Acorn Archimedes ARM Arthur RISC OS GUI operating system
In 1987, Acorn launched the Archimedes range of high-performance home computers in Europe and Australasia. Based on their own 32-bit ARM RISC processor, the systems were shipped with a GUI OS called Arthur. In 1989, Arthur was superseded by a multi-tasking GUI-based operating system called RISC OS. By default, the mice used on these computers had three buttons.
