The other environment that is still popular today is the “statistical environment” that Rick Becker, Allan Wilks, and John Chambers created. It eventually became “S” and John would essentially recreate it as “R.” It’s a very nice environment for performing statistics and graphics together.

A shell is just how you interact with the underlying system. The gui is also a shell. Confusing I know!

E.g. the Windows GUI is the “Windows Shell,” not be confused with the Windows Command Line which is one (well, many) application within the shell.

I like to see it this way: A shell /wraps/ the kernel. You cannot issue system calls directly, but a program that handles user input generically (and ideally dynamically), can do this for you. A desktop environment, Emacs, and to an increasing degree web browsers are all different "shells".

A shell is a program dedicated to allowing an operator to launch other programs. It can be as simple as a menu or as complex as a COM-interfaceable GUI with graphical desktop metaphor. It's often configured to but not strictly required to automatically launch on user login.

Any user-space executable can issue system calls, the shell isn't special there.

Like valence shells on atoms. I dig it

Maybe something like Jupyter? Text documents with sections of code or commands?