From mboxrd@z Thu Jan  1 00:00:00 1970
From: wkt@tuhs.org (Warren Toomey)
Date: Fri, 18 Mar 2016 10:48:32 +1000
Subject: [TUHS] Early non-Unix filesystems?
Message-ID: <20160318004832.GA18245@minnie.tuhs.org>

It's a bit off-topic, but what were non-Unix filesystems like around 1969-1970?
The PDP-7 filesystem has i-nodes (file metadata) and filenames separate
from the i-nodes. This allows hard links and thus a non-tree structured
filesystem.

This has always struck me to be one of the most important features of
the Unix filesystem: names separated from the rest of the file metadata,
and arbitrary hard links so that there is no preferred filename.

Were these features in other contemporaneous filesystems?

As a side note, the PDP-7 kernel knows about the top-level directory ("dd")
but it is agnostic to the concept of "." and "..". What that means is
that you can build a filesystem with "." and ".." links and the kernel
will deal with them as per all other links. But you can also build a
filesystem without "." or ".." and the kernel doesn't care.

There's not enough evidence (source code, papers, anecdotes) to confirm
or deny the presence of "." in the PDP-7 code that Norman scanned for us.
".." does seem to exist as it is mentioned in one source file, ds.s.
It's an intruiging mystery.

Cheers, Warren