I came across a link an online version to Leo Brodie’s Forth tutorial, “Starting Forth” today. I used to have a copy of that book eons ago. I learned how to program on a Commodore VIC-20 and I bought (actually had to special order it) a Forth language cartridge. This book has been out of print for decades, the online version is probably the only way to read it now.
Forth is an arcane language that allows you to program in interactive and iterative manner. You would create words (what other languages would call functions or subroutines) from the language core keywords and created new words from existing words.
The operators worked in post-fix notation (aka reverse Polish notation) like the older HP calculators. The language was stack oriented and post-fix works well when you are pulling items off the stack.
Since Forth programs were very small in size and typically do not access or require a traditional file system, Forth was used in embedded controllers and other hardware related projects. NASA uses Forth to this day for spacecraft flight system controllers and other projects.
Needless to say Forth and the VIC-20 were not the best fit and I never did too much with it. I wonder how many geek points do you get for programming in Forth on 5K (but only 3.5k were usable) machine that had a whopping 22 columns of text per line?