操作系统中的文件是通过文件目录项来管理的，为了管理和查找的方便，按层次把文件目录项组织起来，同一层上的目录构成该层上的目录，第一层为根目录，一下为各层子目录。 假设以一串字符代表一个文件，每个字符表示一个记录。 在建立上述目录结构的基础上，建立相应的管理系统并要求完成以下各项操作： 1．　　一次建立各个文件 2．　　查访两个用户的所有文件 3．　　查访用户sun 是否有文件AB 4．　　删除用户sun的文件AC,然后在分别查访两个用户的全部文件，检查是否已经删除文件AC 5．　　撤销用户sun,并检查是否被删除 6．　　删除用户sun的全部文件，然后在撤销sun用户，在查访用户sun, 检查其是否已被撤销。 在建立一个新用户及新用户的两个文件，然后查该两个用户的所有文件-operating system, the paper is to document catalog items to the management, in order to manage and facilitate the search, according to the document level directory entries organizations, the same floor on which constitute the directory contents on the floor, the first layer of the root directory to look for levels of subdirectories. Assuming that the representative of a string of characters, each character expressed a record. In establishing the directory structure on the basis of the establishment of a corresponding system of management and asked to accomplish the following : 1. Once established two separate files. Visits to the two users of all three documents. Sun user visits whether documents AB 4. Sun users to delete the documents AC, then two separate visits to all users of the docum