编写一个程序实现文件读写操作、排序、查找、删除等操作。要求：

a．将“a.txt”文件中将学生成绩记录按照总分的由高到低方式排列，并将结果输出到“b.txt”。

总分相同的情况下，按照数学成绩的由高到低排列。

b．输入一个学生姓名，查找并输出他/她的信息。若无，则提示“无此人”。

　　 c．输入一个学生学号，查找并删除文件中他/她的记录。若无，则提示“无此人”。

d．增加一个学生信息到记录中，并保持文件中学生记录仍然有序，不可重复。

-Write a program to implement file read and write operations, sorting, search, delete, and so on.

Requirements:

A. record　a.t xt file　student achievement according to the total score　high to low arrangement, and will output the result into　b.t xt.

Total score of the same case, according to the math scores　high to low arrangement.

B. a student s name, enter search and output of his/her information.If not, the prompt　without the person .

C. a student student number, enter search and delete file his/her record.If not, the prompt　without the person .

D. add a student information to the records, and keep the file for middle school students record orderly, still not repeatable.