&quot;On the Multicians site it suggests Multics had a very different concept of &quot;files&quot;, which could also be &quot;segments&quot;. There was apparently potential ambiguity regarding the term &quot;file&quot;.&quot;<p>Segments are a hardware mechanism often used then for accessing or protecting things in memory due to simplicity &amp; speed of mechanism. Several modern techniques in INFOSEC use segments to protect programs.<p>Here&#x27;s how the MULTICs filesystem worked, though. Gist of it seems like MULTICS came up with all the key concepts I recognize for hierarchical, filesystems.<p><a href="http:&#x2F;&#x2F;www.multicians.org&#x2F;fjcc4.html" rel="nofollow">http:&#x2F;&#x2F;www.multicians.org&#x2F;fjcc4.html</a><p>Hansen&#x27;s history shows the Titan System also had a similar filesystem:<p><a href="http:&#x2F;&#x2F;brinch-hansen.net&#x2F;papers&#x2F;2001b.pdf" rel="nofollow">http:&#x2F;&#x2F;brinch-hansen.net&#x2F;papers&#x2F;2001b.pdf</a><p>Both predate UNIX with Thompson and Ritchie actually using MULTIC before writing UNIX. So, it&#x27;s probably main influence.<p>&quot;Today we often see the phrase &quot;Everything is a file&quot; being cited when introducing people to UNIX. But I have never seen anyone attempt to explain why. What was the context in the 1970&#x27;s?&quot;<p>It&#x27;s explained here:<p><a href="https:&#x2F;&#x2F;superuser.com&#x2F;questions&#x2F;364152&#x2F;why-is-everything-is-a-file-unique-to-the-unix-operating-systems" rel="nofollow">https:&#x2F;&#x2F;superuser.com&#x2F;questions&#x2F;364152&#x2F;why-is-everything-is-...</a><p>More detail from authors (see 3.3):<p><a href="http:&#x2F;&#x2F;www.scs.stanford.edu&#x2F;nyu&#x2F;04fa&#x2F;sched&#x2F;readings&#x2F;unix.pdf" rel="nofollow">http:&#x2F;&#x2F;www.scs.stanford.edu&#x2F;nyu&#x2F;04fa&#x2F;sched&#x2F;readings&#x2F;unix.pdf</a><p>&quot;Again, this early manual says: &quot;The most important role for UNIX is to provide a file system.&quot;&quot;<p>Ritchie was clear in other writings that there wasn&#x27;t a single goal for UNIX at all other than to be usable and more than what they were working with. It was designed to be efficient and enable programmers rather than hold them back. The rest fell into place from there.