Editing ARX (operating system) (section)

==Overview==
According to the project Application Manager<ref name=AppManagRCAc>[https://www.realworldtech.com/forum/?threadid=96764&curpostid=96801 TOP3 smart moves]  Richard Cownie. Real World Technologies (September 2009)</ref> Richard Cownie, during the project, while Acorn was developing the kernel, it used the C and Acorn Modula Execution Library (CAMEL) in the  Acorn Extended Modula-2 (AEM2) compiler (ported from [[Modula-2]] [[ETH Zurich]] (ETH) using [[Econet]] hardware). Though never released externally, CAMEL was ported to use on [[Sun Microsystems]] Unix computers.<ref name=HMCDCR>{{Cite web
| url=http://chasewoerner.org/resume.html
| title=David Chase (resume)
| last=Chase |first=David
| access-date=2015-10-25
}}</ref> In an effort to port Sun's [[workstation]]s Sun [[NeWS]] to the Archimedes, David Chase developed a compiler based on AEM2 for the programming language [[Modula-3]].<ref>{{Cite journal
| doi = 10.1145/99278.99285
| volume = 15
| issue = 6
| pages = 66–76
| last = Jordan
| first = Mick
| title = An extensible programming environment for Modula-3
| journal = SIGSOFT Software Engineering Notes
| access-date = 2009-09-08
| year = 1990
| url = https://www.cs.tufts.edu/~nr/cs257/archive/mick-jordan/modula-3-environment.pdf
}}</ref>

ARX was a [[Preemption (computing)|preemptive]] [[computer multitasking|multitasking]], [[Thread (computing)|multithreading]], multi-user [[operating system]]. Much of the OS ran in [[User space|user mode]] and as a result suffered performance problems due to switches into [[Protection ring#Supervisor mode|kernel mode]] to perform [[Lock (computer science)|mutexes]], which led to the introduction of the SWP instruction to the instruction set of the ARMv2a version of the ARM processor. It had support of a file system for optical ([[write once read many]] (WORM)) disks<ref name=AppManagRCAc /> and featured a window system, a window toolkit (and a direct manipulation [[user interface]] (UI) editor<ref name=BTLTSARC>{{Cite web
 |title=Brian T. Lewis - Resume 
 |access-date=2010-12-26 
 |url=http://pages.sbcglobal.net/btlewis/resume-formatted.html
|archive-url=https://web.archive.org/web/20040501210222/http://pages.sbcglobal.net/btlewis/resume-formatted.html
|url-status=dead
|archive-date=2004-05-01
}}</ref>) and an [[Interscript]]-based text editor, for enriched documents written in [[Interpress]] (a [[HTML]] precursor). The OS had to be fitted in a 512&nbsp;[[Kilobyte|KB]] [[read-only memory]] (ROM) [[ROM image]].<ref name=FAMLA500>{{Cite web
| title=Full Acorn Machine List
| access-date=2010-12-27
| url=http://www.khantazi.org/Archives/MachineLst.html#A500
}}</ref> This suggests that ARX had a [[microkernel]]-type design.{{According to whom|date=April 2021}}

It 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]], derived from the earlier [[Acorn MOS|Machine Operating System]] (MOS) from Acorn's earlier [[8-bit]] [[BBC Micro]] range.<ref>{{Cite web |url=http://neil.franklin.ch/Usenet/alt.folklore.computers/20010824_Not_A_RISC_By_Thursday |title=Not A RISC By Thursday |last1=Holgate |first1=Chris |last2=Davison |first2=Rob |last3=Burke |first3=Stephen |last4=Given |first4=David |last5=Harris |first5=Ben |last6=Kendrick |first6=Rob |last7=Bracey |first7=Kevin |last8=Fenelon |first8=Pete |last9=Blunt |first9=Terry |author10=druck |last11=Markettos |first11=Theo |last12=Kossow |first12=Al |last13=Zuschlag |first13=Jesper |last14=Barclay |first14=Alan |last15=Crocker |first15=Stephen |last16=Pampling |first16=Steven |display-authors=et al. |website=Neil Franklin's Usenet Archive |access-date=2020-02-07}} A set of Usenet posts detailing why ARX was abandoned for RISC OS.</ref> Confusion persisted about the nature of ARX amongst the wider public and press, with some believing that ARX was Acorn's own Unix variant,<ref name="archive198802">{{ cite news | url=https://archive.org/details/Archive_1988-02_OCR/page/n51/mode/1up | title=Fact or fantasy? | work=Archive | date=February 1988 | access-date=30 April 2021 | pages=50 }}</ref> 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]].<ref name="riscuser198809">{{ cite news | url=https://archive.org/details/eu_RiscUser_1988-09_OCR/page/n43/mode/1up | title=PC Emulator and Arthur | work=RISC User | date=September 1988 | access-date=30 April 2021 | pages=44 }}</ref>

The Acorn Research Centre was acquired by [[Olivetti]].