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A screenshot of RISC OS 4
|Company / developer||Castle Technology & RISC OS Open (5.xx), RISCOS Ltd (6.xx)|
|Latest stable release||5.18 or 6.20 / 16 January 2012 or 1 December 2009|
|Latest unstable release||5.21 / 1 June 2013|
|Available programming languages(s)||BBC BASIC, C, C++, assembly language|
|Update method||Flash ROM or OTP ROM|
|License||'Shared Source' (5.xx), Proprietary (6.xx)|
|Official website||RISC OS Open Ltd, RISCOS Ltd|
RISC OS // is a computer operating system originally designed by Acorn Computers Ltd in Cambridge, England in 1987. RISC OS was specifically designed to run on the ARM chipset, which Acorn had designed concurrently, for use in its new line of Archimedes personal computers. It takes its name from the RISC (reduced instruction set computing) architecture supported.
From 1988 to 1998, RISC OS was bundled with every ARM-based Acorn computer model. These included the Acorn Archimedes range, Acorn's R line of computers (with RISC iX as a dual boot option), RiscPC, A7000 and also prototype models such as the Acorn NewsPad and Phoebe computer. A version of the OS (called NCOS) was also used in Oracle's Network Computer and compatible systems.
After the break-up of Acorn in 1998, development of the OS was forked and separately continued by several companies, including RISCOS Ltd, Pace Micro Technology and Castle Technology. Since then, it has been bundled with a number of ARM-based desktop computers such as the Iyonix and A9home. As of 2012[update], the OS remains forked and is independently developed by RISCOS Ltd and the RISC OS Open community.
Most recent stable versions run on the ARMv3/ARMv4 RiscPC, the ARMv5 Iyonix and ARMv7 Cortex-A8 processors (such as that used in the BeagleBoard and Touch Book). In 2011, a port for the Cortex-A9 PandaBoard was announced and a development version for the Raspberry Pi was seen in public which has been followed up with a freely downloadable release candidate; this version has been made available free of charge to Raspberry Pi users.
RISC OS was originally released in 1987 as Arthur 1.20. The next version, Arthur 2, became RISC OS 2 and was completed and made available in April 1989. RISC OS 3.00 was released with the very earliest version of the A5000 in 1991 and contained a series of new features. By 1996 RISC OS had been shipped on over 500,000 systems.
Acorn officially halted work on the OS in January 1999, renaming themselves Element 14. In March 1999 a new company called RISCOS Ltd licensed the rights to RISC OS from Element 14 (and eventually from the new owner, Pace Micro Technology) and continued the development of OS 3.8, releasing it as RISC OS 4 in July 1999. According to the company, over 6,400 copies of RISC OS 4.02 on ROM were sold up until production was ceased in mid-2005.
In May 2001 the company launched RISC OS Select, a subscription scheme allowing users access to the latest OS updates. These upgrades are released as soft-loadable ROM images, separate to the ROM where the boot OS is stored, and are loaded at boot time. Select 1 was shipped in May 2002, with Select 2 following in November 2002 and the final release of Select 3 in June 2004. RISCOS Ltd released the ROM based version 4.39 the same month, dubbed RISC OS Adjust as a play on the RISC OS GUI convention of calling the three mouse buttons 'Select', 'Menu' and 'Adjust'. RISCOS Ltd sold its 500th Adjust ROM in early 2006.
In October 2002, the Acorn clone Iyonix PC was released by Castle Technology. This runs RISC OS 5, a separate evolution based upon the NCOS work done by Pace for set-top boxes. In October 2006, Castle announced a source sharing license plan for elements of RISC OS 5. This Shared Source Initiative (SSI) is managed by RISC OS Open Limited.
Also in October 2006, RISCOS Ltd announced RISC OS Six, the next generation of their stream of the operating system. The first product to be launched under the name was the continuation of the Select scheme, Select 4. A beta-version of RISC OS 6, Preview 1 (Select 4i1), was available in 2007 as a free download to all subscribers to the Select scheme, while in April 2009 the final release of Select 5 was shipped.
The latest release of RISC OS from RISCOS Ltd is Select 6i1, shipped in December 2009.
Versions of RISC OS run or have run on the following hardware.
|Machine||Introduced||OEM version||ROL version||ROOL version|
|ARM with 26-bit program counter|
|Acorn Archimedes||1987 – 1992||0.30||3.1x||N/A||N/A||N/A||N/A|
|ARM with 26- & 32-bit program counter|
|Acorn Risc PC||1994||3.50||3.71||4.00||6.20||5.15||5.21|
|Acorn A7000 and A7000+||1995 – 1997||3.60||3.71||4.00||6.20||5.15||5.21|
|Acorn Phoebe||1998 (Cancelled)||3.80 (Ursula)||N/A||N/A||N/A||N/A||N/A|
|Castle Kinetic RiscPC||2000||N/A||N/A||4.03||6.20||5.19||5.21|
|Advantage Six A75||2004||N/A||N/A||4.39||N/A||N/A|
|ARM with 32-bit program counter|
|Iyonix Ltd Iyonix PC||2002||5.01||5.13||N/A||N/A||5.14||5.18/5.21|
|Advantage Six A9 (Home/RM/Loc)||2005||N/A||N/A||4.42||N/A||N/A|
|Always Innovating Touch Book||2009||N/A||N/A||N/A||N/A||5.15||5.21|
Note that RISC OS Open Limited adopted 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 can also run on a range of computer system emulators that emulate the earlier Acorn machines listed above.
|Emulator||Machines Emulated||Host Platforms Supported||Latest Release|
|Archie||Archimedes||Windows, DOS||0.9 10 February 2001|
|Arcem||Archimedes||Windows, Linux, Mac OS, RISC OS||1.50 16 December 2012|
0.99 15 August 2009
|Red Squirrel||Archimedes, Risc PC, A7000||Windows||0.6 28 October 2002|
|RPCEmu||Risc PC, A7000||Windows, Linux, Mac OS, Open BSD||0.8.10 27 March 2013|
|VirtualRPC||Risc PC||Windows, Mac OS||Update Patch 22 January 2009|
The emulator VirtualRPC is available as a standalone product or pre-bundled with Microsoft Windows PCs from Microdigital, Advantage Six and R-Comp. This emulator comes with a fully licenced copy of RISC OS – 4.02, or 4.39, depending on the version of emulator purchased.
The OS is single-user and employs cooperative multitasking (CMT). 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. The OS memory protection is not comprehensive.
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, allowing the operating system to be updated without having to replace the ROM chip. The OS is made up of a number of 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 ABIs to handle filters and vectors. The OS provides many ways in which the programmer can intercept and modify its operation. This simplifies the task of modifying its behaviour, either in the GUI or deeper. As a result, there is a number of third-party programs which allow the OS look and feel to be customised.
The file system is volume-oriented: the top level of the file hierarchy is a volume (disc, network share) prefixed by the filesystem type. To determine file type, the OS uses metadata instead of file extensions. Colons are used to separate the filesystem from the rest of the path; the root is represented by a dollar (
$) sign and directories are separated by a full stop (
.). Extensions from foreign filesystems are shown using a slash (
example/txt). For example,
ADFS::HardDisc4.$ is the root of the disc named HardDisc4 using the ADFS filesystem. RISC OS filetypes can be preserved on other systems by appending the hexadecimal type as '
,xxx' to filenames. When using cross-platform software, filetypes can be invoked on other systems by naming appending '
/[extension]' to the filename under RISC OS.
A file system can present a file of a particular type as a volume in its own right, similar to a loop device. The OS refers to this functionality 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 filesystems put a reference inside the image file and go elsewhere for the data.
Neither the file system abstraction layer, nor many RISC OS-native file systems support files larger than 2GB.
The RISC OS kernel is single-tasking (the cooperative multi-tasking is provided by the WindowManager module) and controls handling of interrupts, DMA services, memory allocation and the video display.
The WIMP interface incorporates three mouse buttons (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 behaviour. They represent the running application as a whole, irrespective of whether it has open windows.
The GUI is centred around the concept of files. The Filer 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. Application directories are used to store applications. The OS differentiates them from normal directories through the use of a pling (exclamation mark, also called 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 installation and removal.
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 's Select release in 2001.
The outline font manager provides spatial anti-aliasing of fonts, the OS being the first operating system to include such a feature, having included it since before January 1989. Since 1994, in 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.
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. Applications still being maintained by their author(s) or others have sometimes historically been amended to provide compatibility.
The introduction of the RiscPC in 1994 and its later StrongARM upgrade raised issues of incompatible code sequences and proprietary squeezing (compression). Patching of applications for the StrongARM was facilitated and Acorn's UnsqueezeAIF software unsqueezed images according to their AIF header. The incompatibilities prompted release by The ARM Club of its Game On! and StrongGuard software. They allowed some previously incompatible software to be run on new and upgraded systems. The version of the OS for the A9home prevented the running of software without an AIF header (in accordance with Application Note 295) to stop "trashing the desktop".
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. Static code analysis to detect 26-bit only sequences can be undertaken using ARMalyser. Its output can be helpful in making 32-bit versions of older applications for which the source code is unavailable. Some older 26-bit software can be run without modification using the Aemulor emulator.
- Acorn C/C++
- List of users' groups#RISC OS
- The Icon Bar
- ROX Desktop, a graphical desktop environment for the X Window System, inspired by the user interface of RISC OS
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- "Cortex-A8 port status". RISC OS Open. Retrieved 2011-01-31. "[The port includes] a modified version of the RISC OS kernel containing support for (all) Cortex-A8 CPU cores."
- Lee, Jeffrey (2 August 2011). "Have I Got Old News For You". The Icon Bar. Retrieved 28 September 2011. "[...] Willi Theiss has recently announced that he's been working on a port of RISC OS to the PandaBoard [...]"
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- ART – Acorn RISC OS
- Chris's Acorns – Risc PC
- RISC OS Six Frequently Asked Questions
- Chris's Acorns – A7000
- Chris's Acorns – A7000+
- repackaged A7000+
- Chris's Acorns – Microdigital Medi
- Chris's Acorns – Microdigital Mico
- Chris's Acorns – RiscStation R7500
- Castle reveal Kinetic to the press
- Drobe – Omega production saga continues
- – Microdigital Omega
- Drobe – A75 is ARM7500FE ruggable
- Advantage6: Thea75
- RISC OS Open: ROM image releases
- Let's get started with a Pandora port
- Virtual Acorn versions
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- Williams, Chris (26 July 2003). "Imagining RISC OS and PMT". Drobe. Retrieved 10 July 2012.
- Michael Reed Tech Book 1 – Published articles Oct 2006 – June 2008
- RISC OS Memory Protection
- Naulls, Peter (2 January 2004). "RISC OS filename translation". Drobe. Retrieved 25 April 2012.
- Emulating RISC OS under Windows
- Fitton, Gerald (August 1994), "Fireworkz for Windows", Archive (Glastonbury: Abbey Press) 7 (11): 21, OCLC 222434223
- Iyonix: MIMEMap
- Dan Ryan (13 April 2011). History of Computer Graphics: DLR Associates Series. AuthorHouse. p. 358. ISBN 978-1-4567-5115-9. Retrieved 13 June 2013.
- Mellor, Phil (23 March 2007). "An arbitrary number of possibly influential RISC OS things". The Icon Bar. Retrieved 27 September 2011. "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."
- Round, Mark (26 February 2004). "Emulating RISC OS under Windows". OSnews. OSNews. Retrieved 2011-05-12. "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."
- Ghiraddje (22 December 2009). "The RISC OS GUI". Telcontar.net. Retrieved 2011-05-12. "Only with Mac OS X did any mainstream graphical interface provide the smoothly rendered, fractionally spaced type that Acorn accomplished in 1992 or earlier."
- Reimer, Jeremy (2005-05). "A History of the GUI". ArsTechnica. Retrieved 2011-05-25. "[...] 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!"
- Holwerda, Thom (23 June 2005). "Screen Fonts: Shape Accuracy or On-Screen Readability?". OSNews. Retrieved 2011-06-13. "[...] it was RISC OS that had the first system-wide, intricate [...] font rendering in operating systems."
- Pountain, Dick (1988-12). "Screentest: Archie RISC OS". Personal Computer World. p. 154. Retrieved 2011-01-14. "[ArcDraw] can also add text in multiple sizes and fonts to a drawing (including anti-aliased fonts)"
- Acorn Computers Support Group Application Notice 253 – New features of RISC OS version 3.5
- "Application Note 295". Engineering Support Application Note. Acorn Computers. 4 October 1996. Retrieved 28 June 2012.
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- Archiology: Michael Gilbert's collection of "relics from Acorn's past"
- Arthur Lives!: a guide by Ben Jefferys
- Arthur OS Emulator
- What is RISC OS?
- Pink Noise Productions OS documentation