由于C语言中操作系统不是很方便，因此大部分的数据存储都是通过文件来进行的。数据存储采用3个文件来实现。程序第一次运行的时候便会自动在目录下创建。BOOK.DAK，用于保存图书信息；MEMBER。DAT，用于保存会员信息；TRANS。DAT，用于保存业务信息，即结束还书信息。-Since the C language in operating system is not very convenient, so most of the data storage are carried out through the document. Data storage used to achieve the three documents. Procedures when the first run will be automatically created in the directory. BOOK.DAK, for the preservation of book information　MEMBER. DAT, for the preservation of Member information　TRANS. DAT, for the preservation of business information, that is the end of book information.