说明：  学生类的基础上派生出一个子类；定义一个矩形类，计算其面积，定义派生类计算正方形面积；利用继承关系，定义点类、矩形类、长方体类，并测试之；实现二进制与十进制的转换；11~999之间的回文数
(A subclass derived from the student class; Defines a rectangular class, calculates its area, defines the derived class to calculate the square area; Using the inheritance relation, define point class, rectangle class, cuboid class, and test it; Implementation of binary and decimal conversion; The number of palindromes between 11 and 999.)