本段代码完成的功能有：学生成绩管理系统，菜单显示学生信息的查看、添加、删除、修改、计算平均成绩、保存、退出系统操作等功能，为用户提供友好的功能选择界面，用户通过键入数字或者字母实现功能选择，进入相应的功能。-Completion of the section of code: Student achievement management system, menu display student information to view, add, delete, modify, calculating the grade point average, save, exit the system operation function selection interface to provide users with a friendly user by typing The function select number or letter, the corresponding function.