源程序：
//1.设计一个基类，从基类派生圆柱，设计成员函数输出它们的面积和体积；
#include < iostream >
using namespace std;
class Basic//基类
{
protected:
double r;
public:
Basic() { r = 0; }
Basic(double a) :r(a) {}
};
class Circular : public Basic//从基类派生圆类
{
protected:
double area;
public:
Circular(double a)
{
r = a;
area = area = 3.1415926 * r * r;
}
double getArea()//返回圆面积
{
return area;
}
};
class Column : public Circular//从圆类派生圆柱类
{
protected:
double h;
double cubage;
public:
Column(double a, double b) : Circular(a)
{
h = b;
cubage = getArea() * h;
}
double getCubage()//返回圆柱体积函数
{
return cubage;
}
};
void main()
{
Circular circular(45);
Column column(12, 10);
cout << "圆的面积：" << circular.getArea() << endl;
cout << "圆柱的体积：" << column.getCubage() << endl;
system("pause");
}
运行结果：