This set of Automata Theory Multiple Choice Questions & Answers (MCQs) focuses on “Regular Language & Expression”.

1. A regular language over an alphabet a is one that can be obtained from

a) union

b) concatenation

c) kleene

d) All of the mentioned

View Answer

Explanation : None.

2. Regular expression {0,1} is equivalent to

a) 0 U 1

b) 0 / 1

c) 0 + 1

d) All of the mentioned

View Answer

Explanation : All are equivalent to union operation.

3. Precedence of regular expression in decreasing order is

a) * , . , +

b) . , * , +

c) . , + , *

d) + , a , *

View Answer

Explanation : None.

4. Regular expression Φ* is equivalent to

a) ϵ

b) Φ

c) 0

d) 1

View Answer

Explanation : None.

5. a? is equivalent to

a) a

b) a+Φ

c) a+ϵ

d) wrong expression

View Answer

Explanation : Zero or one time repetition of previous character .

6. ϵL is equivalent to

a) ϵ

b) Φ

c) L

d) Lϵ

View Answer

Explanation : None.

7. (a+b)* is equivalent to

a) b*a*

b) (a*b*)*

c) a*b*

d) none of the mentioned

View Answer

Explanation : None.

8. ΦL is equivalent to

a) LΦ

b) Φ

c) L

d) ϵ

View Answer

Explanation : None.

9. Which of the following pair of regular expression are not equivalent?

a) 1(01)* and (10)*1

b) x(xx)* and (xx)*x

c) (ab)* and a*b*

d) x+ and x*x+

View Answer

Explanation : (ab)*=(a*b*)*.

10. Consider following regular expression

i) (a/b)* ii) (a*/b*)* iii) ((ϵ/a)b*)*

Which of the following statements is correct

a) i,ii are equal and ii,iii are not

b) i,ii are equal and i,iii are not

c) ii,iii are equal and i,ii are not

d) all are equal

View Answer

Explanation : All are equivalent to (a+b)*.

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In Q9 I think the explanation is wrong. Shouldn’t it be (a+b)*=(a*b*)*?

Please verify. Thanks