Discover Unique UNIX V4 Source Code Recovered from Magnetic Tape

A Significant Discovery for Computer Science History

UNIX version 4 is considered special because it was the first UNIX variant written in C, rather than in PDP-11 ASM. For a long time, it was thought to be lost; however, a magnetic tape over fifty years old, found in a storage facility at the University of Utah, actually contained the UNIX v4 source code.

According to a report by Tom's Hardware, [Al Kossow] from Bitsavers successfully recovered the data by reading the raw data stream from the tape head and using the ReadTape program to reconstruct the stored information. Although the tape was old and data integrity was not guaranteed, it turned out that not only was the tape largely empty, but the existing data was in good condition.

The recovered files can be found on Archive.org, which hosts several gigabytes of raw data from the tape, including files in SimH format and the associated file system. It is clear that UNIX v4 can only be run on a PDP-11 system or an equivalent emulator, but for those interested in its modern successors, the BSD Unix version, FreeBSD, is an excellent option.