Conjures up a mental image of a computer where the only mutable state is instruction pointers for parallel threads. Not quite accurate, but a rough ballpark to

Conjures up a mental image of a computer where the only mutable state is instruction pointers for parallel threads. Not quite accurate, but a rough ballpark to how crazy those "programs" must be. (If for some reason we had to work with that kind of computer we'd probably enforce a conventional, graspable approach on it by finding a way to simulate a conventional computer once and then conveniently forget about the underlying madness, clearly that wouldn't be the path taken by evolution)