Unix filesystem

[2] As in other operating systems, the filesystem provides information storage and retrieval, and one of several forms of interprocess communication, in that the many small programs that traditionally form a Unix system can store information in files so that other programs can read them, although pipes complemented it in this role starting with the Third Edition.

Also, the filesystem provides access to other resources through so-called device files that are entry points to terminals, printers, and mice.

[1] The mathematical traits of hard links make the file system a limited type of directed acyclic graph, although the directories still form a tree, as they typically may not be hard-linked.

(As originally envisioned in 1969, the Unix file system would in fact be used as a general graph with hard links to directories providing navigation, instead of path names.

[3] Symlinks were modeled after a similar feature in Multics,[4] and differ from hard links in that they may span filesystems and that their existence is independent of the target object.