RISC OS is a light, open-source operating system for ARM based computers, it has been around since the 1980s. It pre-dates both Windows and Mac OS and includes many revolutionary features that have ultimately been used in many other operating systems.

RISC OS 5 is the latest version of the operating system and is developed by RISC OS Open Ltd. RISC OS 5 supports legacy systems (26-bit – pre-2002) such as the RiscPC and A7000 as well as newer 32-bit ARM-based hardware such as Beagleboard, Pandaboard and Raspberry Pi based machines. You can download RISC OS 5 free of charge from the RISC OS Open website.

All Legacy (26-bit) RISC OS computers such as the RiscPC, A7000 etc load the operating system from a physical ROM chip. This is not the case for 32-bit modern RISC OS systems – an example being that you can install RISC OS 5 on a Raspberry Pi by just loading it onto an SD card.

Want to get started with RISC OS? Check out our guide!

Why use RISC OS?

For the majority of users, RISC OS is no longer really up to scratch when it comes to a main operating system for day-to-day tasks – mainly down to its lack of a fully capable web browser that supports Javascript and HTML5 fully as well as lack of wi-fi and multi-core support for systems running on CPUs with multiple cores.

There are however a good chunk of users who prefer RISC OS’ desktop enviroment and do use it for most things as well as using another operating system for things it can’t do so well (web browsing, video streaming etc.)

That said, RISC OS is still a great platform for hobbists and retro gamers, who make up the majority of the RISC OS community.


RISC OS’ huge back catalogue of games from the Acorn Archimedes days (check out JASPP for tons of free games!) is a big reason why people either come back to the platform or keep using it.

As well as RISC OS native retro titles, there’s a good chunk of games that have been ported to RISC OS from Linux and other platforms (Doom, Quake, Battle for Wesnoth to name a few). New games are being developed and released on RISC OS all the time, both free and commercial titles.

For more information about gaming on RISC OS, check out Games Corner.

Hobbyist computing

RISC OS is a very small and resource-efficient operating system. It will happily run on a machine with a few Megabytes of RAM rather than Gigabytes while still giving you a fully operational desktop with networking. The 1GB of RAM that comes with a Raspberry Pi, while quite small for most modern operating systems, is more than what’s needed for the vast majority of use cases.

Unlike most operating systems, RISC OS is very barebones by default – it’s up to you to add and configure everything the way you like it, you get the basics such as a web browser (Netsurf), package managers, text editor etc. but then it’s down to you to install everything from an on-screen clock to an email application or SSH client.

A big chunk of modern RISC OS applications these days are open source and developed by RISC OS hobbists. A lot of apps are written by users who needed an application for their own use but found there wasn’t anything on RISC OS for it, so they wrote one (e.g. Murnong for downloading YouTube videos or Manga for reading online manga comics).

There’s also an active community built up of developers, users and commercial businesses that all work on improving RISC OS, developing existing and new apps for it as well as porting RISC OS to new hardware (e.g. the Raspberry Pi and Wandboard).

The BBC BASIC programming language is also built into the operating system, which makes it a great platform for programming and understanding how code works in conjunction with the operating system and vice versa.


Between 1987 and 1998, RISC OS was bundled with every ARM-based computer manufactured by Acorn Computers. It was made especially popular by the Acorn Archimedes range, which was deployed in most educational institutes in the UK during the early to mid 90s.The Archimedes as well as the RiscPC was also widely deployed in TV and radio production enviroments in the UK as well as parts of Europe and even North America.

After the break-up of Acorn in 1998, development of RISC OS was forked and separately continued by several companies, including RISCOS Ltd, Pace Micro Technology and Castle Technology.

The last version of RISC OS made by Acorn Computers was 3.7. RISCOSLtd. released RISC OS 4 in 1999 after taking over the rights to the operating system alongside Castle Technology – who continued to produce the RiscPC and A7000 range of computers after the closure of Acorn.

RISC OS 5 from Castle Technology was released in 2002 with the launch of the Iyonix, the first 32-bit RISC OS computer – all previous machines were 26-bit.

RISCOS Ltd. released RISC OS 6 in 2006 but despite its name, it is actually incompatible with 32-bit RISC OS computers and would only run on older, 26-bit computers. Development of 26-bit only versions of the operating system – RISC OS 4 and 6 – have largely halted as of the year 2017.

Nowadays, RISC OS 5 is bundled with a number of ARM-based desktop computers and is constantly being developed further by RISC OS Open – who were responsible for porting RISC OS 5 to the Raspberry Pi as well as other well-known ARM-based boards. RISC OS 5 is shipped with the NOOBS Starter Pack SD card that comes with many Raspberry Pis.

After operating under a Shared Source agreement since 2008, RISC OS was made fully open source in October 2018 after the buyout of Castle Technology. The operating system is now licensed under Apache License 2.0.