> DOS didn't have certain protections because the hardware it targeted did not have those protections. For UNIX on the same machines, they also had no such protections. On 8086 there were no CPU rings, no virtual memory and no other features to help there.

Those arrived with the 386 (286? Don't remember but 386 for sure) and DOS was well alive late into the 386 and even late in the 486 days.

> For UNIX on the same machines, they also had no such protections.

I was already running Linux on my 486 before Windows 95 arrived. Linux and DOS. One had those protections, the other didn't.