In 1987, as the first reduced instruction set computing (RISC) ARM chips hit the scene, programmers at Acorn Computers created RISC OS, a simple, ‘co-operatively multi-tasked’ OS designed for small computing environments. While it’s no Linux, it’s still a great way to get to know RISC computing and, more important, it boots fast and has a working GUI. Now, according to a post on Rasberrypi.org, it’s available for download for all Pi users.