c语言教程：结构体的运用。按键功能：1：输入学生信息 2：按平均成绩由高到低排序 3：按姓名由小到大排序 4：以学号查找学生信息 5：以名字查找学生信息 6：修改某学生信息 0：结束程序(C language course: the use of the structure. Key features: 1: input student information 2: according to the average scores from high to low sort by name: 3: 4 in order from small to large school to find student information 5: name lookup 6: modify the student information student information 0: the end of a program.)