学生成绩管理系统：

需求描述：

学生成绩管理系统中：

1．　　系统用户

系统的用户是学校的学生和教师。教师使用本系统录入和查询自己所教课程的考试成绩。学生只能查询自己的成绩。

2．　　系统功能

(1)　　成绩录入：

教师可以查询自己本学期所授课程，并录入学生的考试成绩。录入完成后提交，保存成绩。某门课程的成绩提交后，只能查询不能再进行任何修改。

(2)　　成绩查询：

学生只允许查询自己的考试成绩。

教师只允许查询自己所授课程的成绩。

(3)　　成绩统计：

教学管理员根据学生成绩统计处于优、良、中、及格、不及格的学生人数以及占总人数的百分比。其中100-90为优，89-80为良，79-70为中，69-60为及格，60分以下为不及格。

按要求输出成绩在优、良、中、及格、不及格各区间的学生学号。

-Descr iption: The demand for student achievement management system: a. Users of the system user' s system is the school' s students and teachers. The teachers use the system to input and query the examination results of courses taught. The students can only check their own performances. Two. Results of system functions (1) entry: Teachers can check their semester taught courses, and entered into the students'　test scores. Submitted after the entry completed, save the results. After the submission of the results of a course, the only query can no longer be any changes. (2) result inquiry: the student is only allowed to inquire about his exam results. Teachers will only allow to check the results of the Course. (3) results statistics: teaching administrators based on student achievement statistics in excellent, good, pass the number of students, as well as the percentage of the total number of failed. 100-90 for excellent ,89-80 is good ,79-70 in ,69-60 for the pass 60 points to