Jonesforth is a great tool when trying to teach people how stack based interpreters would work. I used it as an example in a class that I taught. The document

Jonesforth is a great tool when trying to teach people how stack based interpreters would work. I used it as an example in a class that I taught. The documentation is first rate with exact descriptions in the code. As far as the FORTH being a horrible language, to some extent it is. But if you are stuffing into a small chipset it's good. Granted there are things like Lua now, but back in the early years, FORTH was a huge tool for imbedded systems.