Mumbai University > Informatica Technology > Sem 4 > Automata Theory

Marks: 05

Year:DEC 16

The theory of computation is a branch of computer science that deals with how problems are solved using algorithms.

It has three branches, namely; the computational complexity theory, the computability theory, and the automaton theory.

The automaton or automata theory is the study of abstract mathematical machines or systems that can be used to solve computational problems.

An automaton is made up of states and transitions, and as it sees a symbol or letter of input, it makes a transition to another state taking the current state and symbol as input.

The automaton or automata theory has several classes that include the Deterministic Finite Automata (DFA) and the Nondeterministic Finite Automata (NFA).

These two classes are transition functions of automata or automaton.

In transition, DFA cannot use n empty string, and it can be understood as one machine. If the string ends at a state that is not an acceptable state, DFA will reject it.

A DFA machine can be constructed with every input and output.

DFA only has one state transition for every symbol of the alphabet, and there is only one final state for its transition which means that for each character that is read, there is one corresponding state in DFA.

It is easier to check membership in DFA but it is more difficult to construct. Backtracking is allowed in DFA, and it requires more space than NFA.

Backtracking is not always allowed in NFA.

While it is possible in some cases, in others it is not. It is easier to construct NFA, and it also requires less space, but it is not possible to construct an NFA machine for every input and output.

It is understood as several tiny machines that compute simultaneously, and membership can be harder to check.

It uses Empty String Transition, and there are numerous possible next states for each pair of state and input symbol.

It starts at a specific state and reads the symbols, and the automaton then determines the next state which depends on the current input and other consequent events. At its accepting state, NFA accepts the string and rejects it otherwise.