Question

What are the rules for constructing a deterministic finite automata in the form of a diagram? My professor explained by examples, but I am not exactly sure what rules must be followed by all diagrams. Any help is appreciated, thanks!

Answer 1

Off the top of my head, in a DFA, these are the main rules, (terms specific to DFAs are in double quotes):-

• each “state” must have a “transition” for each “input” defined in the DFA
  so this means, that a transition must be defined for every input being considered in a dfa, for a state, so that one knows where to go from that state for each input.

• each “state” can have only ONE “transition” for each “input”
  well this rule is pretty self explanatory, so if you have already defined a transition for an input for a particular state, don’t create another transition for the same input from the same state.

Yeah these are the ones i remember. Hope it helps. Further these points can be used to differentiate a dfa from a nfa. Other simple rules for drawing would be :-

• make a start state, indicated with arrow pointing towards the state

• have at least one final state, indicated with concentric circles to draw the state boundary

• draw the transitions as arrows

• mark all the transitions with their respective input symbols