of the received byte on the port or Nil if there's
         no available byte or the manager isn't active.

    Example:

         While .T.
           If ! ComInEmpt()
             nValue  := ComInput()
             cString += Chr( nValor )
           EndIf
         End