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For those of you who’ve been living under a rock, or just not that familiar with what Coherent is, it’s a clean room re-implementation of version 7 Unix. What is unique about Coherent is that AT&T sent a team, which included Dennis Ritchie to evaluate the source to make sure that they hadn’t stolen Unix, and they concluded:

“that looking at various corners I couldn’t find anything that was copied.”

So Coherent was free to continue to sell their discount Unix like OS for the bargain price of $99 USD. I had plans on buying a copy as the older versions even supported the 8086, and 80286 however by the time I finally got enough RAM and disk space to make the purchase worth while, Linux was freely available. I believe that Coherent was the first OS to be killed by the Linux juggernaut, followed by SCO Xenix.

So it’s a little late to the party, open sourcing may have helped back in the early 1990’s although it’d seem like an utterly crazy move at the time.
Better late than never, this includes source dumps, and some RCS data, along with random tgz’s and a binary distribution of version 4. Without any doubt this will either help emulators better emulate the machine state Coherent expects, or perhaps fixing Coherent to run on more modern machines.

Coherent was also famous for it’s large, and well documented manual. Luckily the sources to the manual are also available.

So without further ado, here is the pages with the sources to coherent.

On final note of interest is that the Mark Williams Company was founded by Robert Swartz, who’s son Aaron was quite influential until the time of his death.