RISC OS

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

Written in| BBC BASIC, C, C++, assembly language
Working state| Current
Source model| Closed source; open source for some versions since 2018
Initial release| 25 September 1987; 38 years ago (1987-09-25)[1]
|Final release|Latest release}}|

* 5.30[2] / 27 April 2024; 2 years ago (2024-04-27)
* 6.20 / 1 December 2009; 16 years ago (2009-12-01)

|Final preview|Latest preview}}| 5.31
Marketing target| Acorn personal computers
Available in| English
Update method| Flash ROM, OTP ROM, or loadable ROM image
Package manager| PackMan, RiscPkg
Platforms| ARM
Kernel type| Monolithic
Default user interface| GUI
License|

* Apache License 2.0[3] (version 5)
* Proprietary (version 6)

Preceded by| MOS (discontinued)
ARX (discontinued)
Official website| riscosopen.org RISC OS Open
riscos.com RISCOS

RISC OS (/rɪsk.oʊˈɛs/)[4] is an operating system designed to run on ARM computers. Originally designed in 1987 by Acorn Computers of England, it was made for use in its new line of ARM-based 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.[5]

RISC OS is a 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, A7000, and prototype models such as the Acorn NewsPad and Phoebe computer. A version of the OS, named NCOS, was used in Oracle's Network Computer and compatible systems.

After the break-up of Acorn, development of the OS was forked and continued separately by several companies, including RISCOS Ltd, Pace Micro Technology, Castle Technology, and RISC OS Developments.[6] Since then, it has been bundled with several ARM-based desktop computers such as the Iyonix PC[7] and A9home. Most recent stable versions run on the ARMv3/ARMv4 RiscPC, the ARMv5 Iyonix,[8] ARMv7 Cortex-A8 processors[9][10][lower-alpha 1] and Cortex-A9 processors[11][lower-alpha 2] and the low-cost educational Raspberry Pi series of computers, with the exception of the Raspberry Pi 5.[12][13][14]

## Contents

* 1 History
* 2 Features
* 2.1 OS core
* 2.2 File system
* 2.3 File formats
* 2.4 Kernel
* 2.5 Desktop
* 2.6 Font manager
* 2.7 Bundled applications
* 3 Backward compatibility
* 4 Supported hardware
* 5 See also
* 6 Notes
* 7 References
* 8 External links

## History

Main article: Software:History of RISC OS

Original cogwheel logo

The first version of RISC OS was originally released in 1987 as Arthur 1.20. The next version, Arthur 2, became 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.[15]

An Acorn Archimedes A3020 computer running RISC OS

Acorn officially halted work on the OS in January 1999, renaming themselves 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 boxes. In 2000, as part of the acquisition of Acorn Group plc by MSDW Investment, RISC OS was sold to Pace Micro Technology,[16] 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 images, 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 (in contrast to 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 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.[17]

In 2018 RISC OS Developments acquired Castle Technology Ltd including its intellectual property.[6]

In December 2020, the source code of RISC OS 3.71 was leaked to The Pirate Bay.[citation needed]

## Features

### OS core

The OS is single-user and employs cooperative multitasking (CMT).[18] While most current desktop OSes use preemptive multitasking (PMT) and multithreading, RISC OS remains with a CMT system. By 2003, many users had called for the OS to migrate to PMT.[19] The OS memory protection is not comprehensive.[20][21] A third party attempt to add preemptive multitasking was started in 1999, as the Wimp2 project,[22] and similar goal added to the RISC OS Open roadmap in 2015.[23] In addition support for Posix / SysV / BSD pthread (preemptive-threading) was made available through the provision of UnixLib 3.6 in 1992, a C library introduced to permit the porting of the standard GNU / BSD tool chains to RISC OS, by Alun Jones, then of the Higher Education National Software Archive (HENSA). As of 2025 UnixLib is available through the PackMan package manager.

The core of the OS is stored in ROM, giving a fast bootup time and safety from operating system corruption. RISC OS 4 and 5 are stored in 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 modules. 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 calls in other operating systems.

Most of the OS has defined application binary interfaces (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

The file system is volume-orientated: 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 extensions. Colons are used to separate the file system from the rest of the path; the root is represented by a dollar (`$`) sign and directories are separated by a full stop (`.`). Extensions from foreign file systems are shown using a slash (`example.txt` becomes `example/txt`).[24] For example, `ADFS::HardDisc4.$` is the root of the disc named HardDisc4 using the Advanced Disc Filing System (ADFS) file system. RISC OS filetypes can be preserved on other systems by appending the hexadecimal type as '`,xxx`' to filenames.[24][25] When using cross-platform software, filetypes can be invoked on other systems by naming appending '`/[extension]`' to the filename under RISC OS.[26]

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.

### File formats

Main article: List of RISC OS filetypes

The OS uses metadata to distinguish file formats. Some common file formats from other systems are mapped to filetypes by the MimeMap module.[27]

### Kernel

The RISC OS kernel is single-tasking and controls handling of interrupts, DMA services, memory allocation and the video display; the cooperative multi-tasking is provided by the WindowManager module.[18]

### Desktop

A screenshot of RISC OS 4

The WIMP interface is based on a stacking window manager and incorporates three mouse buttons[28] (named Select, Menu and Adjust), context-sensitive menus, window order control (i.e. send to back) and dynamic window focus (a window can have input focus at any position on the stack). The icon bar (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 (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 RISC OS Style Guide encourages a consistent look and feel across applications. This was introduced in RISC OS 3 and specifies application appearance and behaviour. Acorn's own main bundled applications were not updated to comply with the guide until RISCOS Ltd's Select release in 2001.[29]

### Font manager

RISC OS was the first operating system to provide scalable anti-aliased fonts.[30][31][32][33] Anti-aliased fonts were already familiar from Arthur, and their presence in RISC OS was confirmed in an early 1989 preview,[34] featuring in the final RISC OS 2 product, launched in April 1989.[35]

A new version of the font manager employing "new-style outline fonts" was made available after the release of RISC OS,[36] offering full support for the printing of scalable fonts, and was provided with Acorn Desktop Publisher.[37] It was also made available separately and bundled with other applications.[38] This outline font manager provides support for the rendering of font outlines to bitmaps for screen and printer use, employing anti-aliasing for on-screen fonts, utilising sub-pixel anti-aliasing and caching for small font sizes.[39] 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.[40]

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 system font from previous versions.[41][42] 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."[43]

Support for the characters of RISC OS (and some other historic computers) was added to Unicode 13.0 (in 2020).[44]

### Bundled applications

Main article: Software:List of RISC OS bundled applications

RISC OS is available in several distributions, all of which include a small standard set of desktop applications, 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. Successive OS upgrades have raised more serious issues of backward compatibility for desktop applications and games.[45] 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). Patching of applications for the StrongARM was facilitated and Acorn's UnsqueezeAIF software unsqueezed images according to their AIF header.[46] The incompatibilities prompted release by The ARM Club of its Game On![47][48] and StrongGuard software.[47][49][50] 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)[51] to stop "trashing the desktop".[52]

The Iyonix PC (RISC OS 5) and A9home (custom RISC OS 4) saw further software incompatibility because of the deprecated 26-bit addressing modes. Most applications under active development have since been rewritten.[53][54][55] Static code analysis to detect 26-bit-only sequences can be undertaken using ARMalyser.[56] Its output can be helpful in making 32-bit versions of older applications for which the source code is unavailable.[57][56][58] Some older 26-bit software can be run without modification using the Aemulor emulator.[55][59][60]

Additional incompatibilities were introduced with newer ARM cores, such as ARMv7 in the BeagleBoard and ARMv8 in the Raspberry Pi 3. This includes changes to unaligned memory access in ARMv6/v7 and removal of the SWP instructions in ARMv8.[61]

## Supported hardware

RISC OS has also been used by both Acorn and Pace Micro Technology in various TV connected set-top boxes, sometimes referred to instead as NCOS. A special cut down RISC OS Pico (for 16MiB cards and larger) styled to start up like a BBC Micro was released for BASIC's 50th anniversary.[62] 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[63] and a command-line interface only version (RISC OS Pico, at 3.8 MB).[64]

Versions of RISC OS run or have run on the following hardware: (RISC OS Open Limited adopted[65] the '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.)

RISC OS compatible hardware  Machine | ARM architecture | Introduced | Acorn version | RISCOS Ltd version | Castle Technology, RISC OS Open version

|
|
|
|
|

First | Last | First | Last | First | Latest
ARM with 26-bit program counter
Acorn Archimedes | ARMv2 | 1987–1992 | 0.20 | 3.1x | N/A | N/A | N/A | N/A
ARM with 26- & 32-bit program counter
Acorn Risc PC | ARMv3 / v4 | 1994[66] | 3.50[66] | 3.71 | 4.00 | 6.20[67] | 5.15 | 5.30[68]/5.31
Acorn A7000 and A7000+ | ARMv3 | 1995[69] - 1997[70] | 3.60[69][70]
Acorn Phoebe (cancelled) | ARMv4 | 1998 | 3.80 (Ursula) | N/A | N/A | N/A | N/A | N/A
MicroDigital Medi[71] | ARMv3 | 1998[72] | 3.71[72] | N/A | 4.02 | 6.20 | N/A | N/A
MicroDigital Mico | 1999[73] | N/A | N/A | 4.03[73] | 4.39[67] | N/A | N/A
RiscStation R7500 | 1999[74] | N/A | N/A | 4.03[74] | 4.39[67] | N/A | N/A
Castle Kinetic RiscPC | ARMv4 | 2000[75] | N/A | N/A | 4.03 | 6.20 | 5.19[76] | 5.30[68]/5.31
MicroDigital Omega | 2003[77] | N/A | N/A | 4.03[78] | 4.39[67] | N/A | N/A
Advantage Six A75 | ARMv3 | 2004[79] | N/A | N/A | 4.39[80] |  | N/A | N/A
ARM with 32-bit program counter
Iyonix Ltd Iyonix PC | ARMv5TE | 2002 | N/A | N/A | N/A | N/A | 5.01 | 5.30[81]/5.31
Advantage Six A9 (Home/RM/Loc) | ARMv4T | 2005 | N/A | N/A | 4.42[67] |  | N/A | N/A
BeagleBoard[9] | ARMv7-A | 2008 | N/A | N/A | N/A | N/A | 5.15 | 5.30[82]/5.31
IGEPv2[83] | 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 | 2010 | N/A | N/A | N/A | N/A | 5.17[84]
PandaBoard[85] | 2011 | N/A | N/A | N/A | N/A | 5.17 | 5.30[11]/5.31
Raspberry Pi (1 - 4 and compatible)[13][86][87][88] | ARMv6, v7-A, v8-A | 2012 | N/A | N/A | N/A | N/A | 5.19 | 5.30/5.31
IGEPv5[89] | ARMv7-A | 2014 | N/A | N/A | N/A | N/A | 5.23 | 5.30/5.31
Wandboard Quad[90][91] | 2015 | N/A | N/A | N/A | N/A | 5.21 | 5.31
Titanium[92] | N/A | N/A | N/A | N/A | 5.23 | 5.30/5.31
Pinebook[93] | 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:

RISC OS capable hardware emulators  Emulator | Machines emulated | Host platforms supported | Latest release

|
|
|

!A310Emu[94] | Archimedes | RISC OS | 0.59
Archie[95] | DOS, Windows | 0.9 – 10 February 2001
ArchiEmu[96] | RISC OS | 0.53.3 – 7 December 2014
ArcEm[97] | Windows, Linux, macOS, RISC OS | 1.50.1 – 18 December 2015
Arculator[98] | Windows, Linux | 2.2 – 24 June 2023
Virtual A5000 | Windows | 1.4
Red Squirrel[99] | Archimedes, Risc PC, A7000 | 0.6 – 28 October 2002
RPCEmu[100] | Risc PC, A7000, Phoebe | Windows, Linux, macOS, OpenBSD | 0.9.5 – 23 October 2024
VirtualRPC | Risc PC | Windows, macOS | 5 September 2014[101]

## 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

1. ↑ (such as that used in the BeagleBoard and Touch Book)
2. ↑ (such as that used in the PandaBoard)

## References

1. ↑ copyright notice Arthur 1.20 (25 September 1987)
2. ↑ Revill, Steve (27 April 2024). "RISC OS 5.30 now available". RISC OS Open. https://www.riscosopen.org/news/articles/2024/04/27/risc-os-5-30-now-available.
3. ↑ RISC OS is open for business! , RISC OS Open Ltd, accessed 23 October 2018
4. ↑ "RISC OS". ISV Department news from Acorn (Acorn Computers Limited) (14): pp. 2. May 1989. http://chrisacorns.computinghistory.org.uk/docs/Acorn/DN/Acorn_DevNL14.pdf. "It is RISC OS (pronounced risk oh ess, not risk oss)"
5. ↑ Proven, Liam (21 June 2022). "RISC OS: 35-year-old original Arm operating system is alive and well". The Register. https://www.theregister.com/2022/06/21/risc_os_35/.
6. ↑ 6.0 6.1 "Home". https://www.riscosdev.com/.
7. ↑ "Acorn announces distribution deal with Castle Technology for RISC based products" (Press release). Acorn Computers Ltd. 12 October 1998. Archived from the original on 6 May 1999. Retrieved 6 January 2011. "(October 12th 1998), Cambridge, UK-Acorn announced today that it has completed negotiations with Castle Technology for them to distribute Acorn products."
8. ↑ "RISC OS 5 features". Iyonix Ltd. http://www.iyonix.com/iyonix/features/osfeatures.shtml. "All IYONIX pcs ship with RISC OS 5 in flash ROM."
9. ↑ 9.0 9.1 Farrell, Nick (27 April 2009). "Snaps leak of RISC OS5 on BeagleBoard". The Inquirer. http://www.theinquirer.net/inquirer/news/1051924/snaps-leak-risc-os5-beagleboard. "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."
10. ↑ "Cortex-A8 port status". RISC OS Open. https://www.riscosopen.org/wiki/documentation/pages/Cortex-A8+port+status/versions/1. "[The port includes] a modified version of the RISC OS kernel containing support for (all) Cortex-A8 CPU cores."
11. ↑ 11.0 11.1 Revill, Steve (25 April 2015). "RISC OS 5.22 stable is now available". RISC OS Open. https://www.riscosopen.org/news/articles/2015/04/25/risc-os-5-22-stable-is-now-available.
12. ↑ Lee, Jeffrey. "Newsround". The Icon Bar. http://www.iconbar.com/articles/Newsround/index1271.html.
13. ↑ 13.0 13.1 Holwerda, Thom (31 October 2011). "Raspberry Pi To Embrace RISC OS". OSNews. http://www.osnews.com/story/25276/Raspberry_Pi_To_Embrace_RISC_OS.
14. ↑ Dewhurst, Christopher (December 2011). "The London show 2011". Archive 23 (3): p. 3.
15. ↑ "ART – Acorn RISC OS". acorn.chriswhy.co.uk. http://acorn.chriswhy.co.uk/docs/Acorn/ART/ART_DS013_AcornRISCOS.pdf.
16. ↑ Cullen, Drew (24 April 1999). "ARM denies role in Acorn dismemberment". The Register. https://www.theregister.com/1999/04/29/arm_denies_role_in_acorn/.
17. ↑ Speed, Richard. "Roughly 30 years after its birth at UK's Acorn Computers, RISC OS 5 is going open source". The Register. https://www.theregister.com/2018/10/23/risc_os_open_source/.
18. ↑ 18.0 18.1 Palmer, Stewart (December 1996). "A RISC OS for All Seasons". Byte 21 (12): 49. ISSN 0360-5280. OCLC 208951251. https://archive.org/details/eu_BYTE-1996-12_OCR/page/n84/mode/1up.
19. ↑ Williams, Chris (26 July 2003). "Imagining RISC OS and PMT". Drobe. http://www.drobe.co.uk/article.php?id=764.
20. ↑ Michael Reed Tech Book 1 – Published articles Oct 2006 – June 2008
21. ↑ "RISC OS Memory Protection". http://www.drobe.co.uk/riscos/artifact1327.html.
22. ↑ "ned Productions - RISC-OS programs - Wimp2". https://www.nedprod.com/programs/RISC-OS/Wimp2/.
23. ↑ "RISC OS Open: RISC OS Roadmap in Library" (in en). https://www.riscosopen.org/wiki/documentation/show/RISC OS Roadmap.
24. ↑ 24.0 24.1 Naulls, Peter (2 January 2004). "RISC OS filename translation". Drobe. http://www.drobe.co.uk/article.php?id=921.
25. ↑ "Emulating RISC OS, Page 3/3". http://www.osnews.com/story/6170/Emulating_RISC_OS_under_Windows/page3/.
26. ↑ Fitton, Gerald (August 1994), "Fireworkz for Windows", Archive (Glastonbury: Abbey Press) 7 (11): 21, OCLC 222434223, http://downloads.abacusline.me.uk/pdf/Arc/2007/GC0701.pdf, retrieved 25 April 2012
27. ↑ "Iyonix: MIMEMap". iyonix.com. http://www.iyonix.com/32bit/MIMEMap.shtml.
28. ↑ Ryan, Dan (13 April 2011). History of Computer Graphics: DLR Associates Series. AuthorHouse. p. 358. ISBN 978-1-4567-5115-9. https://books.google.com/books?id=136myWlKpwEC&pg=PA358. Retrieved 13 June 2013.
29. ↑ Phil, Mellor (23 March 2007). "An arbitrary number of possibly influential RISC OS things". The Icon Bar. http://www.iconbar.com/articles/Influential/index1152.html. "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."
30. ↑ Round, Mark (26 February 2004). "Emulating RISC OS under Windows". OSnews. http://www.osnews.com/story/6170/Emulating_RISC_OS_under_Windows/page1/. "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."
31. ↑ Ghiraddje (22 December 2009). "The RISC OS GUI". Telcontar.net. http://telcontar.net/Misc/GUI/RISCOS/. "Only with Mac OS X did any mainstream graphical interface provide the smoothly rendered, fractionally spaced type that Acorn accomplished in 1992 or earlier."
32. ↑ Reimer, Jeremy (May 2005). "A History of the GUI". ArsTechnica. https://arstechnica.com/old/content/2005/05/gui.ars/6. "[...] 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!"
33. ↑ Holwerda, Thom (23 June 2005). "Screen Fonts: Shape Accuracy or On-Screen Readability?". OSNews. http://www.osnews.com/story/21713/Screen_Fonts_Shape_Accuracy_or_On-Screen_Readability_. "[...] it was RISC OS that had the first system-wide, intricate [...] font rendering in operating systems."
34. ↑ Pountain, Dick (January 1989). "Screentest: Archie RISC OS". Personal Computer World: p. 154. http://chrisacorns.computinghistory.org.uk/docs/Mags/PCW/PCW_Jan89_RISCOS.pdf. "[ArcDraw] can also add text in multiple sizes and fonts to a drawing (including anti-aliased fonts)"
35. ↑ "RISC OS is ready for April launch". Acorn User: pp. 9. February 1989. https://archive.org/details/AcornUser079-Feb89/page/n10/mode/1up.
36. ↑ "New fonts for DTP". Acorn User: pp. 7. April 1989. https://archive.org/details/AcornUser081-Apr89/page/n8/mode/1up.
37. ↑ Bell, Graham (October 1989). "Hold the Font Page". Acorn User: pp. 134–135. https://archive.org/details/AcornUser087-Oct89/page/n135/mode/2up.
38. ↑ "Acorn Customer Hotline". Acorn User: pp. 19. April 1990. https://archive.org/details/AcornUser093-Apr90/page/n20/mode/1up.
39. ↑ Raine, Neil; Seal, David; Stoye, William; Wilson, Roger (November 1989). "The Acorn Outline Font Manager". Fifth Computer Graphics Workshop. Monterey, California: USENIX Association. pp. 25–36. https://archive.org/details/1989-proceedings-5th-comp-graphics-workshop/page/25/mode/1up.
40. ↑ Bell, Graham (November 1989). "My Type". Acorn User: pp. 68–69. https://archive.org/details/AcornUser088-Nov89/page/n69/mode/2up.
41. ↑ "Acorn signs pre-press deal". Acorn User (Addison-Wesley): 10. July 1993. https://archive.org/details/AcornUser132-Jul93/page/n11/mode/2up.
42. ↑ Murphy, Dean (29 March 1994). Acorn Computers Support Group Application Notice 253 – New features of RISC OS version 3.5 (PDF) (Technical report). Acorn Computers Limited. Retrieved 2 March 2022.
43. ↑ "Unicode in RISC OS". riscos.info. http://www.riscos.info/index.php/Unicode_in_RISC_OS.
44. ↑ "The Unicode® Standard Version 13.0 – Core Specification". https://www.unicode.org/versions/Unicode13.0.0/ch22.pdf.
45. ↑ "ARM architecture versions cheat sheet". http://www.starfighter.acornarcade.com/mysite/articles/armv.html.
46. ↑ "Application Note 295". Engineering Support Application Note. Acorn Computers. 4 October 1996. http://acorn.riscos.com/riscos3/37/37DiscImage/Manuals/AppNote.
47. ↑ 47.0 47.1 Foggy (11 July 2001). "Games FAQ". Acorn Arcade. http://acornarcade.com/articles/Games_FAQ/index1004.html.
48. ↑ Ruck, David J.. "Game On!". David J. Ruck. http://www.armclub.org.uk/products/gameon/.
49. ↑ Ruck, David J.. "StrongGuard". David J. Ruck. http://www.armclub.org.uk/products/strongguard/.
50. ↑ McKillop, Keith (22 November 2000). "RISC OS 2000: Show Report". Acorn Arcade. http://acornarcade.com/RISC_OS_2000_Show_Report/news971.html.
51. ↑ "RISCOS Ltd News". RISCOS Ltd. May 2006. http://www.riscos.com/news/news_items/NewsMay2006.pdf.
52. ↑ Williams, Chris (17 April 2006). "ROL release C99 SCL to A9home users". Drobe. http://www.drobe.co.uk/article.php?id=1580.
53. ↑ Thompson, Matt. "Iyonix Issues". RISC World 7 (2). http://www.apdl.co.uk/riscworld/volume7/issue2/iyonix/.
54. ↑ Thompson, Matt. "Iyonix Issues". RISC World 8 (2). http://www.apdl.co.uk/riscworld/volume8/issue2/iyonix/.
55. ↑ 55.0 55.1 "A Guide to RISC OS Versions". WROCC website. Wakefield RISC OS Computer Club. http://www.wrocc.org.uk/riscos/versions.shtml.
56. ↑ 56.0 56.1 Brett, Paul. "PD World". RISC World 7 (1). http://www.apdl.co.uk/riscworld/volume7/issue1/pd/.
57. ↑ Brett, Paul. "PD World". RISC World 3 (1). http://www.apdl.co.uk/riscworld/volume3/issue1/pd/.
58. ↑ Ruck, David J.. "Free Software". David J. Ruck. http://www.armclub.org.uk/free/.
59. ↑ Williams, Chris (19 November 2002). "Aemulor: Number of apps working on Iyonix 'growing daily'". Drobe. http://www.drobe.co.uk/article.php?id=488.
60. ↑ Williams, Chris (25 March 2003). "Aemulor sees the light of day". Drobe. http://www.drobe.co.uk/riscos/artifact602.html.
61. ↑ "ARMv7 compatibility primer in Documentation". https://www.riscosopen.org/wiki/documentation/show/ARMv7 compatibility primer#TOC3.11.
62. ↑ "Happy birthday, BASIC". 5 January 2014. https://www.riscosopen.org/news/articles/2014/05/01/happy-birthday-basic.
63. ↑ "Downloads". Raspberry Pi. http://www.raspberrypi.org/downloads.
64. ↑ "RISC OS Open: Raspberry Pi". riscosopen.org. https://www.riscosopen.org/content/downloads/raspberry-pi.
65. ↑ "Stable release criteria". 12 January 2017. https://www.riscosopen.org/content/documents/stable-releases.
66. ↑ 66.0 66.1 "Chris's Acorns: Risc PC Computers". http://chrisacorns.computinghistory.org.uk/Computers/RiscPCComputers.html.
67. ↑ 67.0 67.1 67.2 67.3 67.4 "RISC OS Six Frequently Asked Questions". http://select.riscos.com/RISCOS6/faq.html.
68. ↑ 68.0 68.1 "RISC OS Open: RiscPC". https://www.riscosopen.org/content/downloads/riscpc.
69. ↑ 69.0 69.1 "Chris's Acorns: Acorn A7000". computinghistory.org.uk. http://chrisacorns.computinghistory.org.uk/Computers/A7000.html.
70. ↑ 70.0 70.1 "Chris's Acorns: Acorn A7000+". computinghistory.org.uk. http://chrisacorns.computinghistory.org.uk/Computers/A7000+.html.
71. ↑ repackaged A7000+
72. ↑ 72.0 72.1 "Chris's Acorns: MicroDigital". computinghistory.org.uk. http://chrisacorns.computinghistory.org.uk/AfterAcorn/Microdigital.html#Medi.
73. ↑ 73.0 73.1 "Chris's Acorns: MicroDigital". computinghistory.org.uk. http://chrisacorns.computinghistory.org.uk/AfterAcorn/Microdigital.html#Mico.
74. ↑ 74.0 74.1 "Chris's Acorns: RISC OS After Acorn". computinghistory.org.uk. http://chrisacorns.computinghistory.org.uk/AfterAcorn.html#RiscStation.
75. ↑ "The Icon Bar: Castle reveal Kinetic to the press". iconbar.com. http://www.iconbar.com/forums/viewthread.php?newsid=918.
76. ↑ "Bugs and sources". RISC OS Open. 28 March 2013. https://www.riscosopen.org/viewer/revisions/logs?ident=1364507316-018164.html.
77. ↑ "Omega production saga continues – Drobe.co.uk archives". drobe.co.uk. http://www.drobe.co.uk/article.php?id=973.
78. ↑ "Chris's Acorns: MicroDigital". computinghistory.org.uk. http://chrisacorns.computinghistory.org.uk/AfterAcorn/Microdigital.html#Omega.
79. ↑ "A75 is ARM7500FE ruggable – Drobe.co.uk archives". drobe.co.uk. http://www.drobe.co.uk/article.php?id=1047.
80. ↑ "Advantage6: Thea75". advantagesix.com. http://www.advantagesix.com/Thea75.html.
81. ↑ "RISC OS Open: Iyonix". riscosopen.org. https://www.riscosopen.org/content/downloads/iyonix.
82. ↑ "RISC OS Open: BeagleBoard". riscosopen.org. https://www.riscosopen.org/content/downloads/beagleboard.
83. ↑ "RISC OS on IGEPv2". 24 January 2010. https://www.riscosopen.org/forum/forums/5/topics/303.
84. ↑ "RISC OS Open: Forum: Let's get started with a Pandora port". riscosopen.org. https://www.riscosopen.org/forum/forums/5/topics/166?page=14.
85. ↑ Lee, Jeffrey (2 August 2011). "Have I Got Old News For You". The Icon Bar. http://www.iconbar.com/articles/Have_I_Got_Old_News_For_You/index1268.html. "[...] Willi Theiss has recently announced that he's been working on a port of RISC OS to the PandaBoard [...]"
86. ↑ "raspberrypi.org". http://www.raspberrypi.org/?page_id=43&mingleforumaction=viewtopic&t=919.0.
87. ↑ "Raspberry Pi B+". 15 July 2014. https://www.riscosopen.org/news/articles/2014/07/15/raspberry-pi-model-b.
88. ↑ "Raspberry Pi 3". 29 February 2016. https://www.riscosopen.org/forum/forums/1/topics/3943?page=2#posts-50397.
89. ↑ "RISC OS on IGEPv5". 9 September 2014. https://www.riscosopen.org/forum/forums/9/topics/2803.
90. ↑ Hudd, Vince M. (1 February 2015). "ARMX6 formally announced at last". Soft Rock Software. http://www.riscository.com/2015/armx6-formally-announced/. "[...] The heart of the machine is a Freescale i.MX 6 series processor [...]"
91. ↑ "i.Mx6". 26 January 2018. https://www.riscosopen.org/content/downloads/imx6.
92. ↑ "Preview of a whole new RISC OS platform". 23 October 2015. https://www.riscosopen.org/news/articles/2015/10/23/preview-of-a-whole-new-risc-os-platform.
93. ↑ "Pinebook port". 8 September 2023. https://www.riscosopen.org/wiki/documentation/show/Pinebook port.
94. ↑ "Welcome to my homepage!". Home.tiscali.nl. http://home.tiscali.nl/jandboer/.
95. ↑ "Archie – Acorn Archimedes Emulator". 12 August 2001. http://www.geocities.com/chris-o/.
96. ↑ "Tellima". http://www.tellima.nl/riscos/.
97. ↑ "ArcEm – The Acorn Archimedes Emulator". Arcem.sourceforge.net. https://arcem.sourceforge.net/.
98. ↑ "Arculator – The Acorn Archimedes Emulator". B-em.bbcmicro.com. http://b-em.bbcmicro.com/arculator/.
99. ↑ "Red Squirrel Acorn Archimedes Emulator". Redsquirrel.fsnet.co.uk. http://www.redsquirrel.fsnet.co.uk/redsquirrel.html.
100. ↑ "RPCEmu". Marutan.net. https://www.marutan.net/rpcemu/.
101. ↑ "VirtualAcorn". virtualacorn.co.uk. http://www.virtualacorn.co.uk/news.htm.

## External links

* Official website RISC OS Open

* v
* t
* e

RISC OS

Category: RISC OS software

Main companiesa|

* Castle Technology
* RISC OS Open

Hardware|

* Archimedes series
* RiscPC series
* Iyonix
* A9home

Emulation|

* Aemulor
* VirtualAcorn

Key softwareb|

* ArtWorks
* Impression
* NetSurf

OS components|

* ADFS
* AIF file
* BBC BASIC
* Bundled applications
* Drag and drop
* Icon bar
* OLE
* Ram disk

OS utilities|

* MakeModes

Books|

* ARM system-on-chip architecture

Related and historical|

* Acorn Computers
* ARM Holdings
* Element 14
* Galileo
* History of RISC OS
* Phoebe
* RISCOS Ltd
* The Electronic Font Foundry
* NCOS

* a Current companies only
* b Addition of major functionality

* v
* t
* e

Acorn Computers, derivatives, clones and compatibles

Operating systems|

* Acorn MOS
* Panos
* ARX
* RISC iX
* RISC OS
* Galileo
* NCOS

Acorn brand|

| 8-bit microcomputers|

* Microcomputer
* Systems 2 to 5
* Atom
* BBC Micro (Proton)
* Electron
* Communicator
* Business Computer
* BBC Master

|

32-bit PCs|

* Archimedes range
* A4
* RiscPC
* A7000
* Set-Top Box
* Network Computer
* Phoebe

Derivatives, clones,
compatibles|

| 8-bit microcomputers|

* Prodest PC128S

|

32-bit PCs|

* A9home
* ARMini (BeagleBoard-xM)
* BIK (BeagleBoard-xM in Kiste)
* Omega
* Mico
* Medi
* RiscStation R7500
* A75
* Iyonix

32-bit dev boards|

* BeagleBoard
* DevKit8000
* IGEPv2
* Pandora
* PandaBoard
* Raspberry Pi
* Touch Book

* v
* t
* e

Operating systems

General|

* Advocacy
* Comparison
* Forensic engineering
* History
* Hobbyist development
* List
* Timeline
* Usage share

Kernel|

| Architectures|

* Exokernel
* Hybrid
* Microkernel
* Monolithic
* vkernel
* Rump kernel
* Unikernel

|

Components|

* Device driver
* Loadable kernel module
* Microkernel
* User space

Process management|

| Concepts|

* Context switch
* Interrupt
* IPC
* Process
* Process control block
* Real-time
* Thread
* Time-sharing

|

Scheduling
algorithms|

* Computer multitasking
* Fixed-priority preemptive
* Multilevel feedback queue
* Preemptive
* Round-robin
* Shortest job next

Memory management and
resource protection|

* Bus error
* General protection fault
* Memory protection
* Paging
* Protection ring
* Segmentation fault
* Virtual memory

Storage access and
file systems|

* Boot loader
* Defragmentation
* Device file
* File attribute
* Inode
* Journal
* Partition
* Virtual file system
* Virtual tape library

List|

* Acorn
* Arthur
* ARX
* MOS
* RISC iX
* RISC OS
* Amiga Inc.
* AmigaOS
* AmigaOS 1.0-3.9 (Motorola 68000)
* AmigaOS 4 (PowerPC)
* Amiga Unix, a.k.a. Amix
* Amstrad
* AMSDOS
* Contiki
* SymbOS
* Android
* Apple Inc.
* Apple II family
* Apple III
* Apple DOS
* Apple Lisa
* Apple SOS
* Apple Pascal
* ProDOS
* GS/OS
* GNO/ME
* Contiki
* Apple Macintosh
* Classic Mac OS
* A/UX
* Copland
* MkLinux
* Pink
* Rhapsody
* macOS (formerly Mac OS X and OS X)
* macOS Server (formerly Mac OS X Server and OS X Server)
* Apple Network Server
* Apple MessagePad
* Newton OS
* iPhone and iPod Touch
* iOS (formerly iPhone OS)
* iPad
* iPadOS
* Apple Watch
* watchOS
* Apple TV
* tvOS
* Darwin
* iPod
* iPod software (unnamed embedded OS)
* A/ROSE
* Apollo Computer
* Domain/OS
* Atari
* Atari DOS
* Atari TOS
* Atari MultiTOS
* BAE Systems XTS-400
* Be Inc.
* BeOS
* BeIA
* BeOS r5.1d0
* Bell Labs Non-Unix
* BESYS
* Plan 9 from Bell Labs
* Inferno)
* Burroughs Corporation
* Burroughs MCP
* BSD
* Control Data Corporation
* Chippewa Operating System
* Kronos
* NOS (Network Operating System)
* SCOPE)
* Convergent Technologies Operating System
* Cosmos
* Cromemco
* Cromemco DOS
* Cromix
* Data General
* AOS (for 16-bit)
* DG/UX
* RDOS (Real-time DOS)
* Datapoint (CTOS for Z-80)
* DDC-I Inc.
* HeartOS
* Digital Research, Inc.
* CP/M
* CP/M Plus
* CP/M-68K
* CP/M-8000
* CP/M-86
* CP/M-86 Plus
* Concurrent CP/M
* Concurrent CP/M-86
* Concurrent CP/M 8-16
* Concurrent CP/M-68K
* Concurrent DOS
* Concurrent PC DOS
* Concurrent DOS 8-16
* Concurrent DOS 286
* Concurrent DOS XM
* Concurrent DOS 386
* Concurrent DOS 386/MGE
* Concurrent DOS 68K
* DR-DOS
* FlexOS
* FlexOS 186
* FlexOS 286
* FlexOS 68K
* Multiuser DOS
* Datapac Multiuser DOS
* Datapac System Manager, a derivative of Datapac Multiuser DOS
* IMS Multiuser DOS
* MP/M
* MP/M II
* MP/M-86
* MP/M 8-16
* PalmDOS 1.0
* Personal CP/M
* Digital Equipment Corporation
* Batch-11/DOS-11
* OS/8
* RSTS/E
* RSX-11
* RT-11
* TOPS-10
* TOPS-20
* TENEX
* Digital UNIX
* Ultrix
* VMS
* WAITS
* DOS
* ENEA AB OSE
* Fujitsu Towns OS
* General Electric, Honeywell, Bull
* Real-Time Multiprogramming Operating System
* GCOS
* Multics
* Genode
* GNU
* Google
* Android
* Chromium OS
* Chrome OS
* Goobuntu
* Fuchsia)
* Green Hills Software
* INTEGRITY
* INTEGRITY-178B
* µ-velOSity
* Haiku
* Harmony
* Heathkit, Zenith Data Systems
* HDOS
* HT-11
* Hewlett-Packare
* HP-UX
* Multi-Programming Executive
* Honeywell CP-6
* Huawei Harmony OS
* Intel Corporation
* ISIS
* IBM
* Pre-360
* BESYS
* CTSS
* GM OS & GM-NAA I/O
* IBSYS
* SHARE Operating System
* University of Michigan Executive System (UMES)
* OS/360 and successors
* OS/360 and successors
* MVS
* OS/390
* Phoenix/MVS
* z/OS)
* DOS
* DOS/360 and successors on IBM S/360, S/370, and successor mainframes
* BOS/360
* TOS/360
* DOS/VS
* DOS/VSE
* VSE/SP
* VSE/ESA
* z/VSE)
* VM/CMS
* CP/CMS
* CP-40
* CP-67
* VM/370
* VM/XA
* VM/ESA Virtual Machine
* z/VM)
* TPF line
* Airline Control Program ACP
* Transaction Processing Facility)
* Unix-like
* AIX
* UTS (Mainframe UNIX)
* Linux on z Systems
* Others on IBM S/360, S/370, and successor mainframes
* TSS/360
* MUSIC/SP
* ORVYL and WYLBUR
* IBM PC
* PC DOS
* OS/2
* OS/2 Warp
* eComStation)
* Other hardware
* IBM Series 1
* EDX
* RPS
* CPS
* IBM 1130 DM2
* IBM 1800 MPX & TSX
* IBM 8100
* DPCX
* DPPX)
* System 3 DMS
* IBM System 34, 36, 38
* OS/400
* illumos
* IncludeOS
* iOS
* audioOS
* iPadOS
* tvOS
* Linux
* MINIX
* MorphOS
* MUSIC/SP
* Nemesis
* NeXTSTEP
* NOS
* ORVYL
* OS/2
* OS-9
* OSv
* Pick
* QNX
* ReactOS
* RISC OS
* Solaris
* Tandem
* NonStop
* TPF
* TRIPOS
* Unix
* Visi On
* VS/9
* webOS
* Windows
* Xerox 500 series (530 RTB, 560)
* Xinu
* z/OS

Miscellaneous concepts|

* API
* Computer network
* HAL
* Live CD
* Live USB
* OS shell
* CLI
* GUI
* NUI
* TUI
* VUI
* ZUI
* PXE

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