I was always fond of the Jupiter Ace [1] which was a Sinclair ZX-81 clone made in the UK in the early 80s. It had FORTH in ROM as the system language and operat

I was always fond of the Jupiter Ace [1] which was a Sinclair ZX-81 clone made in the UK in the early 80s. It had FORTH in ROM as the system language and operating system/interface, rather than BASIC. > ACE's Forth was based mostly on Forth-79, with some relevant differences. Runtime error checking could be turned off to further raise speed by 25% to 50%. [...] The ACE's dialect of FORTH introduced several innovations. [I]t added syntax checking to control structures and definer constructions [...] as well as decompiling capabilities. I think they only sold about three of them; I certainly never saw one in the shops. It was overtaken by machines like the BBC B, Commodore 64 and ZX Spectrum 48k, which were better specced (more than 1Kib RAM, colour output etc.) and had more software. Even the ZX-81, which I owned at one point and programmed in its idiosyncratic BASIC (including features like using the screen buffer as a few extra bytes of scratch memory!) was more popular. But, a nice idea, and I keep scanning eBay to try and find one to buy second-hand, just to see what they were like... [1] https://en.wikipedia.org/wiki/Jupiter_Ace https://en.wikipedia.org/wiki/Jupiter_Ace