This documentary/ad from AT&T in the 1970s has Bell Labs employees introduce and describe how Unix differs from other operating systems, as well as about the ethos of Unix. Related is the Computerphile interviews with Brian Kernighan who participated in this era of Bell Labs (and this video quite excellently).

It’s impressive how they managed to build so much fundamental concepts and designs in such a short period of time. Much of the computing world is still based on how those original Unix programs were written and the decisions of those working in Bell Labs.