RISC OS

RISC OS is a proprietary, modular, single-user, multitasking operating system originally designed by Acorn Computers Ltd in Cambridge, England. First released in 1987 as Arthur 1.2, it was subsequently renamed RISC OS 2 and became the standard operating system for Acorn's Archimedes range of computers, which were based on the ARM (Acorn RISC Machine) processor.

RISC OS is known for its speed, compact size, and graphical user interface (GUI), which uses a windowing system but departs from many common conventions found in other operating systems. A key characteristic is its reliance on the mouse, with most operations accessed through menus and click-based actions. It also employs a file system where files are identified by their type, rather than solely by filename extensions.

Following Acorn's demise in 1998, development of RISC OS has been continued by various companies, including RISCOS Ltd and Castle Technology Ltd. The operating system has been ported to various ARM-based hardware platforms, including single-board computers like the Raspberry Pi.

RISC OS is still actively maintained and developed by a dedicated community of enthusiasts and developers. It remains a niche operating system, but it retains a loyal following attracted by its speed, efficiency, and unique design. It finds use in areas such as education, hobbyist computing, and embedded systems.