用C语言编写程序，模拟二级目录的文件系统 建立一个模拟文件系统，能实现建立、打开、删除、关闭、复制、读、写、查询等功能-use C language write programmes,simulate two-level directory file systems,create a simulated file systems in order to realize the functions such as create,open,delete,close,copy,read,write,f