# Regular expressions MCQs [Theory of automata]

**Regular expressions MCQs in Theory of automata**

**Regular expressions are closed under**

(a) Union

(b) Intersection

(c) Kleen star

(d) none of these

(e) All of these

Answer:

(e) All of these

**Which strings are valid for Regular Expression aa(bb)***

a. bb, bbbb, bbbbbb,…

b. abb, abbbb, abbbbbb,…

c. aabb, aabbbb, aabbb,…

d. aabb, aabbbb, aabbbb,…

Answer:

aabb, aabbbb, aabbbb,…

**Regular Expression For All Strings Starts With a defined over {a,b}**

a. a(a+b)

b. a(a+b)*

c. a*

d. a*(a+b)*

Answer:

b. a(a+b)*

**Regular Expression For All Strings Starts With ab and ends with b defined over {a,b}**

a. ab(a+b)b

b. ab(a+b)* b

c. ab* b

d. None of these

Answer:

ab(a+b)* b

**Regular Expression For All Strings having always consecutive a’s defined over {a,b}**

a. (aa+b)

b. aa(b)*

c. (aa+b)*

d. None of these

Answer:

c. (aa+b)*

**Which one is correct regarding Regular Expression?**

a. We can draw FA for each regular expression

b. We can’t draw FA for some regular expression

c. RE defines regular languages

d. Both a and C

Answer:

d. Both a and C

**AUTOMATA THEORY MCQS**

**Regular expressions MCQs **

**FA DFA NFA MCQs **

## Examples of Regular Expression

- Regular Expression for no 0 or many triples of 0’s and many 1 in the strings.
- RegExp for strings of one or many 11 or no 11.
- A regular expression for ending with abb
- A regular expression for all strings having 010 or 101.
- Regular expression for Even Length Strings defined over {a,b}
- Regular Expression for strings having at least one double 0 or double 1.
- Regular Expression of starting with 0 and having multiple even 1’s or no 1.
- Regular Expression for an odd number of 0’s or an odd number of 1’s in the strings.
- Regular Expression for having strings of multiple double 1’s or null.
- Regular Expression (RE) for starting with 0 and ending with 1.
- RE for ending with b and having zero or multiple sets of aa and bb.
- A regular expression of the second last symbol is 1.
- RE for starting with 1 having zero or multiple even 1’s.
- Regular Expression for multiple a’s and multiple b’s.
- RE for exactly single 1 many 0’s |exactly single a many b.
- A regular expression for strings starting with aa and ending with ba.
- A regular expression for the language of all consecutive even length a’s.
- A regular expression for the language of all odd-length strings
- A regular expression for the language of all even length strings but ends with aa.
- A regular expression for the language of an odd number of 1s.
- A regular expression for the language of even length strings starting with a and ending with b in theory of automata.
- A regular expression for the language of all even length strings but starts with a.
- A Regular Expression for the Language of all strings with an even number of 0’s or even number of 1’s.
- A regular expression for the language of all those strings end with abb.
- A regular expression for string having must 010 or 101.
- Regular expression of strings begin with 110

Regular expression of strings begin and end with 110

Regular expression of strings containing exactly three consecutive 1’s. - A Regular Expression of all strings divisible by 4.
- A Regular Expression Strings that does not contain substring 110.