In each of 20—28, (a) design an automaton with the given input alphabet that accepts the given set of strings, and (b) find a regular expression that defines the language accepted by the automaton.

21. Input alphabet = { 0 ,   1 } ; Accepts the set of all strings that start with 01.

(a)

To design an automaton with the given input alphabet that accepts the given set of strings.

Given information:

Input alphabet ={0,1} ; Accepts the set of all strings that start with 01

Calculation:

Given:

Input alphabet ={0,1}

Accepts all strings that start with 01

Let us design an automaton with 4 states s0,s1,s2 and s3 where s0 is the initial state and s3 is the accepting state. We draw each of the states as a circle with the name of the state within the circle. We draw an arrow towards the initial state and draw a second circle within the accepting states.

s0= Initial states1=Input is 0s2= Input starts with a 1 or 00s3= Input starts with 01

When we are at state s0 and the input is a 0, then we need to move to state s1

(b)

Find a regular expression that defines the language accepted by the automaton.