说明：  一个小型图书管理系统。用链表存储图书记录内容。能实现图书记录的添加，删除，查询，排序，修改，保存到文件和从文件中读取等功能。
(a small library management system. Chain store with the contents record books. Achieve the record books to add, delete, query, sort, modify, and the preservation of the document from the document read, and other functions.)