CFG

Question 1
   
A
5
B
4
C
3
D
2
       Theory-of-Computation       CFG       Gate 2005-IT
Question 1 Explanation: 
Total 5 parse trees possible (solved in previous question).
Question 2
Which of the following features cannot be captured by context-free grammars?
A
Syntax of if-then-else statements
B
Syntax of recursive procedures
C
Whether a variable has been declared before its use
D
Variable names of arbitrary length
       Theory-of-Computation       CFG       Gate-1994
Question 2 Explanation: 
Context free grammars are used to represent syntactic rules while designing a compiler.
Syntactic rules not checking the meaningful things such as if a variable is declared before it use (or) not.
Like this, things are handled by semantic analysis phase.
Question 3
If G is a context-free grammar and w is a string of length l in L(G), how long is a derivation of w in G, if G is Chomsky normal form?
A
2l
B
2l + 1
C
2l - 1
D
l
       Theory-of-Computation       CFG       Gate-1992
Question 3 Explanation: 
For CNF, it is
2l - 1
For GNF, it is
l
There are 3 questions to complete.