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You've presented a conscientious criterion for what can be classified as an operating system. I think it's clever, I'm not sure I agree though. It's very broad: By this same definition any processor is an operating system, since it will execute arbitrary binary data. Your example of the JVM being an operating system calls to mind the above: It is a virtual machine, it is designed to execute arbitrary bytecode in a similar manner to a processor.

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You may have found a loophole in my specification :) I’d like to amend it to specify that an OS refers to software “that can run...”. (And this is why we do design reviews!).

In your example, a real or virtual machine’s load/setregs interface is an operating system. One that can only run a single program at a time in the case of the physical processor’s bootstrap, but you’d be surprised how similar that is to early DOS.

A more hand-waving version is “the lowest level interface over the machine that can run...”. So a processor and a ROM grid can run arbitrary programs, but the lowest common denominator entry point is the ROM flashing spec! A very slow scheduler indeed.

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