实现功能：

1.根据学号查询 学生的姓名 年龄 班级 年级等等

2.根据学号查询学生的成绩信息如数学 英语 语文

3.查询成绩名次及状况

4.收发信件

a.根据学号查找是否有信

b.删除已取走的信件

c.插入已知信件

使用说明:

1.把data文件夹的所有txt文件拷到c盘根目录下

2.直接运行源文件中的exe文件-The realization of functions: 1. In accordance with its inquiries, the students learn the names of the age grade, etc. Class 2. In accordance with its inquiries school information such as scores of pupils in mathematics in English language 3. Query results ranking and 4. Transceiver in accordance with the letter a. Are there places to find its b. the letter has been taken to delete the letter c. Insert known letters for use: 1. the data folder of all the txt files under the root directory c Kaodao 2. directly in the source file to run exe files