RISC OS was designed and developed by Acorn Computers, once dubbed the Apple of Britain, in the 1980s to run on the fledgling 32-bit Arm processor family, also designed by Acorn. Yes, the Arm that now powers the world's smartphones, embedded electronics, Internet-of-Things, and more, although it's come a long way since its mid-1980s genesis.

The operating system, meanwhile, began life as the rough-around-the-edges Arthur 1.20 in 1987 for the ARM2-powered Archimedes A305 and A310, and by 1989, had morphed into the more slick RISC OS 2, written mostly in handcrafted assembly language for performance and memory-footprint reasons.