A means of locating data items, usually files. A directory can be regarded as establishing a set of links between named data items and their locations in a direct-access storage device. In many systems the directories are highly structured; their organization reflects the relationships between various categories of file. For example, the directory may allow one user to have other subordinate users, and permit controlled access by these subordinate users to their own and others’ files.

A directory may contain the names of files and of other directories. For instance, if directory x contained directory y, which contained file z, then it would be necessary to include x, y, and z in any reference to the file. See also access path.