Automata Theory Questions and Answers – Regular Language & Expression – 1

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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

Answer: d
Explanation: None.
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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

Answer: d
Explanation: All are equivalent to union operation.

3. Precedence of regular expression in decreasing order is
a) * , . , +
b) . , * , +
c) . , + , *
d) + , a , *
View Answer

Answer: a
Explanation: None.
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4. Regular expression Φ* is equivalent to
a) ϵ
b) Φ
c) 0
d) 1
View Answer

Answer: a
Explanation: None.

5. a? is equivalent to
a) a
b) a+Φ
c) a+ϵ
d) wrong expression
View Answer

Answer: c
Explanation: Zero or one time repetition of previous character .
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6. ϵL is equivalent to
a) ϵ
b) Φ
c) L
d) Φϵ
View Answer

Answer: c
Explanation: None.

7. (a+b)* is equivalent to
a) b*a*
b) (a*b*)*
c) a*b*
d) none of the mentioned
View Answer

Answer: b
Explanation: None.
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8. ΦL is equivalent to
a) LΦ & Φ
b) Φ & L
c) L & L
d) ϵ & L
View Answer

Answer: a
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

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

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

Sanfoundry Global Education & Learning Series – Automata Theory.
To practice all areas of Automata Theory, here is complete set of 1000+ Multiple Choice Questions and Answers.

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1 thought on “Automata Theory Questions and Answers – Regular Language & Expression – 1”

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

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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