Sometime back before the turn of the century, I remember
writing up a summary of the evolution of the UNIX file
system, starting with the earliest system I could find
information for (possibly the PDP-7 system) and running
through the printed manuals as things changed, up to
the Seventh Edition.
I think I've found it; I'll look it over and try to put
it somewhere on the web in the next day or two.
Norman Wilson
Toronto ON