[TUHS] Unix v5 and beyond

Mark Longridge cubexyz at gmail.com
Sun Jul 13 14:36:45 AEST 2014

Hi folks,

I'm interested in comparing notes with C programmers who have written
programs for Unix v5, v6 and v7.

Also I'm interested to know if there's anything similar to the scanf
function for unix v5. Stdio and iolib I know well enough to do file IO
but v5 predates iolib.

Back in 1988 I tried to write a universal rubik's cube program which I
called unirubik and after discovering TUHS I tried to backport it to
v7 (which was easy) and v6 (which was a bit harder) and now I'm trying
to backport it to v5. The v5 version currently doesn't have the any
file IO capability as yet. Here are a few links to the various


Also I've compiled the file utility from v6 in v5 and it seemed to
work fine. Once I got /dev/mt0 working for unix v5 (thanks to Warren's
help) I transferred the binary for the paging utility pg into it. This
version of pg I believe was from 1BSD.

I did some experimenting with math functions which can be seen here:


This will compile on unix v5.

My initial impression of Unix v5 was that it was a primitive and
almost unusable version of Unix but now that I understand it a bit
better it seems a fairly complete system. I'm a bit foggy on what the
memory limits are with v5 and v6. Unix v7 seems to run under simh
emulating a PDP-11/70 with 2 megabytes of ram (any more than that and
the kernel panics).

Also I'd be interested in seeing the source code for Ken Thompson's
APL interpreter for Unix v5. I know it does exist as it is referenced
in the Unix v5 manual. The earliest version I could find was dated Oct
1976 and I've written some notes on it here:


Ok, that's about it for now. Is there any chance of going further back
to v4, v3, v2 etc?


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