通过C++实现学生管理系统，主要功能包括：学生信息录入、学生成绩录入、学生信息修改、成绩信息修改、学生成绩情况查询（可计算学生GPA）-a system helping manage student s score, with the functions as follow: take in student s infomation, take in student s score, rewrite student s infomation or score, look up student