Acorn Archimedes’ operating system Arthur is told to stand for “A Risc-based operating system by THURsday,” reflecting the extraordinary short time it took to finish it. The rumour has it that ArthurOS was a quickly devised replacement for the original system ARX, which failed to materialize.
By the second version of ArthurOS, Acorn decided to rename it RISC OS because of the movie “Arthur 2: On the rocks,” which just premiered in the cinemas.
The characteristic blue/orange/blue/red colour scheme of ArthurOS is typically referred to as “technicolour.”
There were several computers having a complete GUI in their Read-Only Memory, ready to be used instantly after powering on. The list includes 1990’s Macintosh Classic (with built-in System 6.0.3), Atari ST (excluding very early editions of 520ST with TOS on a floppy disk) and Acorn machines with RISC OS.