RISCOS Ltd

RISCOS Ltd was formed to continue end-user-focused development of RISC OS after the de-listing of Acorn Computers, following its purchase by Morgan Stanley Dean Witter in order to benefit from the shareholding that Acorn held in ARM Ltd. In March 1999, RISCOS Ltd obtained exclusive rights to develop and sell RISC OS 4 for the desktop market from Element 14. A few weeks later Pace purchased Acorn's Cambridge headquarters and staff for £200,000 and then continued to develop its own, in-house version of RISC OS, primarily for set-top boxes and other embedded devices.

At the time of the company's formation, it was noted that having access to the source code could facilitate removal of the OS's dependence on Acorn's proprietary chips. This simplifies entry to the hardware market by new companies.

On 29 January and 14 May 2013 RISCOS Ltd was listed in the London Gazette: on 14 May 2013 it was struck from the register of companies and dissolved. The rights to all versions of RISC OS previously developed and marketed by RISCOS Ltd were purchased by 3QD Developments Ltd, the maker of VirtualAcorn.

RISC OS 4

RISCOS Ltd completed work on RISC OS 4 and in July 1999 it was released as an upgrade for existing machines, priced at £120. Improvements include support for long filenames, larger disk sizes and partitions, along with a new desktop look.

Work then continued on a system of soft-loaded updated versions of the OS, released under an annual subscription release scheme named RISC OS Select in 2002.

In 2004, the company replaced its baseline RISC OS 4.02 product with an updated version of the OS named RISC OS Adjust. This version of RISC OS was based on version 4.39, or Select Edition 3 Issue 4, of the company's Select scheme. In the same year, RISCOS Ltd agreed to produce a fully 32-bit-compatible version of RISC OS Adjust for Advantage Six's A9home product. The A9home was released in May 2006 after a 12-month beta-testing process, although the build of Adjust 32, namely RISC OS 4.42, is not feature-complete.

RISC OS Six

RISC OS Six was intended to represent the next generation of RISCOS Ltd's operating system. Significant improvements in portability, stability and internal structure, including full 26/32-bit neutrality, were to lay the foundation for the company's future releases. In October 2006, a beta version of RISC OS Six was made available for download by subscribers to the Select programme. The first full release of RISC OS Six was made available in early 2007. The final release of RISC OS Six was RISC OS 6.20, in December 2009.