添加功能：添加数据信息，当有新同学进入是可以添加该同学的信息。
精确查询：输入要查询同学的学号，显示出该同学的信息。
删除功能：该功能和精确查询功能在同一功能模块中实现，用于删除同学信息。
修改功能：当同学的信息改变时，用此功能更新同学信息。(Add function: add the data information, when a new student enters is the information that can be added to the student.
Accurate inquiry: input to inquire the student's school number, show the student's information.
Delete function: this function and accurate query function are implemented in the same function module and used to delete students' information.
Modify the function: when the information of the students change, use this function to update the students' information.)