RISC OS is an operating system that runs on desktop computers and embedded gadgets that use ARM-compatible processors. It is quite a niche computer platform with perhaps a few thousand users; nevertheless, it is possible to browse the web, send emails, produce documents and artwork, use USB devices, share files with networked non-RISC OS computers, port Unix-compatible software, and plenty more, thanks to efforts by a number of organisations and individual developers.

RISC OS was created by Acorn Computers for its range of microcomputers produced between the late 1980s and the mid-1990s. The company, which gave birth to processor design giant ARM, was broken up in 1998, but the platform continues to survive. The last version of RISC OS released publicly by Acorn was version 3.8. A number of emulators have emerged since so people who want to run their favourite RISC OS applications on Windows, Mac OS X, Linux and other platforms can do so. For more information on RISC OS, you can browse the Drobe news archives and follow the links to more online resoures, read the articles on riscos.info and iconbar.com, or browse through the links below...

RISC OS Open

RISC OS Open is an ongoing project, launched in 2006, to publish the source code to RISC OS and bring third-party programmers onboard to update the operating system, port it to new ARM-powered hardware, fix bugs and generally place development in the hands of users. The blueprints are not available under a traditional open source licence, but some developers are happy to contribute under the terms of the project's shared source licence. RISC OS Open also periodically releases new free-to-download pre-built versions of RISC OS 5 and its bundled applications from the community-developed sources. Work is underway to complete a port of ROS 5 to hardware that uses the ARM Cortex family of processors.

RISCOS Ltd

After the break-up of Acorn, the RISC OS technology was shared among a handful of companies to continue using. RISCOS Ltd was formed in 1999 using investment from the community and was granted a licence to develop the OS for the desktop computer market. The company's directors have since asserted that ROL has been allowed to expand this remit. RISCOS Ltd produced RISC OS 4, which is compatible with Acorn RiscPC-class machines, the AdvantageSix A9home, RiscStation computers and the Microdigital Mico and Omega. The OS can be bought as a one-off upgrade or users can subscribe to Select, a scheme that pushes updates to customers who have pre-paid for releases. In 2006 ROL released RISC OS 6 for Acorn RiscPC-class machines - they leapfrogged over version 5 for the reason given below.

Castle and the Iyonix

In 2002, a company called Castle launched the Iyonix range of desktop computers, which used the Intel ARM-compatible XScale IOP321 processor. The machine shipped with RISC OS 5, which was derived from a version of RISC OS held by consumer electronics manufacturer Pace Technology, one of the companies that obtained access to the RISC OS technology from Acorn. In 2003, Castle bought this technology from Pace, and eventually made the product's source code available through the RISC OS Open project. The Iyonix product line was discontinued in 2008.

VirtualRiscPC

Developed by VirtualAcorn, VirtualRiscPC is a software product for Microsoft Windows and Apple Mac OS X users that emulates Acorn RiscPC-class hardware, allowing RISC OS 4 and 6, and RISC OS applications, to run on non-ARM-powered computers. On modern Intel-powered machines, RISC OS on emulated hardware often outperforms RISC OS running on native ARM-powered kit.

RPCEmu Spoon

RPCEmu is another RiscPC-class hardware emulator, although it is freely available for the Microsoft Windows, Apple Mac OS X and GNU/Linux platforms and is open source. RPCEmu can run RISC OS 3, 4 and 6, and a RiscPC-compatible build of RISC OS 5. It was created by Tom Walker, and after he stepped back from the project, Peter and Matthew Howkins tidied up the source code, added new features and created their own flavour of the software, calling it RPCEmu Spoon. Tom Walker also produced Acorn Archimedes-class emulator Arculator; other pre-RiscPC-era hardware emulators include ArcEm and Red Squirrel - the latter being a freely available predecessor of VirtualRiscPC.