Introduction to RISC OS


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This page is intended for users that are new to the RISC OS platform, but are familiar with other operating systems, and would like a quick introduction to using RISC OS. Some users may be trying the OS in emulation or on a used machine, and there may be insufficient documentation included. The focus of this article is on RISC OS 4 and newer, as much of the software available currently requires it.

However, this page is not intended to be a substitute for proper user's manuals.


Ways to run RISC OS


RISC OS development has forked into two version of RISC OS, with RISCOS Ltd. developing RISC OS 4.xx and 6.xx and Castle Technology and RISC OS Open working on RISC OS 5.xx.

RISCOS Ltd are the developers of all versions of RISC OS 4, RISC OS 4.02 is the standard with most pre-Iyonix RISC OS computers, such as the A7000+, RiscPC, R7500, Mico and Omega. These machines can be upgraded to the latest version of RISC OS, RISC OS Six (6.20). Unlike most previous versions of RISC OS, 6.20 must be softloaded, meaning that the user must have a physical ROM copy of RISC OS 4 running. Computers running VirtualAcorn come with RISC OS 4 or Adjust (4.39) installed, meaning that it can be upgraded to Six. The A9Home runs a 32-bit version of RISC OS 4, 4.42 to be exact although RISC OS Six cannot officially run on top of it at this present time.

RISC OS Open are the developers of RISC OS 5, orginally developed by the creators of the Iyonix, Castle Technology. RISC OS 5 is the open-source version of RISC OS, meaning that the general public can freely browse the RISC OS 5 code and even get involved through RISC OS Open. The latest unstable version of RISC OS 5 is 5.17, with 5.16 being the stable version. RISC OS 5.16 can be run on an Iyonix, VirtualAcorn, BeagleBoard and ARMini, with the latter being shipped with it pre-installed. RISC OS 5.16 can be run 26-bit RISC OS computers, such as the RiscPC, A7000+, Omega etc. These versions are not completely tested on those machines and are considered unstable.

Real hardware

At this time, there are a number of practical options for running RISC OS on real hardware. Developers are working on porting RISC OS to new hardware as part of the RISC OS Open project, currently they have RISC OS 5.17 running on a Do-It-Yourself Beagleboard kit, available rather cheaply online.

Acorn RiscPC

The Acorn RiscPC is a popular option for running RISC OS, due to its wide availability and expandability. However, it is the oldest and slowest machine considered acceptable for use today. Also, it has been out of production for several years.

Machines with a StrongARM processor are greatly preferred over machines with ARM610 or ARM710 processors.

Make sure that a working mouse is included, or purchase a PS/2 mouse adapter such as the PS2MouseMini. Also, if you plan on accessing a home network or broadband Internet access using a RiscPC, you will need a machine with an ethernet card installed, or you will need to install an ethernet card yourself.

These notes also apply to the Acorn A7000 and A7000+, although those machines are generally considered too slow today, as they are based on a variant of the ARM710 processor. (They do not need a special mouse, however, as they have a PS/2 mouse port.)

These machines can run any version of RISC OS from 3.50 to 3.71, 4.00 through 4.39, or 6.02 through 6.20. StrongARM machines require at least 3.70.

Some versions of the OS are stored in physical ROM chips inside the computer, whereas others use an older version to start the machine, and then load the new version from the hard drive.

If you have a machine with RISC OS 3.60, 3.70, or 3.71 ROMs installed, you can purchase a CD from RISCOS Ltd. which will upgrade your machine to RISC OS 4.02. As of this writing, the CD costs UK£20. However, you will not get some of the benefits of 4.02, including long file names, and the ability to have more than 77 files in one directory.

To get those benefits, you will need a RISC OS 4.02 ROM upgrade, which RISCOS Ltd. sells for UK£25.

If you have a machine with RISC OS 4.02 ROMs installed, or you have upgraded your ROMs, you can upgrade to either RISC OS 4.39, using the same UK£20 CD mentioned earlier, or you can upgrade to a version of RISC OS 6, starting at UK£49, also from RISCOS Ltd.

Castle IYONIX pc

The IYONIX pc is the fastest RISC OS machine that has been sold to date. It is a fully 32-bit machine, and can be upgraded to the highest specification out of any RISC OS machine currently available. However, it has been discontinued for just over a year as of this writing.

These machines come with various versions of RISC OS 5 in easily upgradeable Flash ROM. As a result of the RISC OS Open project, a free release of RISC OS 5.28 has been made available for all IYONIX users.

Advantage Six A9home

The A9home is the only RISC OS machine that is still available to purchase new. It is not as fast, nor as expandable as the IYONIX, but it is faster than the RiscPC, and it is fully 32-bit.

The versions of RISC OS used on the A9home are developed by RISCOS Ltd., and are based on 4.39. The latest version available is 4.42, and most machines have this version. RISCOS Ltd. have announced plans to release a RISC OS 6 version for the A9home.

R-Comp ARMini

Released in 2011, the R-Comp ARMini is a fully 32-bit computer system running RISC OS 5.16, the latest open-source version of RISC OS from RISC OS Open. With Advantage Six' A9Home still available to be purchased new, the ARMini is the second complete RISC OS system available to buy new on the market. Although the A9Home is considerably older than the ARMini, it should not be discounted as both machines have been produced for different purposes and excell at different tasks. Versions of RISC OS developed by RISCOS Ltd will currently not run on the ARMini, but work is underway to change this.



RPCEmu is an open source emulator of the RiscPC and A7000 hardware, able to run on Linux, Mac OS X, and Windows. This emulator is freely available, and a version of it known as RPCEmu Spoon Edition is actively maintained. RPCEmu, although feature-rich, is not a complete RISC OS emulator, if you desire a fully running RISC OS emulator for Mac or Windows, consider VirtualAcorn.

This emulator works best with RISC OS 4.02 and 4.39. RISCOS Ltd. sells a version of RISC OS 4.02 intended for use with emulators for UK£5.


VirtualAcorn is a commercial product emulating the RiscPC and A7000. It runs on Windows and Mac OS X. A version of RISC OS (either 4.02 or 4.39) is included with the emulator, complete with some applications. VirtualAcorn is to be considered if you wish for a fully complete RISC OS system running on a PC or Mac, if not, you may wish to consider RPCEmu. You can also run RISC OS 6 on top of the included OS.


Now that you've got something to run RISC OS on, let's go over how to use the platform. Even if you're familiar with another platform such as Windows, Mac OS X, or Linux, RISC OS behaves differently in some ways.

First, let's take a quick look at a typical screen that you'll see in RISC OS.

RISC OS 4.02 screenshot

This screenshot was taken in RISC OS 4.02, on RPCEmu. Your system may have different drives available, and different programs may be running.

Before explaining what you're seeing, it would be a good idea to explain how the mouse works on RISC OS, as this is important for understanding the rest of the user interface.

The mouse

RISC OS uses the mouse buttons somewhat differently from other platforms.

All mice on RISC OS machines have three buttons. However, most wheel mice do have three buttons, as the wheel acts as a middle button.

The left mouse button is named "Select," which is a self-explanatory name. For the most part, Select is used just like the left button on other platforms.

The middle mouse button is named "Menu," which is also self-explanatory. RISC OS programs don't have menu bars like applications on Windows and Linux, and there is not a system menu bar like Mac OS. All menus are context-sensitive, and are accessed by clicking the Menu button on the object that you want to manipulate.

The right mouse button is named "Adjust." Adjust normally performs a related, but different function to Select. For example, double-clicking on a folder using Select will open the folder, as will double-clicking using Adjust. However, double-clicking with Adjust closes the parent folder. An extensive list of functions that Adjust does is outside of the scope of this page, however, and you would be best served by finding a comprehensive RISC OS reference.

For future reference, "clicking" may be considered as equivalent to "Select-clicking" or "left-clicking." "Menu-clicking" is equivalent to "middle-clicking," and "Adjust-clicking" is equivalent to "right-clicking."

The icon bar

Now that we've discussed the mouse, it's time to discuss what you're seeing.

The icon bar, on the bottom of the screen, is one of the most prominent features of the RISC OS user interface, as you see it as soon as the machine is booted up, and it may be the only item on the screen.

On the left side of the icon bar, RISC OS displays items such as your drives, printers, ROM application folder, and such. If you use an emulator, your HostFS drive, which is a folder on your real computer, will also display. This allows you to copy files back and forth between RISC OS and your PC.

Clicking on a drive or folder will open its contents in the Filer. You can also Menu-click on an object here to get a menu of commands and options related to that object.

On the right side of the icon bar, applications display their icons. The Task Manager always displays at the far right, and several important functions are in its menu. The Display Manager allows changing video settings temporarily, and is to the left of the Task Manager.

To the left of that, any applications that you start up may display their icons. (Some applications don't display an icon bar icon, but almost all will.) In the screenshot above, Paint (a simple bitmap graphics editor) and Edit (a text editor) are running.

For applications that don't work with multiple documents at once, clicking on the icon bar icon will bring the application's window to the front.

However, if an application does work with multiple documents, the behavior is different. Rather than switching to the application, as most OSes do today, the application will open a new document.

And, of course, you can Menu-click on an icon bar icon to get further commands and options related to the program, including an option to exit the program.

File handling

RISC OS does not have traditional file open and save dialog boxes, unlike other platforms. RISC OS has very strong support for drag and drop, and one demonstration of this is how it handles opening and saving files.

Opening files

If a file is associated with a program, double-clicking on that file will open the program if necessary, and then open the document.

However, if you wish to open the file in another program, or it's not associated to a program, you can simply drag the file from the Filer to the application, and it will open.

Saving files

When you want to save a file, menu-click in the document window, and move the mouse pointer to Save. You will see the following (the file name and icon may be different, depending on the program you are using:)


While you may be tempted to enter a filename and click OK, this won't tell the OS where you want to save the file, and it'll tell you that you need to drag the icon to the folder that you wish to save it to. You can also enter a full pathname, but normally the best option is to do exactly what it says - drag it to a folder.

Other things this lets you do

You may be familiar with the concept of named pipes, which allow you to pipe the output of one program to the input of another program. RISC OS has a similar mechanism, made possible by its drag and drop support. Simply go to save a file, and rather than drag the icon to a folder in the filer, drag it to the icon bar icon for the program that you wish to send it to.

Window behavior

There are a couple of notes with how RISC OS handles windows that are important to mention.

First, RISC OS does not provide an Alt-Tab or similar facility to switch windows. To switch to a window that is not visible, you will have to send all windows that are on top of it to the back of the window stack, or move them out of the way. On the left side of the title bar, there are two buttons - one shows an icon of overlapping windows, the second is a close button. Click the overlapping windows button, and the window will be sent to the back of the window stack.

Second, the toggle size button (similar to maximize button in other systems) in RISC OS doesn't necessarily maximize the window to full screen. It only enlarges it to the largest size necessary, much like how Mac OS X handles maximizing windows. As the name suggests, once a window is at its maximum size, the toggle size button will reduce it back to the previous size.

RISC OS 4 introduced an optional (user configured) iconise button which will normally hide a window and place an icon representing that window on the RISC OS Pinboard (the large grey area in the screen shot above). This feature is similar to the minimise feature that users of other systems will be familiar with. Older versions of RISC OS, or those without this icon configured, achieved the same result by Shift-clicking on the Close icon of the window.

RISC OS windows may have horizontal and vertical scrollbars as required. When either of these are present, the bottom right most icon of the window is the resize icon which, as its name sounds, allows windows to be resized.

Finally, RISC OS allows a window to have focus while it is not on top. This can be useful, but is a behavior that you have to watch out for. To bring a window to the top, you must click on the title bar (or the resize or toggle size icons if present), not just within the window.

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