登陆界面，学生管理，院系管理，课程管理，班级管理，成绩统计，用户管理，记事本，计算器，退出系统-Landing interface, the student management, college management, curriculum management, the class management and achievements statistics, user management, notepad, calculator, exit system

a big number class and a calculator using the cla-a big number class and a calculator using the class