关于用多态定义一个车（vehicle）基类，有Run、Stop等成员函数，由此派生出自行车（bicycle）类、汽车（motorcar）类，从bicycle和motorcar派生出摩托车（motorcycle）类，它们都有Run、Stop等成员函数.观察虚函数的作用。-Definition of a vehicle (vehicle) base class member functions such as Run, Stop and derives bike (bicycle), automotive (motorcar) class, derived from the bicycle and motorcar motorcycle (motorcycle) class, they have a Run , Stop member function virtual function was observed.