RISC OS, the computer operating system developed by Acorn Computers for their ARM-based Acorn Archimedes range, was originally released in 1987 as , and soon followed by , and . The next version, , became and was completed and made available in April 1989. was released with the very earliest version of the A5000 in 1991 and contained a series of new features. By 1996 RISC OS had been shipped on over 500,000 systems. was released by RISCOS Ltd (ROL) in July 1999, based on the continued development of . ROL had in March 1999 licensed the rights to RISC OS from Element 14 (the renamed Acorn) and eventually from the new owner, Pace Micro Technology. According to the company, over 6,400 copies of on ROM were sold up until production was ceased in mid-2005. was launched in May 2001 by ROL. This is a subscription scheme allowing users access to the latest OS updates. These upgrades are released as soft-loadable ROM images, separate to the ROM where the boot OS is stored, and are loaded at boot time. was shipped in May 2002, with following in November 2002 and the final release of in June 2004. ROL released the ROM based the same month, dubbed as a play on the RISC OS GUI convention of calling the three mouse buttons 'Select', 'Menu' and 'Adjust'. ROL sold its 500th Adjust ROM in early 2006. was released in October 2002 on Castle Technology's Acorn clone Iyonix PC. is a separate evolution based upon the NCOS work done by Pace for set-top boxes. In October 2006, Castle announced a source sharing license plan for elements of . This Shared Source Initiative (SSI) is managed by RISC OS Open Ltd (ROOL). RISC OS 5 has since been released under a fully free and open source Apache 2.0 license, while the older no longer maintained RISC OS 6 older has not. was also announced in October 2006 by ROL. This is the next generation of their stream of the operating system. The first product to be launched under the name was the continuation of the Select scheme, . A beta-version of , (), was available in 2007 as a free download to all subscribers to the Select scheme, while in April 2009 the final release of was shipped. The latest release of RISC OS from ROL is , shipped in December 2009. Arthur The