Port(Connector &con, const char *name): This
constructor assigns the connector reference to the external
protected data member as described next and passes the name of the
port to the base Connector constructor. The constructor
of the Port class is protected so as to prevent actual
objects of the class from being instantiated; only classes
derived from Input and Output can be created.
Connector *external: This member represents the
external connector to which the port itself is connected. This data
member usually points to a port in an hierarchical level immediately
above the port or to a wire in the same hierarchical level as the port.
Note that because Wire and Port are both derived
from the Connector class, external may point to
either a Wire object or a Port object.