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RISC OS is a computer
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
originally designed by
Acorn Computers Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the United Kingdom, UK, including the Acorn Electron and the Acorn Archi ...
Ltd in
Cambridge Cambridge ( ) is a university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cambridge bec ...
, England. First released in 1987, it was designed to run on the
ARM In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between th ...
chipset, which Acorn had designed concurrently for use in its new line of
Archimedes Archimedes of Syracuse (;; ) was a Greek mathematician, physicist, engineer, astronomer, and inventor from the ancient city of Syracuse in Sicily. Although few details of his life are known, he is regarded as one of the leading scientists ...
personal computers. RISC OS takes its name from the
reduced instruction set computer In computer engineering, a reduced instruction set computer (RISC) is a computer designed to simplify the individual instructions given to the computer to accomplish tasks. Compared to the instructions given to a complex instruction set comput ...
(RISC) architecture it supports. Between 1987 and 1998, RISC OS was included in every ARM-based Acorn computer model, including the Acorn Archimedes line, Acorn's R line (with
RISC iX RISC iX is a discontinued Unix operating system designed to run on a series of workstations based on the Acorn Archimedes microcomputer. Heavily based on 4.3BSD, it was initially completed in 1988, a year after Arthur but before RISC OS. It was ...
as a dual-boot option),
RiscPC The Risc PC is Acorn Computers's RISC OS/ Acorn RISC Machine computer, launched on 15 April 1994, which superseded the Acorn Archimedes. The Acorn PC card and software allows PC compatible software to be run. Like the Archimedes, the Risc PC co ...
, A7000, and prototype models such as the Acorn
NewsPad Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the United Kingdom, UK, including the Acorn Electron and the Acorn Archi ...
and Phoebe computer. A version of the OS, named
NCOS A non-commissioned officer (NCO) is a military officer who has not pursued a commission. Non-commissioned officers usually earn their position of authority by promotion through the enlisted ranks. (Non-officers, which includes most or all enli ...
, was used in
Oracle Corporation Oracle Corporation is an American multinational computer technology corporation headquartered in Austin, Texas. In 2020, Oracle was the third-largest software company in the world by revenue and market capitalization. The company sells da ...
's
Network Computer The Network Computer (or NC) was a diskless desktop computer device made by Oracle Corporation from about 1996 to 2000. The devices were designed and manufactured by an alliance, which included Sun Microsystems, IBM, and others. The devices w ...
and compatible systems. After the break-up of Acorn in 1998, development of the OS was
fork In cutlery or kitchenware, a fork (from la, furca 'pitchfork') is a utensil, now usually made of metal, whose long handle terminates in a head that branches into several narrow and often slightly curved tines with which one can spear foods ei ...
ed and continued separately by several companies, including ,
Pace Micro Technology Pace plc was a British company who developed set-top boxes (STBs), advanced residential gateways, software and services for the pay-TV and broadband services industry. Pace's customers included cable, telco, satellite and IPTV operators. The c ...
, and
Castle Technology Castle Technology Limited, named after Framlingham Castle, was a British computer company based in Cambridge, England. It began as a producer of ARM computers and manufactured the Acorn-branded range of desktop computers that run RISC OS. Fo ...
. Since then, it has been bundled with several ARM-based desktop computers such as the
Iyonix PC The Iyonix PC was an Acorn-clone personal computer sold by Castle Technology and Iyonix Ltd between 2002 and 2008. According to news site ''Slashdot'', it was the first personal computer to use Intel's XScale processor. It ran . History ...
and
A9home The A9home was a niche small-form-factor desktop computer running RISC OS Adjust32. It was officially unveiled at the 2005 Wakefield Show, and is the second commercial ARM-based RISC OS computer to run a 32-bit version of RISC OS. When the Iyoni ...
. , the OS remains forked and is independently developed by and the community. Most recent stable versions run on the ARMv3/ARMv4
RiscPC The Risc PC is Acorn Computers's RISC OS/ Acorn RISC Machine computer, launched on 15 April 1994, which superseded the Acorn Archimedes. The Acorn PC card and software allows PC compatible software to be run. Like the Archimedes, the Risc PC co ...
, the ARMv5 Iyonix,
ARMv7 ARM (stylised in lowercase as arm, formerly an acronym for Advanced RISC Machines and originally Acorn RISC Machine) is a family of reduced instruction set computer (RISC) instruction set architectures for computer processors, configured ...
Cortex-A8 The ARM Cortex-A8 is a 32-bit processor core licensed by ARM Holdings implementing the ARMv7-A architecture. Compared to the ARM11, the Cortex-A8 is a dual-issue superscalar design, achieving roughly twice the instructions per cycle. The Cort ...
processors (such as that used in the
BeagleBoard The BeagleBoard is a low-power open-source single-board computer produced by Texas Instruments in association with Digi-Key and Newark element14. The BeagleBoard was also designed with open source software development in mind, and as a way of de ...
and
Touch Book The Touch Book is a portable computing device that functions as a netbook, and a tablet computer. Designed by Always Innovating, a company situated in the city of Menlo Park, in California, USA, it was launched at the DEMO conference in March 2 ...
) and
Cortex-A9 The ARM Cortex-A9 MPCore is a 32-bit multi-core processor that provides up to 4 cache-coherent cores, each implementing the ARM v7 architecture instruction set. It was introduced in 2007. Features Key features of the Cortex-A9 core are: * ...
processors (such as that used in the
PandaBoard The PandaBoard was a low-power single-board computer development platform based on the Texas Instruments OMAP4430 system on a chip (SoC). The board has been available to the public at the subsidized price of US$174 since 27 October 2010. It is ...
) and the low-cost educational
Raspberry Pi Raspberry Pi () is a series of small single-board computers (SBCs) developed in the United Kingdom by the Raspberry Pi Foundation in association with Broadcom. The Raspberry Pi project originally leaned towards the promotion of teaching basic ...
computer. 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 The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, inste ...
(GUI) version and a
command-line interface A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...
only version (RISC OS Pico, at 3.8 MB).


History

The first version of RISC OS was originally released in 1987 as ''Arthur 1.20''. The next version, , became 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. Acorn officially halted work on the OS in January 1999, renaming themselves Element 14. In March 1999 a new company,
RISCOS Ltd RISCOS Ltd. (also referred to as ROL) was a Private company limited by guarantee, limited company engaged in computer software and IT consulting. It licensed the rights to continue the development of and to distribute it for desktop machines (as ...
, 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 A non-commissioned officer (NCO) is a military officer who has not pursued a commission. Non-commissioned officers usually earn their position of authority by promotion through the enlisted ranks. (Non-officers, which includes most or all enli ...
for use in
set-top box A set-top box (STB), also colloquially known as a cable box and historically television decoder, is an information appliance device that generally contains a TV-tuner input and displays output to a television set and an external source of sign ...
es. In 2000, as part of the acquisition of Acorn Group plc by MSDW Investment, RISC OS was sold to
Pace Micro Technology Pace plc was a British company who developed set-top boxes (STBs), advanced residential gateways, software and services for the pay-TV and broadband services industry. Pace's customers included cable, telco, satellite and IPTV operators. The c ...
, who later sold it to
Castle Technology Castle Technology Limited, named after Framlingham Castle, was a British computer company based in Cambridge, England. It began as a producer of ARM computers and manufactured the Acorn-branded range of desktop computers that run RISC OS. Fo ...
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 A ROM image, or ROM file, is a computer file which contains a copy of the data from a read-only memory chip, often from a video game cartridge, or used to contain a computer's firmware, or from an arcade game's main board. The term is frequen ...
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 Castle Technology Limited, named after Framlingham Castle, was a British computer company based in Cambridge, England. It began as a producer of ARM computers and manufactured the Acorn-branded range of desktop computers that run RISC OS. Fo ...
released the ''Acorn clone''
Iyonix PC The Iyonix PC was an Acorn-clone personal computer sold by Castle Technology and Iyonix Ltd between 2002 and 2008. According to news site ''Slashdot'', it was the first personal computer to use Intel's XScale processor. It ran . History ...
. This ran a
32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculation ...
(in contrast to
26-bit In computer architecture, 26-bit integers, memory addresses, or other data units are those that are 26 bits wide, and thus can represent unsigned values up to 67,108,863. Two examples of computer processors that featured 26-bit memory addressing ...
) variant of RISC OS, named ''RISC OS 5''. RISC OS 5 is a separate evolution of RISC OS based upon the
NCOS A non-commissioned officer (NCO) is a military officer who has not pursued a commission. Non-commissioned officers usually earn their position of authority by promotion through the enlisted ranks. (Non-officers, which includes most or all enli ...
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 The Shared Source Initiative (SSI) is a source-available software licensing scheme launched by Microsoft in May 2001. The program includes a spectrum of technologies and licenses, and most of its source code offerings are available for download aft ...
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. In December 2020, the source code of RISC OS 3.71 was leaked to The Pirate Bay.


Supported hardware

Versions of RISC OS run or have run on the following hardware. 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. A special cut down RISC OS Pico (for 16MiB cards and larger) styled to start up like a
BBC Micro The British Broadcasting Corporation Microcomputer System, or BBC Micro, is a series of microcomputers and associated peripherals designed and built by Acorn Computers in the 1980s for the BBC Computer Literacy Project. Designed with an emphas ...
was released for BASIC's 50th anniversary. RISC OS has also been used by both Acorn and
Pace Micro Technology Pace plc was a British company who developed set-top boxes (STBs), advanced residential gateways, software and services for the pay-TV and broadband services industry. Pace's customers included cable, telco, satellite and IPTV operators. The c ...
in various TV connected
set-top box A set-top box (STB), also colloquially known as a cable box and historically television decoder, is an information appliance device that generally contains a TV-tuner input and displays output to a television set and an external source of sign ...
es, sometimes referred to instead as
NCOS A non-commissioned officer (NCO) is a military officer who has not pursued a commission. Non-commissioned officers usually earn their position of authority by promotion through the enlisted ranks. (Non-officers, which includes most or all enli ...
. RISC OS can also run on a range of computer system emulators that emulate the earlier Acorn machines listed above.


Features


OS core

The OS is
single-user Multi-user software is computer software that allows access by multiple users of a computer. Time-sharing systems are multi-user systems. Most batch processing systems for mainframe computers may also be considered "multi-user", to avoid leaving t ...
and employs
cooperative multitasking Cooperative multitasking, also known as non-preemptive multitasking, is a style of computer multitasking in which the operating system never initiates a context switch from a running process to another process. Instead, in order to run multiple ...
(CMT). While most current desktop OSes use preemptive multitasking (PMT) and multithreading, remains with a CMT system. By 2003, many users had called for the OS to migrate to PMT. The OS
memory protection Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that ha ...
is not comprehensive. The core of the OS is stored in
ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...
, giving a fast
bootup In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so so ...
time and safety from operating system corruption. RISC OS 4 and 5 are stored in of
flash memory Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory, NOR flash and NAND flash, are named for the NOR and NAND logic gates. Both us ...
, or as a
ROM image A ROM image, or ROM file, is a computer file which contains a copy of the data from a read-only memory chip, often from a video game cartridge, or used to contain a computer's firmware, or from an arcade game's main board. The term is frequen ...
on
SD Card Secure Digital, officially abbreviated as SD, is a proprietary non-volatile flash memory card format developed by the SD Association (SDA) for use in portable devices. The standard was introduced in August 1999 by joint efforts between SanDis ...
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
module Module, modular and modularity may refer to the concept of modularity. They may also refer to: Computing and engineering * Modular design, the engineering discipline of designing complex devices using separately designed sub-components * Mo ...
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 In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, acc ...
s in other operating systems. Most of the OS has defined
application binary interface In computer software, an application binary interface (ABI) is an interface between two binary program modules. Often, one of these modules is a library or operating system facility, and the other is a program that is being run by a user. An ' ...
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

The
file system In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...
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 A file format is a standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary or free. Some file format ...
, the OS uses
metadata Metadata is "data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive metadata – the descriptive ...
instead of
file extension A filename extension, file name extension or file extension is a suffix to the name of a computer file (e.g., .txt, .docx, .md). The extension indicates a characteristic of the file contents or its intended use. A filename extension is typically d ...
s. Colons are used to separate the file system from the rest of the path; the root is represented by a dollar ($) sign and directories are separated by a full stop (.). Extensions from foreign file systems are shown using a slash (example.txt becomes example/txt). For example, ADFS::HardDisc4.$ is the root of the disc named ''HardDisc4'' using the
Advanced Disc Filing System The Advanced Disc Filing System (ADFS) is a computing file system unique to the Acorn computer range and RISC OS-based successors. Initially based on the rare Acorn Winchester Filing System, it was renamed to the Advanced Disc Filing System when ...
(ADFS) file system. filetypes can be preserved on other systems by appending the hexadecimal type as ',xxx' to filenames. When using
cross-platform In computing, cross-platform software (also called multi-platform software, platform-agnostic software, or platform-independent software) is computer software that is designed to work in several computing platforms. Some cross-platform software r ...
software, filetypes can be invoked on other systems by naming appending '/ xtension/code>' to the filename under . A file system can present a file of a given type as a volume of its own, similar to a
loop device In Unix-like operating systems, a loop device, vnd (vnode disk), or lofi (loop file interface) is a pseudo-device that makes a computer file accessible as a block device. Before use, a loop device must be connected to an extant file in the file sy ...
. 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
API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...
uses 32-bit file offsets, making the largest single file 4 
GiB The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...
(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 bits (just under 2 GiB) to avoid dealing with apparently negative file extents when expressed in
two's complement Two's complement is a mathematical operation to reversibly convert a positive binary number into a negative binary number with equivalent (but negative) value, using the binary digit with the greatest place value (the leftmost bit in big- endian ...
notation.


File formats

The OS uses
metadata Metadata is "data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive metadata – the descriptive ...
to distinguish
file format A file format is a standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary or free. Some file formats ...
s. Some common file formats from other systems are mapped to filetypes by the MimeMap module.


Kernel

The RISC OS kernel is single-tasking and controls handling of
interrupt In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, ...
s, DMA services, memory allocation and the video display; the cooperative multi-tasking is provided by the WindowManager module.


Desktop

The
WIMP Wimp, WIMP, or Wimps may refer to: Science and technology * Weakly interacting massive particle, a hypothetical particle of dark matter * WIMP (computing), the "window, icon, menu, pointer" paradigm * WIMP (software bundle), the web stack of Wind ...
interface is based on a
stacking window manager A stacking window manager (also called floating window manager) is a window manager that draws and allows windows to overlap, without using a compositing algorithm. All window managers that allow the overlapping of windows but are not compositing ...
and incorporates three
mouse button A mouse button is an electric switch on a computer mouse which can be pressed (“clicked”) to select or interact with an element of a graphical user interface. Mouse buttons are most commonly implemented as miniature snap-action switches ...
s (named ''Select'', ''Menu'' and ''Adjust''), context-sensitive menus, window order control (i.e. send to back) and dynamic window
focus Focus, or its plural form foci may refer to: Arts * Focus or Focus Festival, former name of the Adelaide Fringe arts festival in South Australia Film *''Focus'', a 1962 TV film starring James Whitmore * ''Focus'' (2001 film), a 2001 film based ...
(a window can have input focus at any position on the stack). The
icon bar An icon () is a religious work of art, most commonly a painting, in the cultures of the Eastern Orthodox, Oriental Orthodox, and Catholic churches. They are not simply artworks; "an icon is a sacred image used in religious devotion". The most c ...
( 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 In computer graphical user interfaces, drag and drop is a pointing device gesture in which the user selects a virtual object by "grabbing" it and dragging it to a different location or onto another virtual object. In general, it can be used to ...
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 In computing, a spatial file manager is a file manager that uses a spatial metaphor to represent files and folders as if they were real physical objects. Concepts The base requirements of a spatial file manager are: # Each folder is represe ...
, 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 The exclamation mark, , or exclamation point (American English), is a punctuation mark usually used after an interjection or exclamation to indicate strong feelings or to show emphasis. The exclamation mark often marks the end of a sentence, f ...
(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 ''Style Guide'' encourages a consistent
look and feel In software design, the look and feel of a graphical user interface comprises aspects of its design, including elements such as colors, shapes, layout, and typefaces (the "look"), as well as the behavior of dynamic elements such as buttons, boxes ...
across applications. This was introduced in 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.


Font manager

RISC OS was the first operating system to provide scalable anti-aliased fonts. Anti-aliased fonts were already familiar from Arthur, and their presence in RISC OS was confirmed in an early 1989 preview, featuring in the final RISC OS 2 product, launched in April 1989. A new version of the font manager employing "new-style outline fonts" was made available after the release of RISC OS, offering full support for the printing of scalable fonts, and was provided with Acorn Desktop Publisher. It was also made available separately and bundled with other applications. This
outline font A computer font is implemented as a digital data file containing a set of graphically related glyphs. A computer font is designed and created using a font editor. A computer font specifically designed for the computer screen, and not for print ...
manager provides support for the rendering of font outlines to bitmaps for screen and printer use, employing
anti-aliasing Anti-aliasing may refer to any of a number of techniques to combat the problems of aliasing in a sampled signal such as a digital image or digital audio recording. Specific topics in anti-aliasing include: * Anti-aliasing filter, a filter used be ...
for on-screen fonts, utilising sub-pixel anti-aliasing and caching for small font sizes. 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 System 7, codenamed "Big Bang", and also known as Mac OS 7, is a graphical user interface-based operating system for Macintosh computers and is part of the classic Mac OS series of operating systems. It was introduced on May 13, 1991, by Apple Co ...
and
OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 ...
version 2. 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. RISC OS 4 does not support
Unicode Unicode, formally The Unicode Standard,The formal version reference is is an information technology Technical standard, standard for the consistent character encoding, encoding, representation, and handling of Character (computing), text expre ...
but "RISC OS 5 provides a Unicode Font Manager which is able to display Unicode characters and accept text in
UTF-8 UTF-8 is a variable-width encoding, variable-length character encoding used for electronic communication. Defined by the Unicode Standard, the name is derived from ''Unicode'' (or ''Universal Coded Character Set'') ''Transformation Format 8-bit'' ...
, UTF-16 and UTF-32. Other parts of the RISC OS kernel and core modules support text described in UTF-8." Support for the characters of RISC OS (and some other historic computers) was added to
Unicode Unicode, formally The Unicode Standard,The formal version reference is is an information technology Technical standard, standard for the consistent character encoding, encoding, representation, and handling of Character (computing), text expre ...
13.0 (in 2020).


Bundled applications

is available in several distributions, all of which include a small standard set of
desktop application A desktop traditionally refers to: * The surface of a desk (often to distinguish office appliances that fit on a desk, such as photocopiers and printers, from larger equipment covering its own area on the floor) Desktop may refer to various compu ...
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 A computer program is said to be portable if there is very low effort required to make it run on different platforms. The pre-requirement for portability is the generalized abstraction between the application logic and system interfaces. When ...
exists with subsequent versions of the OS and hardware. Single-tasking
BBC BASIC BBC BASIC is a version of the BASIC programming language released in 1981 as the native programming language for the BBC Micro home/personal computer, providing a standardized language for a UK computer literacy project of the BBC. It was wr ...
applications often require only trivial changes, if any. Successive OS upgrades have raised more serious issues of
backward compatibility Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially i ...
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 The Risc PC is Acorn Computers's RISC OS/ Acorn RISC Machine computer, launched on 15 April 1994, which superseded the Acorn Archimedes. The Acorn PC card and software allows PC compatible software to be run. Like the Archimedes, the Risc PC co ...
in 1994 and its later
StrongARM The StrongARM is a family of computer microprocessors developed by Digital Equipment Corporation and manufactured in the late 1990s which implemented the ARM v4 instruction set architecture. It was later acquired by Intel in 1997 from DEC's o ...
upgrade raised issues of incompatible code sequences and proprietary squeezing (
data compression In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compression ...
).
Patch Patch or Patches may refer to: Arts, entertainment and media * Patch Johnson, a fictional character from ''Days of Our Lives'' * Patch (''My Little Pony''), a toy * "Patches" (Dickey Lee song), 1962 * "Patches" (Chairmen of the Board song) ...
ing of applications for the StrongARM was facilitated and Acorn's ''UnsqueezeAIF'' software unsqueezed images according to their
AIF header In computer programming, the Arm Image Format (AIF) is an object file file format, format used primarily for software intended to run on ARM architecture, ARM microprocessors. It was introduced by Acorn Computers for use with their Acorn Archimedes ...
. The incompatibilities prompted release by ''The ARM Club'' of its ''Game On!'' and ''StrongGuard'' software. They allowed some formerly incompatible software to run on new and upgraded systems. The version of the OS for the
A9home The A9home was a niche small-form-factor desktop computer running RISC OS Adjust32. It was officially unveiled at the 2005 Wakefield Show, and is the second commercial ARM-based RISC OS computer to run a 32-bit version of RISC OS. When the Iyoni ...
prevented the running of software without an AIF header (in accord with Application Note 295) to stop "trashing the desktop". The
Iyonix PC The Iyonix PC was an Acorn-clone personal computer sold by Castle Technology and Iyonix Ltd between 2002 and 2008. According to news site ''Slashdot'', it was the first personal computer to use Intel's XScale processor. It ran . History ...
() and
A9home The A9home was a niche small-form-factor desktop computer running RISC OS Adjust32. It was officially unveiled at the 2005 Wakefield Show, and is the second commercial ARM-based RISC OS computer to run a 32-bit version of RISC OS. When the Iyoni ...
(custom ) saw further software incompatibility because of the deprecated addressing modes. Most applications under active development have since been rewritten.
Static code analysis In computer science, static program analysis (or static analysis) is the analysis of computer programs performed without executing them, in contrast with dynamic program analysis, which is performed on programs during their execution. The term i ...
to detect -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 In computing, Aemulor is an emulator of the earlier addressing-mode ARM microprocessors. It runs on ARM processors under addressing-mode versions of . It was written by Adrian Lees and released in 2003. An enhanced version is available under the ...
emulator. Additional incompatibilities were introduced with newer
ARM core This is a list of central processing units based on the ARM In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) an ...
s, such as ARMv7 in the
BeagleBoard The BeagleBoard is a low-power open-source single-board computer produced by Texas Instruments in association with Digi-Key and Newark element14. The BeagleBoard was also designed with open source software development in mind, and as a way of de ...
and ARMv8 in the . This includes changes to unaligned memory access in ARMv6/v7 and removal of the SWP instructions in ARMv8.


See also

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Acorn C/C++ Acorn C/C++ is a set of C/C++ programming tools for use under the operating system. The tools use the Norcroft compiler suite and were authored by Codemist and Acorn Computers. The tools provide some facilities offered by a fully integrated dev ...
*
ArtWorks A work of art, artwork, art piece, piece of art or art object is an artistic creation of aesthetics, aesthetic value. Except for "work of art", which may be used of any work regarded as art in its widest sense, including works from ...
*
Drobe ''Drobe'' (also referred to as ''Drobe Launchpad'') was a computing news web site with a focus on the operating system. Its archived material was retained online, curated by editor Chris Williams until late 2020. History ''Drobe'' was found ...
*
ROX Desktop The ROX Desktop is a graphical desktop environment for the X Window System. It is based on the ROX-Filer which is a drag and drop spatial file manager. It is free software released under the GNU General Public License. The environment was ins ...
, a graphical desktop environment for the X Window System, inspired by the user interface of RISC OS *
Sibelius (scorewriter) Sibelius is a scorewriter program developed and released by Sibelius Software Limited (now part of Avid Technology). It is the world's largest selling music notation program. Beyond creating, editing and printing music scores, Sibelius can ...
, originally an application for RISC OS, rewritten for Windows in 1998 * RISC OS character set


References


External links

* RISC OS Open {{Operating system Acorn operating systems ARM operating systems Desktop environments Free software operating systems Software using the Apache license Window-based operating systems 1987 software