Whats wrong with Atari TOS? It was a minimalist approach as far as operating systems go. But thats really how it should be, with the OS doing its job quietly in the background managing resources with the user having ultimate control. Contrast with Windows where the opposite is true; OS is a constant, overbearing nag, assuming every conceivable function, user control contingent upon mastery of arcane registry functions or through costly "certification". Plus, Atari at least had the decency to put the OS where it belongs: in ROM.