多线程的经典例子，这是上课老师的例子。具有学习意义-Classic example of multi-threaded, this is the class teacher s example. With learning the meaning of

可以求出多位数的阶层，可以通过修改代码中的值使程序的功能提升，求n的阶层，n！-Class multi-digit class can be obtained by modifying the value of the code to make program enhancements, and n, n!

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 "Ci