| ARX | |
|---|---|
| Developer | Acorn Computers Ltd. |
| Written in | Modula-2+ |
| OS family | Unix-like |
| Working state | Discontinued |
| Marketing target | Low cost paperless office computing workstation |
| Available in | English |
| Supported platforms | ARM |
| Kernel type | Microkernel |
| Default user interface | Graphical user interface1 and special keyboard keys2 |
| License | Proprietary |
| Preceded by | MOS |
| Succeeded by | Arthur, renamed RISC OS |
ARX was an unreleased Mach-like operating system written in Modula-2+3 developed by Acorn Computers Ltd in the Acorn Research Centre in Palo Alto for Acorn's new Archimedes personal computers based on the ARM architecture RISC CPUs. Later stages of development were continued by Olivetti after it acquired Acorn, before the project was cancelled and replaced.
Overview
According to the project's application manager Richard Cownie4, while Acorn was developing the kernel, it used CAMEL, the C and Acorn Modula Execution Library, with the Acorn Extended Modula-2 (AEM2) compiler, ported from ETH Modula-2. Though never released externally, CAMEL was ported to use on Sun Microsystems Unix computers.5 In an effort to port Sun's NeWS to the Archimedes, David Chase developed a compiler based on AEM2 for the programming language Modula-3.6
ARX was a preemptive multitasking, multithreading, multi-user operating system. Much of the OS ran in user mode and as a result suffered performance problems due to switches into kernel mode to perform mutexes, which led to the introduction of the SWP instruction to the ARM2 v2a instruction set.7 ARX had support of a file system for optical WORM disks4 and featured a window system, a window toolkit (and a direct manipulation user interface (UI) editor8) and an Interscript-based text editor, for enriched documents written in Interpress (a HTML precursor). The OS had to fit in a 512 KB ROM.9
ARX was not finished in time to be used in the Acorn Archimedes range of computers, which shipped in 1987 with an operating system named Arthur. Later renamed RISC OS, this was derived from Acorn MOS as used in the company's earlier BBC Micro range.10 Confusion persisted about the nature of ARX amongst the wider public and press, with some believing that ARX was Acorn's own Unix variant,11 with this view being refined in time to accommodate ARX as Acorn's own attempt to deliver a "UNIX look-alike" whose development had been abandoned in favour of a traditional Unix version for the Archimedes, which ultimately emerged as RISC iX.12
References
References
- "Acorn History (untitled)". Retrieved 2010-12-26.
- "Chris's Acorns: Acorn A500 (prototype)". Retrieved 2022-12-19.
- Bruce, Cockburn. "Aha—what about Modula-2?". Usenet post to comp.sys.acorn detailing the relationship between ARX and Modula-2
- TOP3 smart moves Richard Cownie. Real World Technologies (September 2009)
- Chase, David. "David Chase (resume)". Retrieved 2015-10-25.
- Jordan, Mick (1990). "An extensible programming environment for Modula-3" (PDF). ACM SIGSOFT Software Engineering Notes. 15 (6): 66–76. doi:10.1145/99278.99285. Retrieved 2009-09-08.
- Bowler, John (16 August 1991). "Re: Multiprocessing Archimedes??". Newsgroup: comp.sys.acorn. Retrieved 24 May 2026.
- "Brian T. Lewis - Resume". Archived from the original on 2004-05-01. Retrieved 2010-12-26.
- "Full Acorn Machine List". Retrieved 2010-12-27.
- Holgate, Chris; Davison, Rob; Burke, Stephen; Given, David; Harris, Ben; Kendrick, Rob; Bracey, Kevin; Fenelon, Pete; Blunt, Terry; druck; Markettos, Theo; Kossow, Al; Zuschlag, Jesper; Barclay, Alan; Crocker, Stephen; Pampling, Steven; et al. "Not A RISC By Thursday". Neil Franklin's Usenet Archive. Retrieved 2020-02-07. A set of Usenet posts detailing why ARX was abandoned for RISC OS.
- "Fact or fantasy?". Archive. February 1988. p. 50. Retrieved 30 April 2021.
- "PC Emulator and Arthur". RISC User. September 1988. p. 44. Retrieved 30 April 2021.