For ARM RasPi1-3, RasPi Zero etc there is Risc OS https://www.riscosopen.org https://www.riscosopen.org From https://www.raspberrypi.org/forums/viewtopic.php?f

For ARM RasPi1-3, RasPi Zero etc there is Risc OS https://www.riscosopen.org https://www.riscosopen.org From https://www.raspberrypi.org/forums/viewtopic.php?f=55&t=22093 https://www.raspberrypi.org/forums/viewtopic.php?f=55&t=2209... : What is RISC OS? RISC OS is a new and different OS for the Pi. It isn't Linux, it isn't Unix, it isn't based on any other OS. It's the first ARM OS, begun in 1987 by the team who designed the original ARM processor. It's also a descendant of the OS used on the early 1980s BBC Micro... those who remember the BBC Micro might find some of its commands familiar. BBC BASIC is only a few keypresses away. What's interesting about RISC OS? It's small. It's fast. RISC OS is a full desktop OS, where the core system including windowing system and a few apps fits inside 6MB. It was developed at a time when the fastest desktop computer was an 8MHz ARM2 with 512KB of RAM. That means it's fast and responsive on modern hardware. The memory taken by apps is usually counted in the kilobytes. A 700MHz 256MB Raspberry Pi is luxury - what to do with all that memory? RISC OS is also a lot simpler than modern OSes such as Linux. The pace of development has been a little slower than other OSes, which means there are fewer layers getting between you and the system. It's much easier to get stuck in and change things. It's also easier to understand. As a formerly closed-source OS, most of the interfaces are documented in a series of books called the Programmers' Reference Manuals (PRMs) which are included on the RISC OS Pi distro. That means you can change a lot of things without having to work on the OS code itself (which is available if you want it). It's very modular, so you can mix and match components, and the communications between modules are carefully documented. RISC OS gets out of the way. It's a 'co-operatively multi-tasked' OS. While that means one misbehaving application can stall the system until you kill it, it also means you easily write apps that take over the whole machine - for example controlling hardware where you need predictable timing. RISC OS is a single-user OS, which means there's very little security - not great for internet banking, but very handy when you want to dig around and program the internals of the OS. As a full desktop OS, there's also plenty of traditional desktop software available like drawing programs and desktop publishers. Features you've come to expect on a desktop like scalable fonts and printing are supported. RISC OS was big in UK education in the 1990s, and there's a large back catalogue of educational software.