21.
Given the following statements :

(A) A class
of languages that is closed under union and complementation has to be closed
under intersection.

(B) A class
of languages that is closed under union and intersection has to be closed under
complementation.

Which of the
following options is correct?

(1) Both (A)
and (B) are false.

(2) Both (A)
and (B) are true.

(3) (A) is
true, (B) is false.

(4) (A) is
false, (B) is true.

Answer: 3

22. Let
G = (V,T,S,P) be a context-free grammar such that every one of its productions
is of the form A→v, with |v| = K>1. The derivation tree for any W Ïµ L(G) has
a height h such that

23. Given
the following two languages:

L1 = {a

^{n}b^{n}|n≥0, n≠100}
L2 = {w Ïµ {a,b,c}*|
n

_{a}(w) = n_{b}(w) = n_{c}(w)}
Which of the
following options is correct?

(1) Both L1
and L2 are not context free language.

(2) Both L1
and L2 are context free language.

(3) L1 is
context free language, L2 is not context free language.

(4) L1 is
not context free language, L2 is context free language.

Answer: 3

24. A
recursive function h, is defined as follows:

h(m)=k, if m=0

= 1, if m=1

=
2h(m-1) + 4h(m-2), if m≥2

If the value
of h(4) is 88 then the value of k is:

(1) 0

(2) 1

(3) 2

(4) -1

Answer: 3

25. Suppose
there are n stations in a slotted LAN. Each station attempts to transmit with a
probability P in each time slot. The probability that only one station
transmits in a given slot is ..................

(1) nP(1-P)

^{n-1}
(2) nP

(3) P(1-P)

^{n-1}
(4) n

^{P}(1-P)^{n-1}
Answer: 1

26. Station
A uses 32 byte packets to transmit messages to station B using sliding window
protocol. The round trip delay between A and B is 40 milli seconds and the
bottleneck bandwidth on the path between A and B is 64 kbps. The optimal window
size of A is

(1) 20

(2) 10

(3) 30

(4) 40

Answer: 2

27. Let
G(x) be generator polynomial used for CRC checking. The condition that should
be satisfied by G(x) to correct odd numbered error bits, will be:

(1) (1+x) is
factor of G(x)

(2) (1-x) is
factor of G(x)

(3) (1+x

^{2}) is factor of G(x)
(4) x is
factor of G(x)

Answer: 1

28. In
a packet switching network, if the message size is 48 bytes and each packet
contains a header of 3 bytes. If 24 packets are required to transmit the
message, the packet size is ................

(1) 2 bytes

(2) 1 byte

(3) 4 bytes

(4) 5 bytes

Answer: 4

29. In
RSA public key cryptosystem suppose n=p*q where p and q are primes. (e,n) and
(d,n) are public and private keys respectively. Let M be an integer such that
0<M<n and É¸(n)=(p-1)(q-1).

Which of the
following equations represent RSA public key cryptosystem?

I. C≡M

^{e}(mod n), M≡(C)^{d}(mod n)
II. ed≡1(mod
n)

III. ed≡(mod
É¸(n))

IV. C≡M

^{e}(mod É¸n), M≡C^{d}(mod É¸n)**Codes:**

(1) I and II

(2) I and III

(3) II and
III

(4) I and IV

Answer: 2

30. A
node X on a 10 Mbps network is regulated by a token bucket. The token bucket is
filled at a rate of 2 Mbps. Token bucket is initially filled with 16 megabits.
The maximum

duration
taken by X to transmit at full rate of 10 Mbps is ............ secs.

(1) 1

(2) 2

(3) 3

(4) 4

Answer: 2

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