Abstract: A method of enabling multiple different operating systems to run concurrently on the same RISC (e.g. ARM) computer, comprising selecting a first operating system to have a relatively high priority (the realtime operating system, such as C5); selecting at least one secondary operating system to have a relatively lower priority (the general purpose operating system, such as Linux); providing a common program (a hardware resource dispatcher similar to a nanokernel) arranged to switch between said operating systems under predetermined conditions; and providing modifications to said first and second operating systems to allow them to be controlled by said common program.