先定义“点”类Point，由“点”类派生出“圆”类Circle，再由“圆”类生成“圆柱体”类cylinder。圆类的属性有圆心和半径（指针类型）；方法有构造函数、析构函数、显示面积和计算面积。圆柱体类的新增属性是高度，方法有构造函数、析构函数、显示体积和计算体积。类的应用：创建一个圆柱体类，显示信息，求它的体积。类的定义与实现及主函数以多文件组织。-The first definition of "point" Point, "points" class derived from the "Circular" class of Circle, then the "Circular" class generation "cylinder" cylinder. Attribute class circle center and radius (the pointer type constructor, destructor)　method, display area and calculate the area. New attribute cylinder is high, a constructor, destructor method, display size and volume calculation. The application of class: create a cylinder type, display information, and its volume. The class definition and implementation and main function to multi file organization.