操作系统实验：模拟采用二级目录结构的磁盘文件系统中的文件操作。程序简单模拟了一个类unix的shell界面,并完成了实验中中所要求的具体内容。运行时需注意问题：初始用户名密码为root,登陆后可输入help命令查看命令格式获取帮助。 已通过测试。

-Operating system experiments: simulation using two disk file system directory structure, file operations. The program is simple to simulate a unix-like shell interface, and complete the specific requirements in the experiment. Runtime should pay attention to the problem: the initial user name password for root, after landing Enter the help command to view the command format for help. Has passed the test.