Turing machines can be deterministic or nondeterministic. We will consider only deterministic machines.
Unlike the other automata we have discussed, a Turing machine does not read "input." Instead, there may be (and usually are) symbols on the tape before the Turing machine begins; the Turing machine might read some, all, or none of these symbols. The initial tape may, if desired, be thought of as "input."
We have defined acceptors, which produce only a binary (accept/reject) output, and transducers, which can produce more complicated results. However, all our work so far has been with acceptors. A Turing machine also accepts or rejects its input. More importantly, the results left on the tape when the Turing machine finishes can be regarded as the "output" of the computation; thus, a Turing machine is a transducer.