[TUHS] Early non-Unix filesystems?

Warren Toomey wkt at tuhs.org
Fri Mar 18 10:48:32 AEST 2016

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

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

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