This set of Automata Theory Multiple Choice Questions & Answers (MCQs) focuses on “Chomsky Normal Form”.

1. The format: A->aB refers to which of the following?

a) Chomsky Normal Form

b) Greibach Normal Form

c) Backus Naur Form

d) None of the mentioned

View Answer

Explanation: A context free grammar is in Greibach Normal Form if the right hand sides of all the production rules start with a terminal, optionally followed by some variables.

2. Which of the following does not have left recursions?

a) Chomsky Normal Form

b) Greibach Normal Form

c) Backus Naur Form

d) All of the mentioned

View Answer

Explanation: The normal form is of the format:

A->aB where the right hand side production tends to begin with a terminal symbo, thus having no left recursions.

3. Every grammar in Chomsky Normal Form is:

a) regular

b) context sensitive

c) context free

d) all of the mentioned

View Answer

Explanation: Conversely, every context frr grammar can be converted into Chomsky Normal form and to other forms.

4. Which of the production rule can be accepted by Chomsky grammar?

a) A->BC

b) A->a

c) S->e

d) All of the mentioned

View Answer

Explanation: in CNF, the production rules are of the form:

A->BC

A-> a

S->e

5. Given grammar G:

(1)S->AS

(2)S->AAS

(3)A->SA

(4)A->aa

Which of the following productions denies the format of Chomsky Normal Form?

a) 2,4

b) 1,3

c) 1, 2, 3, 4

d) 2, 3, 4

View Answer

Explanation: The correct format: A->BC, A->a, X->e.

6. Which of the following grammars are in Chomsky Normal Form:

a) S->AB|BC|CD, A->0, B->1, C->2, D->3

b) S->AB, S->BCA|0|1|2|3

c) S->ABa, A->aab, B->Ac

d) All of the mentioned

View Answer

Explanation: We can eliminate the options on the basis of the format we are aware of: A->BC, B->b and so on.

7. With reference to the process of conversion of a context free grammar to CNF, the number of variables to be introduced for the terminals are:

S->ABa

A->aab

B->Ac

a) 3

b) 4

c) 2

d) 5

View Answer

Explanation: According to the number of terminals present in the grammar, we need the corresponding that number of terminal variables while conversion.

8. In which of the following, does the CNF conversion find its use?

a) CYK Algorithm

b) Bottom up parsing

c) Preprocessing step in some algorithms

d) All of the mentioned

View Answer

Explanation: Besides the theoretical significance of CNF, it conversion scheme is helpful in algorithms as a preprocessing step, CYK algorithms and the bottom up parsing of context free grammars.

9. Let G be a grammar. When the production in G satisfy certain restrictions, then G is said to be in ___________.

a) restricted form

b) parsed form

c) normal form

d) all of the mentioned

View Answer

Explanation: When the production in G satisfy certain restrictions, then G is said to be in ‘normal form’.

10. Let G be a grammar: S->AB|e, A->a, B->b

Is the given grammar in CNF?

a) Yes

b) No

View Answer

Explanation: e is allowed in CNF only if the starting variable does not occur on the right hand side of the derivation.

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