I remember writing a fairly trivial program in Forth on a ZX81 for a school open day. You needed the 16K RAM pack thing with the usual lump of Blu Tac to stop it wobbling.
When I "discovered" Forth, it seemed like science fiction (soo fast!) to me after BASIC juddering around the screen.
Probably worth mentioning the Jupiter Ace here[0] - a ZX81/Spectrum era computer which had Forth in ROM, instead of BASIC which was common at the time. The basic model only had 1K of RAM. I never used one but I remember when it came out, reviewers commented on its speed and memory efficiency.
When I "discovered" Forth, it seemed like science fiction (soo fast!) to me after BASIC juddering around the screen.