Working with the venerable ed editor, (preceded by qed) by Ken Thompson of ATT > Google, I'm reminded a bit of the past events which led us to where we are today pre-Unix.
Short and sweet and very over-simplified!
Two different cultures starting with CTSS and ITS eventually meet. CTSS morphed into Multics, which morphed into Unix. Forced to license os research by being granted a monopoly on phone/comm tech, ATT had to share with uni's and corporations that were willing to pay an exhorbitant license. The rest is history we all probably know.
https://en.wikipedia.org/wiki/Compatible_Time-Sharing_SystemITS was the free wheeling opposite of CTSS and Multics, lotsa LISP, and the eventual blowout of the MIT AI lab, where RMS got really pissed off when that free-wheeling anarchistic sharing environment just switched sides on him. Which got us emacs and gcc and gnu and the rest is history...
https://en.wikipedia.org/wiki/Incompatible_Timesharing_SystemWhich of course leads to Tinycore. All this from being reminded by the ed editor where we came from.