Creating a new shell

Please forgive me for my bad explanation, I'm relatively new to creating operating systems and "new shells".

Basically, I've seen different operating systems use shells other than CraftOS, even after exiting a file. Any help is very, very appreciated. Thanks!

If a script starts another script (eg, via shell.run()), then when the second script ends, the first will automatically carry on from where it left off.

This is down to the way scripts are launched: they're first compiled up into a function, and then that function is simply executed. Whenever a function returns, the code which called it then continues.