According to the project's application manager Richard Cownie, 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. 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. 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. ARX had support of a file system for optical
WORM disks) 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. 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. Confusion persisted about the nature of ARX amongst the wider public and press, with some believing that ARX was Acorn's own Unix variant, 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. ==See also==