第四章 面向对象编程
Object-oriented Programming - 类，构造函数和析构函数，类的指针
Classes. Constructors and Destructors. Pointers to classes. - 操作符重载,this,静态成员
Overloading Operators. this. Static members - 类之间的关系
Relationships between classes: friend. Inheritance - 虚拟成员，抽象，多态
Virtual Members. Abstraction. Polymorphism