A finite string of symbols are like q0, q1, q2... qn, where, qi ? ? is read by an automaton and is known as input word. The whole set of words is described by ?.
Continuous, Discrete, and hybrid automat:
The theory of automata usually defines the states of abstract machines but there also exist analog automata / hybrid continuous- discrete automata / continuous automata, all of these uses continuous time, analog data, or both of them.