You can't trust code that you did not totally create yourself.
It's always good to take an orthogonal view of something. It develops ideas.
In fact, we started off with two or three different shells and the shell had life of its own.
SCCS, the source motel! Programs check in and never check out!
I wanted to avoid, special IO for terminals.
FORTRAN was the language of choice for the same reason that three-legged races are popular.