FileSystme

说明：  多用户多级目录的文件系统,（1）具有login (用户登录) （2）系统初始化（建文件卷、提供登录模块） （3）文件的创建： create （4）文件的打开：open （5）文件的读：read （6）文件的写：write （7）文件关闭：close （8）删除文件：delete （9）创建目录（建立子目录）：mkdir （10）改变当前目录：cd （11）列出文件目录：dir （12）退出：logout
(Multi-user multi-level directory of the file system, (1) has a login (user login) (2) system initialization (construction paper roll, providing registry module) (3) the creation of documents: create (4) file to open: open (5) paper read: read (6) to write the document: write (7) document Close: close (8) delete the file: delete (9) create a directory (the establishment of a subdirectory): mkdir (10) to change the current directory: cd (11) are listed in directory: dir (12) Exit: logout)