Theory of Computation Short Questions and Answers

41 All strings having equal number of a and b can be recognized by

A DFA

B NDFA

C PDA

D All of these

View Answer

Answer: PDA

42 The language L={ak bk|k>=1} is

A Type -3 Grammar

B Type -2 Grammar

C Type -1 Grammar

D Type -0 Grammar

View Answer

Answer: Type -2 Grammar

43 Which of the following problems are decidable?

1) Does a given program ever produce an output?

2) If L is context-free language, then, is ~L also context-free?

3) If L is regular language, then, is ~L also regular?

4) If L is recursive language, then, is ~L also recursive?

A 1,2,3,4

B 1,2

C 2,3,4

D 3,4

View Answer

Answer: Boyson Jensen

44 Following grammar

S-> bS

S -> b

S -> aA

A -> bA

A Type -3 grammar

B Type -2 grammar

C Type -1 grammar

D Type -0 grammar

View Answer

Answer: Type -3 grammar

45 6 Files F1,F2,F3,F4,F5 and F6 have 100,200,50,80,120,150 records repectively. In what order should they be sorted so as to optimize activity? Assume each file is accessed with the same frequency.

A F3,F4,F1,F5,F6,F2

B F2,F6,F5,F1,F4,F3

C F1,F2,F3,F4,F5,F6

D Ordering is immaterial as all files are accessed with the same frequency

View Answer

Answer: F3,F4,F1,F5,F6,F2

46 Consider the following statements :

I. Recursive languages are closed under complementation.

II. Recursively enumerable languages are closed under union.

III. Recursively enumerable languages are closed under complementation.

Which of the above statements are true ?

A I only

B I and II

C I and III

D I and III

View Answer

Answer: I and II

47 The language accepted by the nondeterministic pushdown automaton

A L(abb*a)

B {a} U L(abb*a)

C L(ab*a)

D {a} U L(ab*a)

View Answer

Answer: L(ab*a)

48 A FSM can be used to add how many given integers?

A 1

B 3

C 4

D 5

View Answer

Answer: 3

49 Which of the following is the most general phase structured grammar ?

A Regular

B Context-sensitive

C Context free

D None of the above

View Answer

Answer: Context-sensitive

50 Assume statements S1 and S2 defined as :

S1 : L2-L1 is recursive enumerable where L1 and L2 are recursive and recursive enumerable respectively.

S2 : The set of all Turing machines is countable.

Which of the following is true ?

A S1 is correct and S2 is not correct.

B Both S1 and S2 are correct.

C Both S1 and S2 are not correct.

D S1 is not correct and S2 is correct.

View Answer

Answer: Both S1 and S2 are not correct.

51 FSM can recognize

A Any grammar

B Only CFG

C Any unambiguous grammar

D Only regular grammar

View Answer

Answer: Only regular grammar

52 The regular expression for the following DFA

A ab*(b + aa*b)*

B a*b(b + aa*b)*

C a*b(b* + aa*b)

D a*b(b * + aa*b)*

View Answer

Answer: a*b(b * + aa*b)*

53 Given the following productions of a grammar :

A The language corresponding to the given grammar is a set of even number of a s.

B The language corresponding to the given grammar is a set of odd number of a s.

C The language corresponding to the given grammar is a set of even number of a’s followed by odd number of b s.

D The language corresponding to the given grammar is a set of odd number of a’s followed by even number of b s.

View Answer

Answer: The language corresponding to the given grammar is a set of odd number of a s.

54 Fred created a new automaton model which is a push down automaton but with two stacks and the added ability of having commands which do not read input tape but which can pop from one stack and push into the other.This new automaton can recognize (choose strongest result)

A Context free language

B Context sensitive language

C Regular language

D Languages recognizable by Turing machine

View Answer