任务概述：设计一个简单的教务管理程序，能新增、查询、显示、修改和删除学生的各科成绩信息。程序要求： 1）能够从屏幕上根据提示读取一个学生的成绩信息并保存。学生的各科成绩数据用文件来存储，按学号排序存放。 2）记录修改：能选择修改学生的姓名、班级和各科成绩，学号不可修改。在修改或删除之前需要用户进一步确认，确认无误后再进行操作。 3）能够按学号或姓名查询学生的成绩并显示。 4）统计功能：可以统计全部学生的总成绩及班上的排名；统计各科的平均成绩和及格率。 5）要求有友好的信息提示功能，例如学号只能是10位数字，输入错误应提示重新输入；查询数据不存在时提示用户；新增、删除、修改数据后提示成功与否。

-Descr iption of tasks: design a simple educational administration program, can add, query, display, modify, and delete student information results in all the subjects. Application requirements: 1) can be read from the screen according to the prompt a student performance information and save. Student subjects data file is used to store, sort by student number stored. 2) record changes: can choose to modify the student s name, class and grade, student id cannot be modified. Before you modify, or delete users need further confirmation, after confirmed. 3) can the student id or name query student performance and display. 4) statistics: statistics can all student s total grade and rank in the class　Statistical average grades and pass in all subjects. 5) requires a friendly message function, such as student number is only 10 digits, input errors should be prompted to input　Query data does not exist when prompting the user　Add, delete, modify the data after indicates success.