**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.Â bb, bbbb, bbbbbb,â€¦

b. abb, abbbb, abbbbbb,â€¦

c.Â aabb, aabbbb, aabbb,â€¦

d.Â aabb, aabbbb, aabbbb,â€¦

Answer:

aabb, aabbbb, aabbbb,â€¦

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

a.Â a(a+b)

c.Â a*

d.Â 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.Â ab(a+b)b

b. ab(a+b)* b

c.Â ab* b

d.Â None of these

Answer:

ab(a+b)* b

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

a.Â (aa+b)

b. Â aa(b)*

c.Â (aa+b)*

d.Â None of these

Answer:

c.Â (aa+b)*

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

a.Â We can draw FA for each regular expression

b. We canâ€™t draw FA for some regular expression

c.Â RE defines regular languages

d.Â Both a and C

Answer:

d.Â Both a and C

**AUTOMATA THEORY MCQS**

**Regular expressions MCQsÂ **

**FA DFA NFA MCQsÂ **

## Examples of Regular ExpressionÂ

- Regular Expression for no 0 or many triples of 0â€™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 1â€™s or no 1.
- Regular Expression for an odd number of 0â€™s or an odd number of 1’s in the strings.
- Regular Expression for having strings of multiple double 1â€™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 1â€™s.
- Regular Expression for multiple aâ€™s and multiple bâ€™s.
- RE for exactly single 1 many 0â€™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 0â€™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 Â strings begin with 110

Regular expression of Â strings begin and end with 110

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