数据管理功能: 1. 增加一个学生的纪录 2. 根据学号查看某个学生的成绩 3. 计算并输出每个学生的平均成绩 4. 计算并输出每门课的平均成绩 5. 计算并输出所有学生所有课程的平均成绩 6. 按平均成绩顺序输出学生名单 7. 学生退学删除该学生的纪录-data management functions : 1. An increase in the records of two students. According to a study, to see the results of the students three. Calculated and output of each student's average score four. Calculated and output per class average score five. Calculated and output of all students in all courses average score 6. average scores on the order list of seven students output. students who delete records of the students