设计四个类；学生类（描述学生基本信息）；成绩类：班级类；课程类（描述课程信息：课程编号，科目名称（如高等数学，大学英语等）；-Design of the four categories　student class (described students basic information)　performance class: class class　course class (descr iption course information: course number, course name (such as mathematics, English, etc.)