采用二级目录实现的简单模拟文件管理系统。普通文件的目录项包括文件名，文件类型，文件长度，指向文件内容的指针内容。目录文件的目录项包括目录名，指向下一级目录块的指针内容。-using two simple directory achieve simulation document management system. Ordinary paper catalog items including file name, file type, file size, the contents of the documents at the content of the target. Contents of the document catalogs items including the name of the directory, a directory at the next block as the target.