GavinW wrote:To understand the possibilities of SWIs you really need the Programmer's Reference Manuals. Ultimately, it is possible for users to extend RISC OS with their own modules.
Agreed, in fact RISC OS' predecessor (Arthur) didn't multitask - this feature was added as part of the WindowManager module that came in with RISC OS. New hardware gets supported by new Relocatable Modules being added (or by altering the existing modules - or intercepting the software vectors they use to enhance/modify their behaviours).
If you have RISC OS running - just press the <F12>
key to get the command prompt up - and type MODULES and press return - what you're looking at is RISC OS and the myriad modules (both internal and soft loaded 3rd party stuff) that makes the system as adaptable as it is.