[pjmlp]

Actually on Windows a process is a thread with additional information.

The unit of execution is the thread.

On the UNIX world it depends on which UNIX you are talking about.

Linux has a similar model to Windows NT nowadays, hence clone() as key primitive.

Other UNIXes have different approaches.

[PaulDavisThe1st]

I worked on the kernel of DEC Ultrix, Mach/BSD and a couple of other early Unixen. The approach in all the ones I worked on was broadly the same.