Say Something About UNIX
I was always lost when talking about UNIX/Linux. Now I know the difference and connection between them better after asking google.
UNIX was first developed by Richie and Thompson in the 1960’s from AT&T, many groups contribute to it then, including Berkeley’s BSD. AT&T realized UNIX’s value then, and claim its ownership. However, BSD contributed much to it, so as a compromise, BSD could release their own code. Up to now, there are two main branches, AT&T has full ownership, and BSD has partly. It was then AT&T seperate UNIX and sold it to Novell which then sold it to SCO. The copyright was also granted to IBM, HP, and SUN. They can also modify the source code.
Linux was developed when BSD and AT&T engaged in the lawsuit about the copyright about UNIX, it was free and open, so many developers join to develop. Linux learned some features but it does not rely on UNIX, in which way it is defined as a UNIX-like OS.
We can have a look at the full hierarchy of UNIX: