# UGC NET Computer Science Questions Paper II December 2008 - Part 2

11.       If a code is ‘t’ error detecting, the minimum hamming distance should be equal to:
(A) t-1
(B) t
(C) t+1
(D) 2t+1
Explanation:
For error detection, formula is t+1
For error correction, formula is 2t+1
12.       A relation R in {1,2,3,4,5,6} is given by {(1,2),(2,3),(3,4),(4,4),(4,5)}. This relation is:
(A) reflexive
(B) symmetric
(C) transitive
(D) not reflexive, not symmetric and not transitive
13.       The dual of the switching function x+yz is:
(A) x+yz
(B) x’+y’z’
(C) x(y+z)
(D) x’(y’+z’)
14.       The characteristic equation of D flip-flop is:
(A) Q=1
(B) Q=0
(C) Q=D’
(D) Q=D
15.       If 4 input multiplexers drive a 4 input multiplexer, we get a:
(A) 16 input MUX
(B) 8 input MUX
(C) 4 input MUX
(D) 2 input MUX

16.       The throughput of slotted ALOHA is given by:
(A) S=G
(B) S=GeG
(C) S=Ge-G
(D) S=eG
17.       Congestion control is done by:
(A) Network layer
(B) Physical layer
(C) Presentation layer
(D) Application layer
Explanation:
Routing and forwarding are functions of this layer, as well as addressing, internetworking, error handling, congestion control and packet sequencing.
18.       Assertion (A): Twisted pairs are widely used as transmission medium.
Reasoning (R): Twisted pairs have adequate performance and low cost.
(A) Both (A) and (R) are true and (R) is the correct explanation for (A)
(B) Both (A) and (R) are true but (R) is not the correct explanation
(C) (A) is true but (R) is false
(D) (A) is false but (R) is true
19.       An example of a non-adaptive routing algorithm is:
(A) Shortest path routing
(B) Centralised routing
(C) Baran’s hot potato routing
(D) Baran’s backward learning algorithm
Explanation:
Non-Adaptive Routing Algorithm: These algorithms do not base their routing decisions on measurements and estimates of the current traffic and topology. Instead the route to be taken in going from one node to the other is computed in advance, off-line, and downloaded to the routers when the network is booted. This is also known as static routing.
Eg: Shortest path routing:- To send a packet from one node to another find the shortest path between the pair of nodes.
Adaptive Routing Algorithm: These algorithms change their routing decisions to reflect changes in the topology and in traffic as well. These get their routing information from adjacent routers or from all routers. The optimization parameters are the distance, number of hops and estimated transit time.
20.    IP address in B class is given by:
(A) 125.123.123.2
(B) 191.023.21.54
(C) 192.128.32.56
(D) 10.14.12.34