In the theory of computation, a deterministic finite state machine or deterministic finite automaton (DFA) is a finite state machine where for each pair of state and input symbol there is one and only one transition to a next state. DFAs recognize the set of regular languages and no other languages.
A DFA will take in a string of input symbols. For each input symbol it will then transition to a state given by following a transition function. When the last input symbol has been received it will either accept or reject the string depending on whether the DFA is in an accepting state or a non-accepting state.
Reference:
http://en.wikipedia.org/wiki/Deterministic_finite_automaton
