What percent of Unix users are using a "modern OS" and what percentage are using Linux, which hasn't significantly changed since it was released in 1994?
My point was that most people are using things like Linux, MacOS, etc. nowadays, which are all also pretty old by now but not nearly as old as ATT Unix
Linux has changed dramatically since its first release. It has major parts rewritten every decade or so, even. It just doesn't break its ABI with userspace.
Of course, I meant the design hasn't changed. Linux has had a lot of refactoring, and probably Windows has also.
let's be charitable, removal of global lock was fairly big change.