Could you also tell me how OS X evolved in a similar style to that?
For arguments sake - Platform wise.
My knowledge of Mac is not as good as those of Microsoft because I was a self-convert, Mac/Hybrid user since 2004. Here is the best of my memory:
1. OS X's kernel is UNIX based. UNIX's history can be traced all the way back to 70s (not 80s). Mach is a Micro Kernel flavor of UNIX, which found its way to OS X (Darwin).
2. Current OS X kernel is a hybrid kernel. This is the same philosophy as NT kernel. Some say NT kernel is technically superior than any current UNIX/LINUX kernels, which I believe is very possible.
3. The UI of OS X (Cocoa Framework) was originated from NextSTEP, a company started by SJ. Apple bought NextSTEP in 1996, and that's how SJ went back to Apple.
4. OS X was Apple's answer (or solution) to save itself from the long lasting OS crisis as Apple never had a mature OS that could run with protected memory and preemptive multi-tasking before OS X. The Copland was nothing but a failure in term of software development.
5. OS X versions:
10.0 Public Beta ~ 10.1: These are pretty much considered betas for most users back then. OS 9 was still the main system for most users.
10.2: first "really usable" version of OS X by most users' opinion.
10.3: I was sold on this one because and only because of Exposé.
10.4
10.5
Mac OS 9 and before had no protected memory at all. Apple could hold on during those days only because they had one thing Microsoft and Intel did not have: PowerPC chips back then was more than twice as fast as x86. That is very important for people run applications like Photoshop in those old days.
For a detailed view of OS X and its full history, this guy knows it inside out.
http://www.kernelthread.com/ 