Minimal FORTHs (https://en.wikipedia.org/wiki/Forth_(programming_language) https://en.wikipedia.org/wiki/Forth_(programming_language)) can run on an unexpanded

Minimal FORTHs (https://en.wikipedia.org/wiki/Forth_(programming_language) https://en.wikipedia.org/wiki/Forth_(programming_language)) can run on an unexpanded VIC-20 (5K) or even early TRS-80 Model 1 (4K) -- with room and functionality to spare... On the VIC-20, you even get a few colors!