借书还书功能。不同读者类型的借书限制册和还书日期等约束条件的实现，还要有超期图书罚款处理功能。系统维护：如数据的备份等。图书查询：图书浏览。 -Borrowing and returning books feature. Limitations of different types of readers in library books and book the date of implementation of such cons