Editing RISC OS

{{Short description|Computer operating system by Acorn Computers Ltd.}}
{{About|the operating system developed by Acorn Computers Ltd|the OS developed by MIPS Computer Systems|MIPS RISC/os}}
{{Use dmy dates|date=January 2025}}
{{Use British English|date=April 2013}}
{{Infobox OS
| name = RISC OS
| logo = RISC OS.png
| logo size = 75px
| screenshot = RISC OS 5.30 screenshot.jpg
| screenshot_size = 300px
| caption = A screenshot of RISC OS 5.30 (released 2024) running on a [[Raspberry Pi]]
| developer = [[Acorn Computers]]
Open-source (version 5)
* [[Castle Technology]]
* [[RISC OS Open]]
Proprietary (versions 4 & 6)
* [[RISCOS Ltd]]
| working state = Current
| source model = [[Closed source]]; [[Open-source software|open source]] for some versions since 2018
| released = {{Start date and age|1987|09|25|df=yes}}<ref name="arthur_os_copyright_note">copyright notice Arthur 1.20 (25 September 1987)</ref>
| latest release version = * 5.30<ref name="ROOL news 2024-04-27">{{cite web |url=https://www.riscosopen.org/news/articles/2024/04/27/risc-os-5-30-now-available |title=RISC OS 5.30 now available |access-date=30 April 2024 |last=Revill |first=Steve |date=27 April 2024 |publisher=[[RISC OS Open]] }}</ref> / {{Start date and age|2024|04|27|df=yes}}
* 6.20 / {{Start date and age|2009|12|01|df=yes}}
| latest release date = 
| latest preview version = 5.31
| latest preview date = 
| marketing target = [[Acorn Computers|Acorn]] [[personal computer]]s
| language = English
| programmed in = [[BBC BASIC]], [[C (programming language)|C]], [[C++]], [[assembly language]]
| update model = [[Flash ROM]], [[Programmable read-only memory|OTP ROM]], or loadable [[ROM image|ROM&nbsp;image]]
| package manager = PackMan, RiscPkg
| supported platforms = [[ARM architecture|ARM]]
| kernel type = [[Monolithic kernel|Monolithic]]
| userland = 
| ui = [[Graphical user interface|GUI]]
| license = {{plainlist|
* [[Apache License 2.0]]<ref>[https://www.riscosopen.org/news/articles/2018/10/22/risc-os-is-open-for-business RISC OS is open for business!] {{Webarchive|url=https://web.archive.org/web/20181022204607/https://www.riscosopen.org/news/articles/2018/10/22/risc-os-is-open-for-business |date=22 October 2018 }}, RISC OS Open Ltd, accessed 23 October 2018</ref> (version 5)
* [[Proprietary software|Proprietary]] (version 6)
}}
| preceded by = [[Acorn MOS|MOS]] (discontinued)<br />[[ARX (operating system)|ARX]] (discontinued)
| succeeded by = 
| website = {{URL|riscosopen.org}} RISC OS Open<br />{{URL|riscos.com}} RISCOS
| date = 
}}
'''RISC OS''' ({{IPAc-en|r|ɪ|s|k|.|oʊ|ˈ|ɛ|s}})<ref name="acorn_developer_news_issue14">{{cite news | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/DN/Acorn_DevNL14.pdf | title=RISC OS | work=ISV Department news from Acorn | publisher=Acorn Computers Limited | date=May 1989 | issue=14 | access-date=14 February 2021 | pages=2 | quote=It is RISC OS (pronounced risk oh ess, not risk oss) | archive-date=21 May 2021 | archive-url=https://web.archive.org/web/20210521002744/http://chrisacorns.computinghistory.org.uk/docs/Acorn/DN/Acorn_DevNL14.pdf | url-status=live }}</ref> is an [[operating system]] designed to run on [[ARM architecture|ARM]] computers. Originally designed in 1987 by [[Acorn Computers]] of England, it was made for use in its new line of ARM-based [[Acorn Archimedes|Archimedes]] personal computers and was then shipped with other computers produced by the company. Despite the demise of Acorn, RISC OS continues to be developed today by the [[RISC OS Open]] community on version 5.0 of the system that was [[open sourced]] in 2018.<ref>{{Cite news |date=21 June 2022 |title=RISC OS: 35-year-old original Arm operating system is alive and well  |first=Liam |last=Proven |url=https://www.theregister.com/2022/06/21/risc_os_35/ |work=[[The Register]]}}</ref>

RISC OS is a [[Modular programming|modular]] operating system and takes its name from the [[reduced instruction set computer]] (RISC) architecture it supports. It incorporates a [[graphical user interface]] and a [[windowing system]]. Between 1987 and 1998, RISC OS shipped with every ARM-based Acorn computer including the Archimedes line, Acorn's R line (with [[RISC iX]] as a dual-boot option), [[RiscPC]], [[Acorn A7000|A7000]], and prototype models such as the Acorn [[Acorn Computers#NewsPad|NewsPad]] and [[Phoebe (computer)|Phoebe computer]]. A version of the OS, named [[NCOS]], was used in [[Oracle Corporation|Oracle]]'s [[Network Computer]] and compatible systems. 

After the break-up of Acorn, development of the OS was [[Fork (software development)|fork]]ed and continued separately by several companies, including {{nowrap|[[RISCOS Ltd]]}}, [[Pace Micro Technology]], [[Castle Technology]], and RISC OS Developments.<ref name="riscosdev" /> Since then, it has been bundled with several ARM-based desktop computers such as the [[Iyonix PC]]<ref name="Acorn press release 1998-10-12">{{cite press release|publisher=Acorn Computers Ltd |title=Acorn announces distribution deal with Castle Technology for RISC based products |date=12 October 1998 |url=http://www.acorn.co.uk/acorn/news/press/castle.html |access-date=6 January 2011 |quote=(October 12th 1998), Cambridge, UK-Acorn announced today that it has completed negotiations with Castle Technology for them to distribute Acorn products. |archive-url=https://web.archive.org/web/19990506180305/http://www.acorn.co.uk/acorn/news/press/castle.html |archive-date=6 May 1999}}</ref> and [[A9home]]. Most recent stable versions run on the ARMv3/ARMv4 [[RiscPC]], the ARMv5 [[Iyonix PC|Iyonix]],<ref name="Iyonix at a glance RO5 features">{{cite web |url=http://www.iyonix.com/iyonix/features/osfeatures.shtml |title=RISC OS 5 features |access-date=31 January 2011 |publisher=Iyonix Ltd |quote=All IYONIX pcs ship with RISC OS 5 in flash ROM. |url-status = dead |archive-url=https://web.archive.org/web/20101110111706/http://www.iyonix.com/iyonix/features/osfeatures.shtml |archive-date=10 November 2010}}</ref> [[ARMv7]] [[Cortex-A8]] processors<ref name="theinquirer snaps leak">{{cite web |url=http://www.theinquirer.net/inquirer/news/1051924/snaps-leak-risc-os5-beagleboard |archive-url=https://web.archive.org/web/20090519184833/http://www.theinquirer.net/inquirer/news/1051924/snaps-leak-risc-os5-beagleboard |url-status=unfit |archive-date=19 May 2009 |title=Snaps leak of RISC OS5 on BeagleBoard |publisher=[[The Inquirer]] |date=27 April 2009 |access-date=28 June 2011 |last=Farrell |first=Nick |quote=A snap of an RISC OS 5, running on a BeagleBoard device powered by a 600MHz ARM Cortex-A8 processor with a built-in graphics chip, has tipped up on the world wide wibble. The port developed by Jeffrey Lee is a breakthrough for the shared-source project because it has ported the OS without an army of engineers.}}</ref><ref name="RISC OS Open wiki Cortex-A8 port status">{{cite web |url=https://www.riscosopen.org/wiki/documentation/pages/Cortex-A8+port+status/versions/1 |title=Cortex-A8 port status |access-date=31 January 2011 |publisher=[[RISC OS Open]] |quote=[The port includes] a modified version of the RISC OS kernel containing support for (all) Cortex-A8 CPU cores. |archive-date=26 October 2021 |archive-url=https://web.archive.org/web/20211026212426/https://www.riscosopen.org/hub/account/login |url-status=live }}</ref>{{Efn|(such as that used in the [[BeagleBoard]] and [[Touch Book]])}} and [[Cortex-A9]] processors<ref name="ROOL news 2015-04-25">{{cite web |url =https://www.riscosopen.org/news/articles/2015/04/25/risc-os-5-22-stable-is-now-available |title=RISC OS 5.22 stable is now available |access-date=25 April 2015 |last=Revill |first=Steve |date=25 April 2015 |publisher=[[RISC OS Open]]}}</ref>{{Efn|(such as that used in the [[PandaBoard]])}} and the low-cost educational [[Raspberry Pi]] series of computers, with the exception of the Raspberry Pi 5.<ref name="iconbar newsround">{{cite web |url=http://www.iconbar.com/articles/Newsround/index1271.html |title=Newsround |work=[[The Icon Bar]] |access-date=17 October 2011 |last=Lee |first=Jeffrey |archive-date=4 January 2016 |archive-url=https://web.archive.org/web/20160104182418/http://www.iconbar.com/articles/Newsround/index1271.html |url-status=live }}</ref><ref name="osnews risc os">{{cite web |url=http://www.osnews.com/story/25276/Raspberry_Pi_To_Embrace_RISC_OS |title=Raspberry Pi To Embrace RISC OS |work=[[OSNews]] |date=31 October 2011 |access-date=1 November 2011 |last=Holwerda |first=Thom |archive-date=4 January 2016 |archive-url=https://web.archive.org/web/20160104182418/http://www.osnews.com/story/25276/Raspberry_Pi_To_Embrace_RISC_OS |url-status=live }}</ref><ref name="archive london show 2011">{{cite news |title=The London show 2011 |work=[[Archive (magazine)|Archive]] |date=December 2011 |last=Dewhurst |first=Christopher |volume=23 |issue=3 |page=3}}</ref>

== History ==
{{Main|History of RISC OS}}
[[File:Riscos logo generic cogwheel richard hallas lg cogwheel x1.svg|thumb|110x110px|Original cogwheel logo]]
The first version of RISC OS was originally released in 1987 as ''Arthur 1.20''. The next version, {{nowrap|Arthur 2}}, became {{nowrap|RISC OS 2}} and was released in April 1989. RISC OS 3.00 was released with the A5000 in 1991, and contained many new features. By 1996, RISC OS had been shipped on over 500,000 systems.<ref>{{cite web|url=http://acorn.chriswhy.co.uk/docs/Acorn/ART/ART_DS013_AcornRISCOS.pdf|title=ART – Acorn RISC OS|work=acorn.chriswhy.co.uk|access-date=8 July 2011|archive-date=27 May 2013|archive-url=https://web.archive.org/web/20130527220851/http://acorn.chriswhy.co.uk/docs/Acorn/ART/ART_DS013_AcornRISCOS.pdf|url-status=live}}</ref>
[[File:Acorn Archimedes A3020 ( Bletchley Park, translucent ).png|thumb|An Acorn Archimedes A3020 computer running RISC OS]]
Acorn officially halted work on the OS in January 1999, renaming themselves [[Element 14 (company)|Element 14]]. In March 1999 a new company, [[RISCOS Ltd]], licensed the rights to develop a desktop version of RISC OS from Element 14, and continued the development of RISC OS 3.8, releasing it as ''RISC OS 4'' in July 1999. Meanwhile, Element 14 had also kept a copy of RISC OS 3.8 in house, which they developed into [[NCOS]] for use in [[set-top box]]es. In 2000, as part of the acquisition of Acorn Group plc by MSDW Investment, RISC OS was sold to [[Pace plc|Pace Micro Technology]],<ref name="register19990429">{{ cite news | url=https://www.theregister.com/1999/04/29/arm_denies_role_in_acorn/ | title=ARM denies role in Acorn dismemberment | work=[[The Register]] | date=24 April 1999 | access-date=31 January 2021 | last1=Cullen | first1=Drew }}</ref> who later sold it to [[Castle Technology]] Ltd.

In May 2001, RISCOS Ltd launched ''RISC OS Select'', a subscription scheme allowing users access to the latest RISC OS 4 updates. These upgrades are released as soft-loadable [[ROM image]]s, separate to the ROM where the boot OS is stored, and are loaded at boot time. Select 1 was shipped in May 2002, with Select 2 following in November 2002 and the final release of Select 3 in June 2004. In the same month, RISC OS 4.39, dubbed ''RISC OS Adjust'', was released. RISC OS Adjust was a culmination of all the Select Scheme updates to date, released as a physical set of replaceable ROMs for the RiscPC and A7000 series of machines.

Meanwhile, in October 2002, [[Castle Technology]] released the ''Acorn clone'' [[Iyonix PC]]. This ran a [[32-bit computing|32-bit]] (in contrast to [[26-bit computing|26-bit]]) variant of RISC OS, named ''RISC OS 5''. RISC OS 5 is a separate evolution of RISC OS based upon the [[NCOS]] work done by Pace. The following year, Castle Technology bought RISC OS from Pace for an undisclosed sum. In October 2006, Castle announced a [[Source-available software|shared source]] license plan, managed by [[RISC OS Open Limited]], for elements of ''RISC OS 5''.

In October 2018, RISC OS 5 was re-licensed under the [[Apache 2.0]] license.<ref>{{Cite news|url=https://www.theregister.com/2018/10/23/risc_os_open_source/|title=Roughly 30 years after its birth at UK's Acorn Computers, RISC OS 5 is going open source|first=Richard|last=Speed|work=[[The Register]]|access-date=26 October 2021|archive-date=23 September 2021|archive-url=https://web.archive.org/web/20210923185001/https://www.theregister.com/2018/10/23/risc_os_open_source/|url-status=live}}</ref>

In 2018 [[RISC OS Developments]] acquired Castle Technology Ltd including its intellectual property.<ref name="riscosdev">{{cite web |url=https://www.riscosdev.com/ |title=Home |website=riscosdev.com}}</ref>

In December 2020, the source code of RISC OS 3.71 was leaked to The Pirate Bay.{{cn|date=May 2022}}
{{clear}}

== Features ==
=== OS core ===
The OS is [[single-user]] and employs [[cooperative multitasking]] (CMT).<ref name="byte tired">{{cite journal |url=https://archive.org/details/eu_BYTE-1996-12_OCR/page/n84/mode/1up |title=A RISC OS for All Seasons |last=Palmer |first=Stewart |journal=[[Byte (magazine)|Byte]] |date=December 1996 |volume=21 |issue=12 |page=49 |oclc=208951251 |issn=0360-5280}}</ref> While most current desktop OSes use [[preemption (computing)|preemptive]] [[computer multitasking|multitasking]] (PMT) and [[thread (computer science)|multithreading]], {{nowrap|RISC OS}} remains with a CMT system. By 2003, many users had called for the OS to migrate to PMT.<ref name="drobe williams pmt 2003">{{cite news|last=Williams|first=Chris|title=Imagining RISC OS and PMT|url=http://www.drobe.co.uk/article.php?id=764|access-date=10 July 2012|newspaper=[[Drobe]]|date=26 July 2003|archive-date=17 June 2018|archive-url=https://web.archive.org/web/20180617115807/http://www.drobe.co.uk/article.php?id=764|url-status=live}}</ref> The OS [[memory protection]] is not comprehensive.<ref>Michael Reed [https://books.google.com/books?id=Lr8ldHhh_wsC&pg=PA82 ''Tech Book 1'' – Published articles Oct 2006 – June 2008] {{Webarchive|url=https://web.archive.org/web/20200726094727/https://books.google.es/books?id=Lr8ldHhh_wsC&pg=PA82 |date=26 July 2020 }}</ref><ref>{{cite web|url=http://www.drobe.co.uk/riscos/artifact1327.html|title=RISC OS Memory Protection|website=Drobe: The Archives|access-date=4 March 2013|archive-date=31 March 2014|archive-url=https://web.archive.org/web/20140331035623/http://www.drobe.co.uk/riscos/artifact1327.html|url-status=live}}</ref>

The core of the OS is stored in [[read-only memory|ROM]], giving a fast [[bootup]] time and safety from operating system corruption. RISC OS 4 and 5 are stored in {{nowrap|4 MB}} of [[flash memory]], or as a [[ROM image]] on [[SD card]] on single board computers such as the Beagleboard or Raspberry Pi, allowing the operating system to be updated without having to replace the ROM chip. The OS is made up of several [[Loadable kernel module|module]]s. These can be added to and replaced, including soft-loading of modules not present in ROM at run time and on-the-fly replacement. This design has led to OS developers releasing rolling updates to their versions of the OS, while third parties are able to write OS replacement modules to add new features. OS modules are accessed via software interrupts (SWIs), similar to [[system call]]s in other operating systems.

Most of the OS has defined [[application binary interface]]s (ABIs) to handle filters and vectors. The OS provides many ways in which a program can intercept and modify its operation. This simplifies the task of modifying its behaviour, either in the GUI, or deeper. As a result, there are several third-party programs which allow customising the OS look and feel.

=== File system ===
{{More citations needed section|date=July 2017}}
The [[file system]] is volume-oriented: the top level of the file hierarchy is a volume (disc, network share) prefixed by the file system type. To determine [[file type]], the OS uses [[metadata]] instead of [[file extension]]s. Colons are used to separate the file system from the rest of the path; the root is represented by a dollar (<code>$</code>) sign and directories are separated by a full stop (<code>.</code>). Extensions from foreign file systems are shown using a slash (<code>example.txt</code> becomes <code>example/txt</code>).<ref name="drobe naulls 2004">{{cite web |url=http://www.drobe.co.uk/article.php?id=921 |title=RISC OS filename translation |work=[[Drobe]] |date=2 January 2004 |access-date=25 April 2012 |last=Naulls |first=Peter |archive-date=9 July 2011 |archive-url=https://web.archive.org/web/20110709035738/http://www.drobe.co.uk/article.php?id=921 |url-status=live }}</ref> For example, <code>ADFS::HardDisc4.$</code> is the root of the disc named ''HardDisc4'' using the [[Advanced Disc Filing System]] (ADFS) file system. {{nowrap|RISC OS}} filetypes can be preserved on other systems by appending the hexadecimal type as '<code>,xxx</code>' to filenames.<ref name="drobe naulls 2004" /><ref name="osnews round 2004">{{cite web|url=http://www.osnews.com/story/6170/Emulating_RISC_OS_under_Windows/page3/|title=Emulating RISC OS, Page 3/3|website=[[OSNews]]|access-date=25 April 2012|archive-date=13 March 2012|archive-url=https://web.archive.org/web/20120313042944/http://www.osnews.com/story/6170/Emulating_RISC_OS_under_Windows/page3/|url-status=live}}</ref> When using [[cross-platform]] software, filetypes can be invoked on other systems by naming appending '<code>/[extension]</code>' to the filename under {{nowrap|RISC OS}}.<ref name="archive fitton 1994">{{citation |last=Fitton |first=Gerald |date=August 1994 |title=Fireworkz for Windows |periodical=[[Archive (magazine)|Archive]] |publisher=Abbey Press |location=Glastonbury |volume=7 |issue=11 |page=21 |url=http://downloads.abacusline.me.uk/pdf/Arc/2007/GC0701.pdf |oclc=222434223 |access-date=25 April 2012 |archive-date=3 December 2013 |archive-url=https://web.archive.org/web/20131203024536/http://downloads.abacusline.me.uk/pdf/Arc/2007/GC0701.pdf |url-status=live }}</ref>

A file system can present a file of a given type as a volume of its own, similar to a [[loop device]]. The OS refers to this function as an image filing system. This allows transparent handling of archives and similar files, which appear as directories with some special properties. Files inside the image file appear in the hierarchy underneath the parent archive. It is not necessary for the archive to contain the data it refers to: some symbolic link and network share file systems put a reference inside the image file and go elsewhere for the data.

The file system abstraction layer [[Application programming interface|API]] uses 32-bit file offsets, making the largest single file 4&nbsp;[[Gibibyte|GiB]] (minus 1 byte) long. However, prior to RISC OS 5.20 the file system abstraction layer and many RISC OS-native file systems limited support to 31&nbsp;bits (just under 2&nbsp;GiB) to avoid dealing with apparently negative file extents when expressed in [[two's complement]] notation.{{citation needed|date=July 2017}}

=== File formats ===
{{Main|List of RISC OS filetypes}}
The OS uses [[metadata]] to distinguish [[file format]]s. Some [[list of file formats|common file formats]] from other systems are mapped to filetypes by the MimeMap module.<ref name="iyonix">{{cite web|url=http://www.iyonix.com/32bit/MIMEMap.shtml|title=Iyonix: MIMEMap|work=iyonix.com|url-status=dead|archive-url=https://web.archive.org/web/20160303223854/http://www.iyonix.com/32bit/MIMEMap.shtml|archive-date=3 March 2016}}</ref>

=== Kernel ===
The RISC OS kernel is single-tasking and controls handling of [[interrupt]]s, [[Direct memory access|DMA]] services, memory allocation and the video display; the cooperative multi-tasking is provided by the WindowManager module.<ref name="byte tired" />

=== Desktop ===
[[File:RISCOS 4 scr.png|thumb|A screenshot of RISC OS 4]]
The [[WIMP (computing)|WIMP]] interface is based on a [[stacking window manager]] and incorporates three [[mouse button]]s<ref name="Ryan2011">{{cite book|last=Ryan|first=Dan|title=History of Computer Graphics: DLR Associates Series|url=https://books.google.com/books?id=136myWlKpwEC&pg=PA358|access-date=13 June 2013|date=13 April 2011|publisher=AuthorHouse|isbn=978-1-4567-5115-9|page=358|archive-date=6 July 2014|archive-url=https://web.archive.org/web/20140706155034/http://books.google.com/books?id=136myWlKpwEC&pg=PA358|url-status=live}}</ref> (named ''Select'', ''Menu'' and ''Adjust''), [[context-sensitive user interface|context-sensitive]] menus, window order control (i.e. send to back) and dynamic window [[Focus (computing)|focus]] (a window can have input focus at any position on the stack). The [[icon bar]] ([[Dock (computing)|Dock]]) holds icons which represent mounted disc drives, RAM discs, running applications, system utilities and docked: files, directories or inactive applications. These icons have context-sensitive menus and support [[drag-and-drop]] operation. They represent the running application as a whole, irrespective of whether it has open windows.

The GUI functions on the concept of files. The Filer, a [[spatial file manager]], displays the contents of a disc. Applications are run from the Filer view and files can be dragged to the Filer view from applications to perform saves, rather than opening a separate 'Save' dialog box where the user must navigate to a location already visible in the Finder. In addition, files can be directly transferred between applications by dragging a save icon into another application's window.

[[Application directories]] are used to store applications. The OS differentiates them from normal directories through the use of an [[Exclamation mark#Computing|exclamation mark]] (also called a ''pling'' or ''shriek'') prefix. Double-clicking on such a directory launches the application rather than opening the directory. The application's executable files and resources are contained within the directory, but normally they remain hidden from the user. Because applications are self-contained, this allows drag-and-drop installing and removing.

The {{nowrap|RISC OS}} ''Style Guide'' encourages a consistent [[look and feel]] across applications. This was introduced in {{nowrap|RISC OS 3}} and specifies application appearance and behaviour. Acorn's own main [[#Bundled applications|bundled applications]] were not updated to comply with the guide until {{nowraplinks|[[RISCOS Ltd]]}}'s ''Select'' release in 2001.<ref name="iconbar possibly influential">{{cite web |url=http://www.iconbar.com/articles/Influential/index1152.html |title=An arbitrary number of possibly influential RISC OS things |work=[[The Icon Bar]] |date=23 March 2007 |access-date=27 September 2011 |last=Phil |first=Mellor |quote=Admittedly it wasn't until RISC OS Select was released, almost 10 years later, that the standard Acorn applications (Draw, Edit, and Paint) implemented the style guide's clipboard recommendations, but most products followed it with care. |archive-date=31 March 2012 |archive-url=https://web.archive.org/web/20120331173614/http://www.iconbar.com/articles/Influential/index1152.html |url-status=live }}</ref>

=== Font manager ===
RISC OS was the first operating system to provide scalable anti-aliased fonts.<ref>{{cite web |url=http://www.osnews.com/story/6170/Emulating_RISC_OS_under_Windows/page1/ |title=Emulating RISC OS under Windows |access-date=12 May 2011 |last=Round |first=Mark |date=26 February 2004 |work=OSnews |quote=Many of the UI concepts that we take for granted were first pioneered in RISC OS, for instance: scalable anti-aliased fonts and an operating system extendable by 'modules', while most of the PC world was still on Windows 3.0. |archive-date=14 November 2010 |archive-url=https://web.archive.org/web/20101114004250/http://www.osnews.com/story/6170/Emulating_RISC_OS_under_Windows/page1/ |url-status=live }}</ref><ref>{{cite web |url=http://telcontar.net/Misc/GUI/RISCOS/ |title=The RISC OS GUI |access-date=12 May 2011 |last=Ghiraddje |date=22 December 2009 |publisher=Telcontar.net |quote=Only with Mac OS X did any mainstream graphical interface provide the smoothly rendered, fractionally spaced type that Acorn accomplished in 1992 or earlier. |archive-date=16 July 2011 |archive-url=https://web.archive.org/web/20110716233538/http://telcontar.net/Misc/GUI/RISCOS/ |url-status=live }}</ref><ref>{{cite web |url=https://arstechnica.com/old/content/2005/05/gui.ars/6 |title=A History of the GUI |access-date=25 May 2011 |first=Jeremy |last=Reimer |date=May 2005 |publisher=[[ArsTechnica]] |quote=[...] in 1987, the UK-based company Acorn Computers introduced their [...] GUI, called "Arthur", also was the first to feature anti-aliased display of on-screen fonts, even in 16-color mode! |archive-date=2 December 2011 |archive-url=https://web.archive.org/web/20111202061840/http://arstechnica.com/old/content/2005/05/gui.ars/6 |url-status=live }}</ref><ref>{{cite web |url=http://www.osnews.com/story/21713/Screen_Fonts_Shape_Accuracy_or_On-Screen_Readability_ |title=Screen Fonts: Shape Accuracy or On-Screen Readability? |access-date=13 June 2011 |first=Thom |last=Holwerda |date=23 June 2005 |publisher=[[OSNews]] |quote=[...] it was RISC OS that had the first system-wide, intricate [...] font rendering in operating systems. |archive-date=19 November 2011 |archive-url=https://web.archive.org/web/20111119223926/http://www.osnews.com/story/21713/Screen_Fonts_Shape_Accuracy_or_On-Screen_Readability_ |url-status=live }}</ref> Anti-aliased fonts were already familiar from Arthur, and their presence in RISC OS was confirmed in an early 1989 preview,<ref name="PCW 1989-01">{{cite news | first1=Dick | last1=Pountain | title=Screentest: Archie RISC OS | work=[[Personal Computer World]] | date=January 1989 | url=http://chrisacorns.computinghistory.org.uk/docs/Mags/PCW/PCW_Jan89_RISCOS.pdf | page=154 | access-date=4 March 2021 | quote=[ArcDraw] can also add text in multiple sizes and fonts to a drawing (including anti-aliased fonts) | archive-date=13 June 2021 | archive-url=https://web.archive.org/web/20210613044349/http://chrisacorns.computinghistory.org.uk/docs/Mags/PCW/PCW_Jan89_RISCOS.pdf | url-status=live }}</ref> featuring in the final RISC OS 2 product, launched in April 1989.<ref name="acornuser198902">{{ cite news | url=https://archive.org/details/AcornUser079-Feb89/page/n10/mode/1up | title=RISC OS is ready for April launch | work=Acorn User | date=February 1989 | access-date=31 October 2020 | pages=9 }}</ref>

A new version of the font manager employing "new-style outline fonts" was made available after the release of RISC OS,<ref name="acornuser198904_fonts">{{ cite news | url=https://archive.org/details/AcornUser081-Apr89/page/n8/mode/1up | title=New fonts for DTP | work=Acorn User | date=April 1989 | access-date=3 May 2021 | pages=7 }}</ref> offering full support for the printing of scalable fonts, and was provided with Acorn Desktop Publisher.<ref name="acornuser198910">{{ cite news | url=https://archive.org/details/AcornUser087-Oct89/page/n135/mode/2up | title=Hold the Font Page | work=Acorn User | date=October 1989 | access-date=14 April 2021 | last1=Bell | first1=Graham | pages=134–135 }}</ref> It was also made available separately and bundled with other applications.<ref name="acornuser199004_font">{{ cite news | url=https://archive.org/details/AcornUser093-Apr90/page/n20/mode/1up | title=Acorn Customer Hotline | work=Acorn User | date=April 1990 | access-date=2 May 2021 | pages=19 }}</ref> This [[outline font]] manager provides support for the rendering of font outlines to bitmaps for screen and printer use, employing [[spatial anti-aliasing|anti-aliasing]] for on-screen fonts, utilising sub-pixel anti-aliasing and caching for small font sizes.<ref name="raine1991">{{ cite conference | url=https://archive.org/details/1989-proceedings-5th-comp-graphics-workshop/page/25/mode/1up | title=The Acorn Outline Font Manager | last1=Raine | first1=Neil | last2=Seal | first2=David | last3=Stoye | first3=William | last4=Wilson | first4=Roger | conference=Fifth Computer Graphics Workshop | location=Monterey, California | date=November 1989 | publisher=USENIX Association | pages=25–36 }}</ref> At the time of the introduction of Acorn's outline font manager, the developers of rival desktop systems were either contemplating or promising outline font support for still-unreleased products such as Macintosh [[System 7]] and [[OS/2]] version 2.<ref name="acornuser198911_mytype">{{ cite news | url=https://archive.org/details/AcornUser088-Nov89/page/n69/mode/2up | title=My Type | work=Acorn User | date=November 1989 | access-date=7 May 2021 | last1=Bell | first1=Graham | pages=68–69 }}</ref>

From 1993, starting with the German RISC OS 3.12, and in 1994 for RISC OS 3.5, it has been possible to use an outline anti-aliased font in the WindowManager for UI elements, rather than the [[Bitmap fonts|bitmap system font]] from previous versions.<ref>{{cite magazine
| date        = July 1993
| title       = Acorn signs pre-press deal
| url         = https://archive.org/details/AcornUser132-Jul93/page/n11/mode/2up
| magazine    = [[Acorn User]]
| page        = 10
| publisher   = [[Addison-Wesley]]
| access-date =
}}</ref><ref name="acorn_an253">{{ cite tech report | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/AN/253.pdf | title=Acorn Computers Support Group Application Notice 253 – New features of RISC OS version 3.5 | publisher=Acorn Computers Limited | last1=Murphy | first1=Dean | date=29 March 1994 | access-date=2 March 2022 | issue=0.02 }}</ref> RISC OS 4 does not support [[Unicode]] but "RISC OS 5 provides a Unicode Font Manager which is able to display Unicode characters and accept text in [[UTF-8]], UTF-16 and UTF-32. Other parts of the RISC OS kernel and core modules support text described in UTF-8."<ref>{{cite web|url=http://www.riscos.info/index.php/Unicode_in_RISC_OS|title=Unicode in RISC OS|work=riscos.info|access-date=28 April 2015|archive-date=11 April 2015|archive-url=https://web.archive.org/web/20150411221409/http://www.riscos.info/index.php/Unicode_in_RISC_OS|url-status=live}}</ref><!--

There are two issues:         
                                                                                                                                  
1) Printing Unicode to a PostScript printer will break as PDriverPS just
   embeds the Fonts:Encodings.UTF8 encoding file directly in the PS             
   output. This file is not valid PostScript.                                   
                                                                                
2) Printing UTF-16 or UTF-32 to any printer driver will fail as they're         
   not expecting anything other than an 8-bit encoding.[..]

Issue 1 can be avoided by using the PostScript 3 printer driver (instead of using the native RISC OS PostScript printer driver) which was developed by John Tytgat and Martin Würthner. The ROOL project has released updated Printer Manager software which fixes issue 2.-->

Support for the characters of RISC OS (and some other historic computers) was added to [[Unicode]] 13.0 (in 2020).<ref>{{Cite web|url=https://www.unicode.org/versions/Unicode13.0.0/ch22.pdf|title=The Unicode® Standard Version 13.0 – Core Specification|access-date=11 March 2020|archive-date=6 May 2021|archive-url=https://web.archive.org/web/20210506122306/https://www.unicode.org/versions/Unicode13.0.0/ch22.pdf|url-status=live}}</ref>

=== Bundled applications ===
{{Main|List of RISC OS bundled applications}}
{{nowrap|RISC OS}} is available in several distributions, all of which include a small standard set of [[desktop application]]s, but some of which also include a much wider set of useful programs. Some of those richer distributions are freely available, some are paid for.

== Backward compatibility ==
Limited [[software portability]] exists with subsequent versions of the OS and hardware. Single-tasking [[BBC BASIC]] applications often require only trivial changes, if any.{{citation needed|date=June 2012}} Successive OS upgrades have raised more serious issues of [[backward compatibility]] for desktop applications and games.<ref>{{cite web|title=ARM architecture versions cheat sheet|url=http://www.starfighter.acornarcade.com/mysite/articles/armv.html|access-date=14 January 2015|archive-date=12 April 2015|archive-url=https://web.archive.org/web/20150412223011/http://www.starfighter.acornarcade.com/mysite/articles/armv.html|url-status=live}}</ref> Applications still being maintained by their author(s) or others have sometimes historically been amended to provide compatibility.{{citation needed|date=June 2012}}

The introduction of the [[RiscPC]] in 1994 and its later [[StrongARM]] upgrade raised issues of incompatible code sequences and proprietary squeezing ([[data compression]]). [[Patch (computing)|Patch]]ing of applications for the StrongARM was facilitated and Acorn's ''UnsqueezeAIF'' software unsqueezed images according to their [[AIF header]].<ref name="riscos an 295 1996">{{cite web|title=Application Note 295|url=http://acorn.riscos.com/riscos3/37/37DiscImage/Manuals/AppNote|work=Engineering Support Application Note|publisher=[[Acorn Computers]]|access-date=28 June 2012|date=4 October 1996|url-status=dead|archive-url=https://archive.today/20130104150342/http://acorn.riscos.com/riscos3/37/37DiscImage/Manuals/AppNote|archive-date=4 January 2013}}</ref> The incompatibilities prompted release by ''The ARM Club'' of its ''Game On!''<ref name="acornarcade foggy 2001">{{cite news|author=Foggy|title=Games FAQ|url=http://acornarcade.com/articles/Games_FAQ/index1004.html|access-date=27 June 2012|newspaper=[[Acorn Arcade]]|date=11 July 2001|archive-date=21 March 2012|archive-url=https://web.archive.org/web/20120321065412/http://www.acornarcade.com/articles/Games_FAQ/index1004.html|url-status=live}}</ref><ref name="armclub 2001">{{cite web|title=Game On!|last=Ruck|first=David J.|website=The ARM Club: Software Products|publisher=David J. Ruck|url=http://www.armclub.org.uk/products/gameon/|archive-url=https://web.archive.org/web/20011004235759/http://www.armclub.org.uk/products/gameon/|archive-date=4 October 2001|access-date=27 June 2012}}</ref> and ''StrongGuard'' software.<ref name="acornarcade foggy 2001" /><ref name="armclub 2009">{{cite web|title=StrongGuard|url=http://www.armclub.org.uk/products/strongguard/|last=Ruck|first=David J.|website=The ARM Club: Software Products|publisher=David J. Ruck|archive-url=https://web.archive.org/web/20090212202624/http://www.armclub.org.uk/products/strongguard/|archive-date=12 February 2009|access-date=27 June 2012}}</ref><ref name="acornarcade mckillop 2000">{{cite news|last=McKillop|first=Keith|title=RISC OS 2000: Show Report|url=http://acornarcade.com/RISC_OS_2000_Show_Report/news971.html|access-date=27 June 2012|newspaper=[[Acorn Arcade]]|date=22 November 2000|archive-date=16 October 2015|archive-url=https://web.archive.org/web/20151016230129/http://acornarcade.com/RISC_OS_2000_Show_Report/news971.html|url-status=live}}</ref> They allowed some formerly incompatible software to run on new and upgraded systems. The version of the OS for the [[A9home]] prevented the running of software without an AIF header (in accord with Application Note 295)<ref name="riscos 2006">{{cite web|url=http://www.riscos.com/news/news_items/NewsMay2006.pdf|archive-url=https://www.webcitation.org/6BwhJRm1b?url=http://www.riscos.com/news/news_items/NewsMay2006.pdf|url-status=dead|archive-date=5 November 2012|title=RISCOS Ltd News|publisher=[[RISCOS Ltd]]|access-date=28 June 2012|date=May 2006}}</ref> to stop "trashing the desktop".<ref name="drobe williams 2006">{{cite news|last=Williams|first=Chris|title=ROL release C99 SCL to A9home users|url=http://www.drobe.co.uk/article.php?id=1580|access-date=28 June 2012|newspaper=[[Drobe]]|date=17 April 2006|archive-date=1 October 2009|archive-url=https://web.archive.org/web/20091001162532/http://www.drobe.co.uk/article.php?id=1580|url-status=live}}</ref>

The [[Iyonix PC]] ({{nowrap|RISC OS 5}}) and [[A9home]] (custom {{nowrap|RISC OS 4}}) saw further software incompatibility because of the deprecated {{nowrap|[[26-bit computing|26-bit]]}} addressing modes. Most applications under active development have since been rewritten.<ref name="riscworld thompson v7i2">{{cite news|last=Thompson|first=Matt|title=Iyonix Issues|url=http://www.apdl.co.uk/riscworld/volume7/issue2/iyonix/|access-date=27 June 2012|volume=7|issue=2|newspaper=RISC World}}</ref><ref name="riscworld thompson v8i2">{{cite news|last=Thompson|first=Matt|title=Iyonix Issues|url=http://www.apdl.co.uk/riscworld/volume8/issue2/iyonix/|access-date=27 June 2012|volume=8|issue=2|newspaper=RISC World}}</ref><ref name="wrocc versions">{{cite web|title=A Guide to RISC OS Versions|url=http://www.wrocc.org.uk/riscos/versions.shtml|work=WROCC website|publisher=Wakefield RISC OS Computer Club|access-date=27 June 2012|archive-date=7 January 2013|archive-url=https://web.archive.org/web/20130107011934/http://www.wrocc.org.uk/riscos/versions.shtml|url-status=live}}</ref> [[Static code analysis]] to detect {{nowrap|26-bit}}-only sequences can be undertaken using ''ARMalyser''.<ref name="riscworld brett v7i1">{{cite news|last=Brett|first=Paul|title=PD World|url=http://www.apdl.co.uk/riscworld/volume7/issue1/pd/|access-date=27 June 2012|newspaper=RISC World|volume=7|issue=1}}</ref> Its output can be helpful in making 32-bit versions of older applications for which the source code is unavailable.<ref name="riscworld brett v3i1">{{cite news|last=Brett|first=Paul|title=PD World|url=http://www.apdl.co.uk/riscworld/volume3/issue1/pd/|access-date=27 June 2012|newspaper=RISC World|volume=3|issue=1}}</ref><ref name="riscworld brett v7i1" /><ref name=armclub>{{cite web|title=Free Software|url=http://www.armclub.org.uk/free/|last=Ruck|first=David J.|website=The ARM Club|publisher=David J. Ruck|access-date=27 June 2012|archive-date=26 June 2012|archive-url=https://web.archive.org/web/20120626180450/http://www.armclub.org.uk/free/|url-status=live}}</ref> Some older 26-bit software can be run without modification using the [[Aemulor]] emulator.<ref name="wrocc versions" /><ref name="drobe williams 2002" /><ref name="drobe williams 2003" />

Additional incompatibilities were introduced with newer [[ARM core]]s, such as ARMv7 in the [[BeagleBoard]] and ARMv8 in the {{nowrap|[[Raspberry Pi 3]]}}. This includes changes to unaligned memory access in ARMv6/v7 and removal of the SWP instructions in ARMv8.<ref>{{Cite web |url=https://www.riscosopen.org/wiki/documentation/show/ARMv7%20compatibility%20primer#TOC3.11 |title=ARMv7 compatibility primer in Documentation<!-- Bot generated title --> |access-date=16 October 2021 |archive-date=16 October 2021 |archive-url=https://web.archive.org/web/20211016142701/https://www.riscosopen.org/wiki/documentation/show/ARMv7%20compatibility%20primer#TOC3.11 |url-status=live }}</ref>

== Supported hardware ==
RISC OS has also been used by both Acorn and [[Pace Micro Technology]] in various TV connected [[set-top box]]es, sometimes referred to instead as [[NCOS]].{{Citation needed|date=December 2024}} A special cut down RISC OS Pico (for 16MiB cards and larger) styled to start up like a [[BBC Micro]] was released for [[BASIC|BASIC's]] 50th anniversary.<ref>{{cite web |date=5 January 2014 |title=Happy birthday, BASIC |url=https://www.riscosopen.org/news/articles/2014/05/01/happy-birthday-basic |url-status=live |archive-url=https://web.archive.org/web/20181109020010/https://www.riscosopen.org/news/articles/2014/05/01/happy-birthday-basic |archive-date=9 November 2018 |access-date=8 May 2018}}</ref> [[SD card]] images have been released for downloading free of charge to [[Raspberry Pi]] 1, 2, 3, & 4 users with a full [[graphical user interface]] (GUI) version<ref>{{cite web |title=Downloads |url=http://www.raspberrypi.org/downloads |url-status=live |archive-url=https://web.archive.org/web/20130114192342/http://www.raspberrypi.org/downloads |archive-date=14 January 2013 |access-date=2 September 2013 |publisher=Raspberry Pi}}</ref> and a [[command-line interface]] only version (RISC OS Pico, at 3.8&nbsp;MB).<ref name="Pico">{{cite web |title=RISC OS Open: Raspberry Pi |url=https://www.riscosopen.org/content/downloads/raspberry-pi |url-status=live |archive-url=https://web.archive.org/web/20210320161349/https://www.riscosopen.org/content/downloads/raspberry-pi |archive-date=20 March 2021 |access-date=25 April 2015 |work=riscosopen.org}}</ref>

Versions of RISC OS run or have run on the following hardware: ([[RISC OS Open Limited]] adopted<ref name="Stable release criteria">{{cite web |date=12 January 2017 |title=Stable release criteria |url=https://www.riscosopen.org/content/documents/stable-releases |url-status=live |archive-url=https://web.archive.org/web/20181109020018/https://www.riscosopen.org/content/documents/stable-releases |archive-date=9 November 2018 |access-date=12 January 2017}}</ref> the '[[Software versioning#Odd-numbered versions for development releases|even numbers are stable]]' version numbering scheme post version 5.14, hence some table entries above include two latest releases – the last stable one and the more recent development one.)

{| class="wikitable"
|+ RISC OS compatible hardware
! rowspan="2" style="vertical-align:bottom;" |Machine !! rowspan="2" style="vertical-align:bottom;" |[[Arm architecture|ARM architecture]] !! rowspan="2" style="vertical-align:bottom;" |Introduced !! colspan="2" style="vertical-align:bottom;" |[[Acorn Computers|Acorn]] version !! colspan="2" style="vertical-align:bottom;" |[[RISCOS Ltd]] version !! colspan="2" style="vertical-align:bottom;" |[[Castle Technology]], [[RISC OS Open]] version
|-
! First !! Last !! First !! Last !! First !! Latest
|-
| colspan="8" | '''ARM with [[26-bit computing|26-bit]] program counter'''
|-
| [[Acorn Archimedes]] || ARMv2 || 1987–1992 || 0.20 || 3.1x || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}}
|-
| colspan="8" | '''ARM with 26- & 32-bit program counter'''
|-
| [[Risc PC|Acorn Risc PC]] || ARMv3 / v4 || 1994<ref name="riscpc">{{Cite web |title=Chris's Acorns: Risc PC Computers |url=http://chrisacorns.computinghistory.org.uk/Computers/RiscPCComputers.html |url-status=live |archive-url=https://web.archive.org/web/20171021213428/http://chrisacorns.computinghistory.org.uk/Computers/RiscPCComputers.html |archive-date=21 October 2017 |access-date=22 July 2015 |website=chrisacorns.computinghistory.org.uk}}</ref> || 3.50<ref name="riscpc" /> || rowspan="2" | 3.71 || rowspan="2" | 4.00 || rowspan="2" | 6.20<ref name="select-faq">{{cite web |title=RISC OS Six Frequently Asked Questions |url=http://select.riscos.com/RISCOS6/faq.html |archive-url=https://archive.today/20121208135752/http://select.riscos.com/RISCOS6/faq.html |archive-date=8 December 2012}}</ref> || rowspan="2" | 5.15 || rowspan="2" | 5.30<ref name="downloads/riscpc">{{Cite web |title=RISC OS Open: RiscPC |url=https://www.riscosopen.org/content/downloads/riscpc |url-status=live |archive-url=https://web.archive.org/web/20150411175939/https://www.riscosopen.org/content/downloads/riscpc |archive-date=11 April 2015 |access-date=25 April 2015 |website=www.riscosopen.org}}</ref>/5.31
|-
| [[Acorn A7000|Acorn A7000 and A7000+]] || ARMv3 || 1995<ref name="a7000">{{cite web |title=Chris's Acorns: Acorn A7000 |url=http://chrisacorns.computinghistory.org.uk/Computers/A7000.html |url-status=live |archive-url=https://web.archive.org/web/20151011194352/http://chrisacorns.computinghistory.org.uk/Computers/A7000.html |archive-date=11 October 2015 |access-date=22 July 2015 |work=computinghistory.org.uk}}</ref>{{spaced ndash}}1997<ref name="a7000+">{{cite web |title=Chris's Acorns: Acorn A7000+ |url=http://chrisacorns.computinghistory.org.uk/Computers/A7000+.html |url-status=live |archive-url=https://web.archive.org/web/20151011194330/http://chrisacorns.computinghistory.org.uk/Computers/A7000+.html |archive-date=11 October 2015 |access-date=22 July 2015 |work=computinghistory.org.uk}}</ref> || 3.60<ref name="a7000" /><ref name="a7000+" /> 
|-
| [[Acorn Phoebe]] (cancelled) || ARMv4 || 1998 || 3.80 (Ursula) || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}}
|-
| MicroDigital Medi<ref>repackaged A7000+</ref> || rowspan="3" | ARMv3 || 1998<ref name="medi">{{cite web |title=Chris's Acorns: MicroDigital |url=http://chrisacorns.computinghistory.org.uk/AfterAcorn/Microdigital.html#Medi |url-status=live |archive-url=https://web.archive.org/web/20150722224655/http://chrisacorns.computinghistory.org.uk/AfterAcorn/Microdigital.html#Medi |archive-date=22 July 2015 |access-date=22 July 2015 |work=computinghistory.org.uk}}</ref> || 3.71<ref name="medi" /> || {{n/a}} || 4.02 || 6.20 || {{n/a}} || {{n/a}}
|-
| MicroDigital Mico || 1999<ref name="mico">{{cite web |title=Chris's Acorns: MicroDigital |url=http://chrisacorns.computinghistory.org.uk/AfterAcorn/Microdigital.html#Mico |url-status=live |archive-url=https://web.archive.org/web/20150722224655/http://chrisacorns.computinghistory.org.uk/AfterAcorn/Microdigital.html#Mico |archive-date=22 July 2015 |access-date=22 July 2015 |work=computinghistory.org.uk}}</ref> || {{n/a}} || {{n/a}} || 4.03<ref name="mico" /> ||4.39<ref name="select-faq" /> || {{n/a}} || {{n/a}}
|-
| RiscStation R7500 || 1999<ref name="r7500">{{cite web |title=Chris's Acorns: RISC OS After Acorn |url=http://chrisacorns.computinghistory.org.uk/AfterAcorn.html#RiscStation |url-status=live |archive-url=https://web.archive.org/web/20151011194254/http://chrisacorns.computinghistory.org.uk/AfterAcorn.html#RiscStation |archive-date=11 October 2015 |access-date=22 July 2015 |work=computinghistory.org.uk}}</ref> || {{n/a}} || {{n/a}} || 4.03<ref name="r7500" /> ||4.39<ref name="select-faq" /> || {{n/a}} || {{n/a}}
|-
| Castle Kinetic RiscPC || rowspan="2" | ARMv4 || 2000<ref name="kinetic">{{cite web |title=The Icon Bar: Castle reveal Kinetic to the press |url=http://www.iconbar.com/forums/viewthread.php?newsid=918 |url-status=live |archive-url=https://web.archive.org/web/20120716211137/http://www.iconbar.com/forums/viewthread.php?newsid=918 |archive-date=16 July 2012 |access-date=23 February 2011 |work=iconbar.com}}</ref> || {{n/a}} || {{n/a}} || 4.03 || 6.20 || 5.19<ref name="ROOLkinetic">{{cite web |date=28 March 2013 |title=Bugs and sources |url=https://www.riscosopen.org/viewer/revisions/logs?ident=1364507316-018164.html |url-status=live |archive-url=https://web.archive.org/web/20150413035910/https://www.riscosopen.org/viewer/revisions/logs?ident=1364507316-018164.html |archive-date=13 April 2015 |access-date=2 September 2013 |publisher=RISC OS Open}}</ref> || 5.30<ref name="downloads/riscpc" />/5.31
|-
| [[MicroDigital Omega]] || 2003<ref>{{cite web |title=Omega production saga continues – Drobe.co.uk archives |url=http://www.drobe.co.uk/article.php?id=973 |url-status=live |archive-url=https://web.archive.org/web/20120316220842/http://www.drobe.co.uk/article.php?id=973 |archive-date=16 March 2012 |access-date=8 February 2012 |work=drobe.co.uk}}</ref> || {{n/a}} || {{n/a}} || 4.03<ref name="omega">{{cite web |title=Chris's Acorns: MicroDigital |url=http://chrisacorns.computinghistory.org.uk/AfterAcorn/Microdigital.html#Omega |url-status=live |archive-url=https://web.archive.org/web/20150722224655/http://chrisacorns.computinghistory.org.uk/AfterAcorn/Microdigital.html#Omega |archive-date=22 July 2015 |access-date=22 July 2015 |work=computinghistory.org.uk}}</ref> || 4.39<ref name="select-faq" /> || {{n/a}} || {{n/a}}
|-
| Advantage Six A75 || ARMv3 || 2004<ref>{{cite web |title=A75 is ARM7500FE ruggable – Drobe.co.uk archives |url=http://www.drobe.co.uk/article.php?id=1047 |url-status=live |archive-url=https://web.archive.org/web/20151016230127/http://www.drobe.co.uk/article.php?id=1047 |archive-date=16 October 2015 |access-date=8 February 2012 |work=drobe.co.uk}}</ref> || {{n/a}} || {{n/a}} ||4.39<ref>{{cite web |title=Advantage6: Thea75 |url=http://www.advantagesix.com/Thea75.html |url-status=live |archive-url=https://web.archive.org/web/20131102161846/http://www.advantagesix.com/Thea75.html |archive-date=2 November 2013 |access-date=9 February 2012 |work=advantagesix.com}}</ref> || || {{n/a}} || {{n/a}}
|-
| colspan="8" |'''ARM with 32-bit program counter'''
|-
| [[Iyonix PC|Iyonix Ltd Iyonix PC]] || ARMv5TE || 2002 || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}} || 5.01 || 5.30<ref>{{cite web |title=RISC OS Open: Iyonix |url=https://www.riscosopen.org/content/downloads/iyonix |url-status=live |archive-url=https://web.archive.org/web/20150411180000/https://www.riscosopen.org/content/downloads/iyonix |archive-date=11 April 2015 |access-date=25 April 2015 |work=riscosopen.org}}</ref>/5.31
|-
| [[A9home|Advantage Six A9]] (Home/RM/Loc) || ARMv4T || 2005 || {{n/a}} || {{n/a}} || 4.42<ref name="select-faq" /> || || {{n/a}} || {{n/a}}
|-
| [[BeagleBoard]]<ref name="theinquirer snaps leak" /> || rowspan="6" | ARMv7-A || 2008 || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}} || rowspan="4" | 5.15 || rowspan="5" | 5.30<ref>{{cite web |title=RISC OS Open: BeagleBoard |url=https://www.riscosopen.org/content/downloads/beagleboard |url-status=live |archive-url=https://web.archive.org/web/20150411175957/https://www.riscosopen.org/content/downloads/beagleboard |archive-date=11 April 2015 |access-date=25 April 2015 |work=riscosopen.org}}</ref>/5.31
|-
| [[IGEPv2]]<ref>{{cite web |date=24 January 2010 |title=RISC OS on IGEPv2 |url=https://www.riscosopen.org/forum/forums/5/topics/303 |access-date=19 September 2023}}</ref> || 2009 || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}}
|-
| [[DevKit8000]] || ? || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}}
|-
| Always Innovating [[Touch Book]] || 2009 || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}}
|-
| OpenPandora's [[Pandora (console)|Pandora]] || 2010 || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}} || 5.17<ref name="Pandora port">{{cite web |title=RISC OS Open: Forum: Let's get started with a Pandora port |url=https://www.riscosopen.org/forum/forums/5/topics/166?page=14 |url-status=live |archive-url=https://web.archive.org/web/20140919225512/https://www.riscosopen.org/forum/forums/5/topics/166?page=14 |archive-date=19 September 2014 |access-date=10 July 2012 |work=riscosopen.org}}</ref> 
|-
| [[PandaBoard]]<ref name="iconbar old news for you">{{cite web |last=Lee |first=Jeffrey |date=2 August 2011 |title=Have I Got Old News For You |url=http://www.iconbar.com/articles/Have_I_Got_Old_News_For_You/index1268.html |url-status=live |archive-url=https://web.archive.org/web/20120612074011/http://www.iconbar.com/articles/Have_I_Got_Old_News_For_You/index1268.html |archive-date=12 June 2012 |access-date=28 September 2011 |work=[[The Icon Bar]] |quote=[...] Willi Theiss has recently announced that he's been working on a port of RISC OS to the PandaBoard [...]}}</ref> || 2011 || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}} || 5.17 || 5.30<ref name="ROOL news 2015-04-25" />/5.31
|-
| [[Raspberry Pi]] (1 - 4 and compatible)<ref name="osnews risc os" /><ref>{{Cite web |title=raspberrypi.org |url=http://www.raspberrypi.org/?page_id=43&mingleforumaction=viewtopic&t=919.0 |url-status=dead |archive-url=https://web.archive.org/web/20120229180108/http://www.raspberrypi.org/?page_id=43 |archive-date=29 February 2012 |access-date=1 November 2011}}</ref><ref>{{cite web |date=15 July 2014 |title=Raspberry Pi B+ |url=https://www.riscosopen.org/news/articles/2014/07/15/raspberry-pi-model-b |url-status=live |archive-url=https://web.archive.org/web/20140725122155/https://www.riscosopen.org/news/articles/2014/07/15/raspberry-pi-model-b |archive-date=25 July 2014 |access-date=13 August 2014}}</ref><ref>{{cite web |date=29 February 2016 |title=Raspberry Pi 3 |url=https://www.riscosopen.org/forum/forums/1/topics/3943?page=2#posts-50397 |url-status=live |archive-url=https://web.archive.org/web/20160407201218/https://www.riscosopen.org/forum/forums/1/topics/3943?page=2#posts-50397 |archive-date=7 April 2016 |access-date=26 March 2016}}</ref> || ARMv6, v7-A, v8-A || 2012 || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}} || 5.19 || 5.30/5.31
|-
| [[ISEE (company)#IGEPv5|IGEPv5]]<ref name="RISC OS on IGEPv5">{{cite web |date=9 September 2014 |title=RISC OS on IGEPv5 |url=https://www.riscosopen.org/forum/forums/9/topics/2803 |url-status=live |archive-url=https://web.archive.org/web/20150411204755/https://www.riscosopen.org/forum/forums/9/topics/2803 |archive-date=11 April 2015 |access-date=9 September 2014}}</ref> || rowspan="3" | ARMv7-A || 2014 || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}} || 5.23 || 5.30/5.31
|-
| Wandboard Quad<ref name="armx6 formally announced at last">{{cite web |last=Hudd |first=Vince M. |date=1 February 2015 |title=ARMX6 formally announced at last |url=http://www.riscository.com/2015/armx6-formally-announced/ |url-status=live |archive-url=https://web.archive.org/web/20160104182418/http://www.riscository.com/2015/armx6-formally-announced/ |archive-date=4 January 2016 |access-date=1 November 2015 |website=RISCOSitory |publisher=Soft Rock Software |quote=[...] The heart of the machine is a Freescale i.MX 6 series processor [...]}}</ref><ref name="Mx6">{{cite web |date=26 January 2018 |title=i.Mx6 |url=https://www.riscosopen.org/content/downloads/imx6 |url-status=live |archive-url=https://web.archive.org/web/20181109013617/https://www.riscosopen.org/content/downloads/imx6 |archive-date=9 November 2018 |access-date=26 January 2018}}</ref> || rowspan="2" | 2015 || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}} || 5.21 || 5.31
|-
| Titanium<ref name="pedal to the metal">{{cite web |date=23 October 2015 |title=Preview of a whole new RISC OS platform |url=https://www.riscosopen.org/news/articles/2015/10/23/preview-of-a-whole-new-risc-os-platform |url-status=live |archive-url=https://web.archive.org/web/20151124070340/https://www.riscosopen.org/news/articles/2015/10/23/preview-of-a-whole-new-risc-os-platform |archive-date=24 November 2015 |access-date=23 October 2015}}</ref> || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}} || 5.23 || 5.30/5.31
|-
| [[Pinebook]]<ref>{{cite web |date=8 September 2023 |title=Pinebook port |url=https://www.riscosopen.org/wiki/documentation/show/Pinebook%20port |access-date=19 September 2023}}</ref>  || ARMv8-A || 2017 || {{n/a}} || {{n/a}} || {{n/a}} || {{n/a}} || 5.27 || 5.31
|-
|}
RISC OS can also run on a range of computer system emulators that emulate the earlier Acorn machines listed above:
{| class="wikitable"
|+ RISC OS capable hardware emulators
|-
! Emulator !! Machines emulated !! Host platforms supported !! Latest release
|-
| !A310Emu<ref>{{cite web |title=Welcome to my homepage! |url=http://home.tiscali.nl/jandboer/ |url-status=live |archive-url=https://web.archive.org/web/20130619204318/http://home.tiscali.nl/jandboer/ |archive-date=19 June 2013 |access-date=2 September 2013 |publisher=Home.tiscali.nl}}</ref> || rowspan="6" | Archimedes || RISC OS || 0.59
|-
| Archie<ref>{{cite web |date=12 August 2001 |title=Archie – Acorn Archimedes Emulator |url=http://www.geocities.com/chris-o/ |url-status=dead |archive-url=https://web.archive.org/web/20040206063028/http://www.geocities.com/chris-o |archive-date=6 February 2004 |access-date=2 September 2013}}</ref> ||[[DOS]], [[Microsoft Windows|Windows]] || 0.9 – 10 February 2001
|-
| ArchiEmu<ref>{{cite web |title=Tellima |url=http://www.tellima.nl/riscos/ |url-status=live |archive-url=https://web.archive.org/web/20151222081521/http://www.tellima.nl/riscos/ |archive-date=22 December 2015 |access-date=13 December 2015}}</ref> || RISC OS || 0.53.3 – 7 December 2014
|-
| ArcEm<ref>{{cite web |title=ArcEm – The Acorn Archimedes Emulator |url=http://arcem.sourceforge.net/ |url-status=live |archive-url=https://web.archive.org/web/20130809130647/http://arcem.sourceforge.net/ |archive-date=9 August 2013 |access-date=2 September 2013 |publisher=Arcem.sourceforge.net}}</ref> || Windows, [[Linux]], [[macOS]], RISC OS || 1.50.1 – 18 December 2015
|-
| Arculator<ref>{{cite web |title=Arculator – The Acorn Archimedes Emulator |url=http://b-em.bbcmicro.com/arculator/ |url-status=live |archive-url=https://web.archive.org/web/20130621075124/http://b-em.bbcmicro.com/arculator/ |archive-date=21 June 2013 |access-date=11 September 2019 |publisher=B-em.bbcmicro.com}}</ref> || Windows, Linux || 2.2 – 24 June 2023
|-
| [[VirtualAcorn|Virtual A5000]] || rowspan="2" | Windows || 1.4
|-
| Red Squirrel<ref>{{cite web |title=Red Squirrel Acorn Archimedes Emulator |url=http://www.redsquirrel.fsnet.co.uk/redsquirrel.html |url-status=live |archive-url=https://web.archive.org/web/20051227213827/http://www.redsquirrel.fsnet.co.uk/redsquirrel.html |archive-date=27 December 2005 |access-date=2 September 2013 |publisher=Redsquirrel.fsnet.co.uk}}</ref> || Archimedes, Risc PC, A7000 || 0.6 – 28 October 2002
|-
| RPCEmu<ref>{{cite web |title=RPCEmu |url=https://www.marutan.net/rpcemu/ |url-status=live |archive-url=https://web.archive.org/web/20130316043123/http://www.marutan.net/rpcemu/ |archive-date=16 March 2013 |access-date=7 November 2017 |publisher=Marutan.net}}</ref> || Risc PC, A7000, Phoebe || Windows, Linux, macOS, [[OpenBSD]] || 0.9.4 – 30 October 2021
|-
|[[VirtualAcorn|VirtualRPC]]|| Risc PC || Windows, macOS || 5 September 2014<ref>{{cite web |title=VirtualAcorn |url=http://www.virtualacorn.co.uk/news.htm |work=virtualacorn.co.uk}}</ref>
|}

== See also ==
* [[Acorn C/C++]]
* [[ArtWorks]]
* [[Drobe]]
* [[ROX Desktop]], a graphical desktop environment for the X Window System, inspired by the user interface of RISC OS
* [[Sibelius (scorewriter)]], originally an application for RISC OS, rewritten for Windows in 1998
* [[RISC OS character set]]

== Notes ==
<references group="lower-alpha" />
== References ==
{{Reflist|30em|refs=
<ref name="drobe williams 2002">{{cite news|last=Williams|first=Chris|title=Aemulor: Number of apps working on Iyonix 'growing daily'|url=http://www.drobe.co.uk/article.php?id=488|access-date=21 June 2012|newspaper=[[Drobe]]|date=19 November 2002|archive-date=2 February 2014|archive-url=https://web.archive.org/web/20140202124533/http://www.drobe.co.uk/article.php?id=488|url-status=live}}</ref>

<ref name="drobe williams 2003">{{cite news|last=Williams|first=Chris|title=Aemulor sees the light of day|url=http://www.drobe.co.uk/riscos/artifact602.html|access-date=27 June 2012|newspaper=[[Drobe]]|date=25 March 2003|archive-date=2 February 2014|archive-url=https://web.archive.org/web/20140202131856/http://www.drobe.co.uk/riscos/artifact602.html|url-status=live}}</ref>
}}

==External links==
* {{Official website|www.riscosopen.org/content}} RISC OS Open

{{RISC OS|state=expanded}}
{{Acorn computers, clones and compatibles}}
{{Operating system}}

[[Category:RISC OS| ]]
[[Category:Acorn Computers operating systems]]
[[Category:ARM operating systems]]
[[Category:Desktop environments]]
[[Category:Free software operating systems]]<!--because RISC OS 5 finally free, but not historically, nor RISC OS 6-->
[[Category:Software using the Apache license]]
[[Category:Window-based operating systems]]
[[Category:1987 software]]