Ø    The finite automata is called deterministic finite automata, if there is only one path for specific input from current state to next state. Ø    In DFA, for each input symbol, one can determine the state which machine will move. Ø    As it has finite number of states, the machine is called deterministic finite machine or deterministic finite automata Graphical Representation: Ø    A DFA is represented by digraphs called state diagram or transition diagram   the vertices represent the states Ø    The arcs/ edges labelled with an input symbols shows the transitions Ø    Initial state is denoted by single circle and arrow pointing towards it(i.e. incoming arrow) Ø    The final state is denoted by two concentric circles Formal definition of DFA: Ø    A DFA can be represented by  5 -tuple or Quintuple machine M= (Q, ∑, δ, q 0 , F),  where − ·       Q  is a finite set of states. ·       ∑  is a finite set of symbols, called the   input   alphabet  of the a