Introduction - If you have any usage issues, please Google them yourself
Teaching Objective: To request the essence of understanding the meaning of inheritance and object-oriented technology in the importance of the statement to correct the relationship between the two types of inheritance understanding of polymorphism and the concept of virtual function to understand the abstract class function. Second, teaching focus: the achievement of inheritance, as well as the realization of polymorphism. Third, teaching difficult: virtual function (polymorphism) working principle, the concept of abstract class.