Because it's quite difficult to find a PDP10 or DECsystem-20 today... https://en.wikipedia.org/wiki/TOPS-10 https://en.wikipedia.org/wiki/TOPS-10 https://en.w

Because it's quite difficult to find a PDP10 or DECsystem-20 today... https://en.wikipedia.org/wiki/TOPS-10 https://en.wikipedia.org/wiki/TOPS-10 https://en.wikipedia.org/wiki/TENEX_(operating_system) https://en.wikipedia.org/wiki/TENEX_(operating_system)