定义一个抽象类的CShape,包括纯虚数Area(用来计算面积）和SetData（用来重设形状大小）。然后派生出三角形CTriangle类、矩形CRect类、圆CCircle类，分别求其面积。最后定义一个CArea类，计算这几个形状的面积之和，各形状的数据通过CArea类构造函数或成员函数来设置。-Defines an abstract class CShape, including the pure imaginary number Area (used to calculate the area) and SetData (used to reset the shape, size). Then the triangle CTriangle derived class, rectangle CRect class, round CCircle categories, seeking its size. The final definition of a CArea class, calculate the size of the sum of several shapes, each shape data through CArea class constructor or member function to set up.