The folks at Bell Labs were asked to figure out if Mark Williams had copied Unix directly or via too much knowledge already obtained, or whether it was truly a clean room recreation. I don't remember all the details, but it became clear after a while that it was indeed a reasonably clean rewrite.This was done by looking for corner cases that were an accident of the original implementation and would be unlikely to appear in a version created separately. One detail that did stick with me was the discovery during this process that ppt, the paper tape simulator, mispunched a letter, I think "R", but the Mark Williams version did not. Was that compelling? Not on its own, but it was funny and memorable.-robOn Sun, May 1, 2022 at 9:46 PM Ron Natalie <ron@ronnatalie.com> wrote:Mark Williams Coherent was one I worked with on the PC many years ago.
> On May 1, 2022, at 11:34, Andrew Warkentin <andreww591@gmail.com> wrote:
>
> What was the first "clone" functional Unix (i.e. an OS not derived
> from genetic Unix code but highly compatible with genetic Unix)? Idris
> is the earliest such OS of which I am aware (at least AFAIK it's not a
> genetic Unix), but was it actually the first? Similarly, which was the
> first "outer Unix-like" system (i.e. one with strong Unix influence
> but significantly incompatible with functional Unix)? Off the top of
> my head the earliest such system I can think of is Thoth (which
> predates Idris by almost 2 years), but again I'm not sure if it was
> actually the first.