Unix v4 Tape Found

Anyway, since nobody much seems to realise this is quite a big deal, I will share the explainer I wrote yesterday:

https://www.theregister.com/2025/11/07/unix_fourth_edition_t...

Unix V4 is otherwise lost. It was the first version in C.

Please let there be an ultimate force in the universe that spared this tape from tape degradation and/or magnetization that it can be read and extracted into a raw dump fs that we can preserve for all time. (fingers crossed)

Tapes from back then haven’t held up over the years. It all depends on the environment it was stored in.

Someone in the Mastodon thread mentioned the Andrew Tannenbaum "Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway."

So I wondered about a modern day equivalent, looked up 1tb micro-sd cards (sold locally for Nintendo Switch) and calculated that there'd be roughly space for 400 exabytes of data in a shipping container filled to the brim with SD-cards.

(SDcard being 1tb for 1.092 x 1,499 x 0,102 CM's and a shipping container being 1203 x 235 x 239 CM's inside so holding 400 million SD cards)

> It is a '70s 1200ft 3M tape, likely 9 track, which has a pretty good chance of being recoverable.

Not old enough to have this kind of knowledge or confidence. I wonder if instead one day I'll be helping some future generation read old floppies, CDs, and IDE/ATA disks *slaps top of AT tower*.

This seems to be how a lot of modern history is found.

I recently got to talk to a big-ish name in the Boston music scene, who republished one of his band's original 1985 demos after cleaning the signal up with AI. He told me that he found that tape in a bedroom drawer.

I remember at one point I browsed tuhs.org in an attempt to find the source code for the original B (the language predating C) compiler. I don't think it should be in the 4th edition. I still wonder if there's a copy somewhere. I know there are a few modern implementations, but it would be interesting to look at the original.

OT - Mastodon is seriously cool. If you haven't yet bothered, I suggest to everyone that you spend a bit of time exploring.

I really, really hope data can be recovered from this. I’ve read a bunch of the original sources, and such an ancient C would be especially interesting to study.

Very proud to have had this found at my University :-)

That is a big deal; I don't remember anything that old being available on tuhs.org.

Will not be much different to the existing v5 source code, we can assume. https://minnie.tuhs.org/cgi-bin/utree.pl?file=V5/usr/source/...

From 1973. See https://en.wikipedia.org/wiki/List_of_Unix_systems

This is amazing news for UNIX fans. Really hope the source can be recovered and put alongside the other historical UNIX source that's out there.

Very interesting storage format too - Those tapes actually held quite a bit of data (comparatively) - around 45MB (Although this one is shorter ~1000ft and probably carries about 10-15MB which is close to V4's source code, binary and documentation size).

What are the odds that a medium like that has successfully stored the full data without error?

For context, I'm a geezer who got early access reading Lions' Commentary (6th Edition) and comparing it with 7th Edition source (running on a PDP-/something with no more than 128 KiB RAM). That was 1985, as Unix was spreading its way through universities. SIGSEGV haunts me to this day.

That was a full 40 years ago. And yet, 4th Edition is ancient history even to me.

Hope they will upload it to archive.org and Software Heritage.

Finally we can see the naughty stuff they recorded!

Other posts on this subject, none with discussion:

https://news.ycombinator.com/item?id=45846438

https://news.ycombinator.com/item?id=45844876

https://news.ycombinator.com/item?id=45842643