unix precursors

Eric Fischer enf at pobox.com
Thu Jun 8 08:50:45 AEST 2000

> Thompson mentions that unix borrows heavily from CTSS.  I think that
> Corbato wrote a book on this system, but that book seems nearly as
> rare as chicken teeth.  I think he also wrote an earlier journal
> article on the system, which I imagine shouldn't be hard to locate.

The journal article you're thinking of is probably "An Experimental
Time Sharing System" by Corbato, Merwin-Daggett, and Daley, which
describes an early version of the system (where command arguments
were still separated by vertical bars instead of spaces).  AFIPS
Conference Proceedings vol. 21, 1962.

The book is _The Compatible Time-Sharing System: A User's Guide_,
which was published in two editions in, I think, 1963 and 1965,
by MIT Press.  Both editions are in enough libraries you should
be able to get them by interlibrary loan.  The first edition is
more booklike, the second is more like a collection of man pages.

The Charles Babbage Institute has copies of some of the on-line
updates to the manual (on paper) from after the second edition
was published.

You will see many similarities to Unix.  The arguments to tar,
for instance, come straight from the CTSS "ARCHIV" command.

> Finally, Thompson also mentions that fork() basically existed in its
> current form in the Berkeley Timesharing System.  That is the one and
> only thing I have ever heard about this system.  Anyone know where I
> can learn more?

You can find out some things about it from Butler Lampson's "A User
Machine in a Time-Sharing System," at


Dennis Ritchie cites a real manual for the system in the references for


but I haven't been able to locate a copy, even in the library at
the University of California, Berkeley.  I've read somewhere that
the system is supposed to be similar to the PDP-1 time sharing
system developed at MIT, but the only documentation I've located
on that is Mario Bonghi's master's thesis, which seems to have been
written before the hardware was even upgraded to be able to run
the software it describes.


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