The really short answer is that computers do not have two kinds of storage any more. It used to be that you had the primary store, and it was anything from acoustic delaylines filled with mercury via small magnetic dougnuts via transistor flip-flops to dynamic RAM. And then there were the secondary store, paper tape, magnetic tape, disk drives the size of houses, then the size of washing machines and these days so small that girls get disappointed if think they got hold of something else than the MP3 player you had in your pocket. And people program this way.

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