Turing machines don't have to be deterministic (though it doesn't let you in principle calculate things you otherwise couldn't): https://en.wikipedia.org/wiki/N

Turing machines don't have to be deterministic (though it doesn't let you in principle calculate things you otherwise couldn't): https://en.wikipedia.org/wiki/Nondeterministic_Turing_machine https://en.wikipedia.org/wiki/Nondeterministic_Turing_machin..., https://en.wikipedia.org/wiki/Probabilistic_Turing_machine https://en.wikipedia.org/wiki/Probabilistic_Turing_machine