Finite Automata

What does DFA consist of?

DFA consists of a finite set of states, finite set of input symbols (alphabet), a start state, a set of accepting states, a transition function, which is a mapping. These are the 5 tuples.

What is finite automaton? What is DFA? What is NFA?

Informally, it is a state diagram that comprehensively captures all possible states and transitions that a machine can take while responding to a stream or sequence of input symbols. It is a recognizer for regular languages. Deterministic Finite Automata - the machine can only exist in one state at any give time. Non-deterministic Finite Automata - The machine can exist in multiple states at the same time.

What does a DFA do on reading an input string?

Input: a word w Question: Is w acceptable by the DFA? Steps: start with the "start state" q0 for every input symbol in the sequence w do compute the next state from the current state, given the current input symbol w and the transition function If after all symbols in w are consumed, the current state is one of the accepting states (F) then accept w. Otherwise reject w.