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|Developer||Acorn Computers (Arthur 1.x-3.7), RISCOS Ltd (4.02-6.20), RISC OS Open Ltd (5.x)|
|Source model||Closed source (6.x), Open source (5.x)|
|Initial release||Arthur 1.20|
|Latest release||RISC OS 6.20 |
|Latest preview||RISC OS 5.29 |
|License||Proprietary (RISC OS 6.x), Apache License 2.0 (RISC OS 5.x)|
RISC OS is an operating system developed by Acorn Computers, initially released as Arthur for their Archimedes line of machines, and later on, their RiscPC line as well. After the downfall of Acorn in 1998, the code of the operating system was forked and being maintained by different companies, such as RISCOS Ltd, Pace Micro Technology and Castle Technology.
In July 1999, RISCOS Ltd released RISC OS 4, based on the code for RISC OS 3.80, and it includes various improvements into the operating system, such as long file name support, a better file system and more.
In May 2001, the company introduced the RISC OS Select scheme, a subscription based service that allows users to get OS updates. In June 2004, the company released RISC OS Adjust (version 4.39), introducing user customization. Further Select releases were under RISC OS Six, as the first version of Select 4 was released to subcribers for free on 2007. RISC OS Six introduced a lot of improvements and changes to the operating system. The final Select release (6i1) was on December 2009, with improvements for configurations as well as Paint and Task Manager, among others.
In 2002, Castle Technology released RISC OS 5 for their Acorn clone, Iyonix PC, which ran on an Intel XScale ARM processor. Altough most software were updated, a few can only run on an emulator called Aemulor, since the processor can't support 26 bit addressing modes.
In 2006, Castle Technology announced a shared source license with RISC OS Open Ltd. (ROOL) for RISC OS 5. In 2018, RISC OS Developments aquired the rights of RISC OS 5 and relicensed it under Apache 2.0.
Currently, it was being maintained by RISCOS Ltd. and the RISC OS Open community. It can be currently run on OMAP3 BeagleBoard, Raspberry Pi, A7000/A7000+, RiscPC, OMAP4 PandaBoard, Titanium and the Iyonix, with an upcoming port for the WandBoard and OMAP5.
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Note: All stable builds are in even numbers.