(Reduced Instruction Set Computer Operating System) Acorn
Computers' operating system for their Archimedes family
of personal computers. RISC OS replaced the Arthur
operating system used on the first Archimedeses. It is
written in ARMassembly code and distributed on ROM so
it takes up no disk space and takes no time to load. It
supports cooperative multitasking with memory management and
includes a graphical user interface or "WIMP". It is
written in a highly modular style and makes extensive use of
vectors so it is easy to modify and extend by loading new
modules in RAM. A large number of system calls (called
"SWIs" - software interrupts) are available to the
applications programmer and some of these are available as
user comands via a built-in command-line interpreter. RISC
OS also supported outline fonts when only bitmap fonts
were available on most other platforms.
