RISC OS is the operating system of choice for thousands of users around the world. Yet, many people have never even heard of it. I guess those who HAVE used it know how pleasurable and productive it's use can be, whereas those who have yet to experience it for themselves continue to think computers are bad, unreliable things that keep going wrong or doing things you don't want them to do.
RISC OS was the revolutionary operating system devised by Acorn, back in 1987 to power the world's first ARM based personal computers (despite what Apple claimed at the time!). Yes, Acorn were also the inventors of the ARM (Acorn Risc Machine) chip, which is arguably the most abundant micro processor in the world today, powering thousands of devices from mobile phones, personal electronic organisers and printers to desktop computers and video game consoles. To this end, RISC OS is the only operating system which allows you to learn ARM machine code programming 'out of the box' with no additional tools or software.