Risc OS Operating System

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RiscOS Screenshot The Reduced Instruction Set Computer operating system was first used in Acorn Archimedes computers in 1987. Acorn Computers Ltd. developed her own 32-bit RISC processor, the Acorn Risc Machine (ARM), to fulfil her needings. ARM processors do not need an active fan because they have a very little power assumption in opposite to x86 processors and a much lower thermal heating.

RISC OS needs only a ROM and is protected from data damage (e.g. by viruses) reliably. Compared with most other operating systems this is an special feature. To upgrade the operating system the OS ROMs got simply replaced, newer RISC OS Computers have FlashROMs and can be upgraded to the newest stand without hardware interaction.

Pace Micro Technology plc is owner of RISC OS latest since 1999 and has handed over the further development to the company RISCOS Ltd. by now. This firm develops new software releases. Within the last 13 years RISC OS was developed intensively and is used in leading computer models of Castle Technology, RiscStation and MicroDigital.

The fields of application of RISC OS lie obviously in the graphic industry, word processing and the education market. Numerous ported programming languages are available for the development of new applications. An ambitious project pursues www.explan.co.uk with high economic computers and RISC OS for use in developing countries. A9home is a good example of the energy-saving and compact design of a complete computer. The energy consumption is covered with 2 to 3 watt. A 400 MHz Samsung ARM9 processor is used, 128 mbyte SDRAM, 8 mbyte VRAM and a 40 GByte hard disk drive.

Update: 2003-04-07
Castle Technology Ltd. takes over Pace Micro Technology plc. with the whole RISC OS technology. In addition, Castle came in a joint venture with Tematic Ltd. to develop an embedded version of RISC OS.

Update 2007-05-19
The company Castle Technology published first parts of the source code of RISC OS 5.12 for ARM architecture on the web site www.riscosopen.org, this is protected by a own shared source licence.

System Features

RISC OS is a special and efficient operating system. Many hardware and software functions became differently in comparison with Mac OS/Apple Mac or Windows/IBM PC, however, this does not derive direct disadvantages. Driver software for extensions are integrated in the ROM and can be tied by Plug & play in the operating system. In the daily usage it behaves very stably since it was tested extensively and has proved itself worldwide. Not at least the narrow coupling of the operating system to the computer provides the perfect cooperation. If nevertheless once an application should crash, it can be removed from memory without complete system crash.

The source code was written manually in large parts and optimized for the ARM. RISC OS needs only 4 MB of storage in the ROM, the extension with a fixed disk as well as creating of virtual RAM disks is possible. Moreover, to protect the system, the CMOS RAM and the fixed disk can be protected by a password to avoid changes. The booting procedure after a cold start takes fewer than 30 seconds. You can select between the BBC BASIC mode, desktop mode and command line as Shell.

RISC OS is modularized and supports software modules which can be added to the system. The multitasking GUI has been standard for the RISC OS for 13 years because of the very user friendly and effectively in this daily use. With the-bitmap optimized printing manager makes very good print results, character fonts are smoothed with anti-aliasing. Standard applications on every RISC OS are Edit for word processing, Paint for-bitmap pcitures and Draw for vector pictures which are based on up to 24-bit color resolution.

16-bit Sound support are included as well as the native support of long file names. The file management allows storing of arbitrary many files in directories. Special character like "/ ! $ Dollar %" are useable for file names without restrictions. With a 3-key mouse they can be made versatile interactions on the desktop possible, so e.g. menus are invoked comfortably with the middle mouse button in all windows. The windows and the desktop supports general Drag & Drop just like the clipboard applies to the complete system. RISC OS os is flexible, the complete system configurations can be done on the command line.

Compact applications like EasiWriter Professional+, comparably with Microsoft Word, needs only 1,101 Kbyte of storage and 860 Kbyte of RAM. Temporary files are never needed and created. Moreover, RISC OS supports DPMS (Display Power Management Signalling) and offers with the built-in programming language BBC BASIC the own ARM assembler. The simple TCP/IP support opens the Internet to the user.


RISC OS 4 - Logo
- Browser with HTML 3.2, CSS, SVG, JavaScript, Flash
- Supports FAT, ADFS, ISO9660, further FS are reloadable
- 26-bit addressing prevents the use of newer 32-bit CPUs
- Virtual memory addressing only by additional software
- dynamic storage management
- Microkernel, modularized code blocks
- only cooperative multitasking
- manages files after type not after extension
- no multithreading possible
- only few games available
- no Unicode support


Risc OS Operating System screenshot 1Risc OS Operating System screenshot 2Risc OS Operating System screenshot 3Risc OS Operating System screenshot 4
RISC OS 4 - Configuration and command lineRISC OS 4 - Internet abilitys with e-mail, news reader and browserRISC OS 4 - Artworks Vector program and Techwriter Word processingRISC OS 4 - Desktop-Theme Aqua, program window, window menu and Task overview


Date - Version
1987 - code name Arthur, programmed complete in BBC Basic
1988 - RISC OS 2 pre-version of RISC OS with size of 512 kbyte
1992 - RISC OS 3 2 mbyte in size, Programs directly in ROM integrated
1994 - RISC OS 3.5 first version for the Risc PC
1995 - RISC OS 3.6 4 mbyte in size, larger harddisk support, extended network abilities
1996 - RISC OS 3.7 support for StrongARM CPU
1999 - RISC OS 4 optimized performance (40%), new Filer
2001 - RISC OS 4+ various small improvements
2002 - RISC OS 4.32 Select 2 Beta
2003 - RISC OS 4.36 Select 3, Kernel 6.45
2004 June - RISC OS 4.39
2005 Sept. - RISC OS 5.10
2006 Feb. - RISC OS 5.11, bug fixes and a actually recompiled and optimized ROM Image of the Norcroft C/C++ compiler
2006 Nov. - RISC OS 6 Preview
2007 April - RISC OS 6.06, RISC OS Select 4i2
2008 April - RISC OS 6.10, RISC OS Select 4i4


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