Lost Unix v4 Possibly Recovered on a Forgotten Bell Labs Tape From 1973

'A tape-based piece of unique Unix history may have been lying quietly in storage at the University of Utah for 50+ years,' reports The Register. And the software librarian at Silicon Valley's Computer History Museum, Al Kossow of Bitsavers, believes the tape 'has a pretty good chance of being recoverable.'

Long-time Slashdot reader bobdevine says the tape will be analyzed at the Computer History Museum. More from The Register:

The news was posted to Mastodon by Professor Robert Ricci of the University of Utah's Kahlert School of Computing [along with a picture. 'While cleaning a storage room, our staff found this tape containing #UNIX v4 from Bell Labs, circa 1973...' Ricci posted on Mastodon. 'We have arranged to deliver it to the Computer History Museum.'] The nine-track tape reel bears a handwritten label reading: UNIX Original From Bell Labs V4 (See Manual for format)...

If it's what it says on the label, this is a notable discovery because little of UNIX V4 remains. That's unfortunate as this specific version is especially interesting: it's the first version of UNIX in which the kernel and some of the core utilities were rewritten in the new C programming language. Until now, the only surviving parts known were the source code to a slightly older version of the kernel and a few man pages — plus the Programmer's Manual [PDF], from November 1973.
The Unix Heritage Society hosts those surviving parts — and apparently some other items of interest, according to a comment posted on Mastodon. 'While going through the tapes from Dennis Ritchie earlier this year, I found some UNIX V4 distribution documents,' posted Mastodon user 'Broken Pipe,' linking to tuhs.org/Archive/Applications/Dennis_Tapes/Gao_Analysis/v4_dist/.
There's a file called license ('The program and information transmitted herewith is and shall remain the property of Bell Lab%oratories...') and coldboot ('Mount good tape on drive 0...'), plus a six-page 'Setup' document that ends with these words...

We expect to have a UNIX seminar early in 1974.
Good luck.
Ken Thompson
Dennis Ritchie
Bell Telephone Labs
Murray Hill, NJ 07974

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