Gate IT 2007

Question 51

In a multi-user operating system on an average, 20 requests are made to use a particular resource per hour. The arrival of requests follows a Poisson distribution. The probability that either one, three or five requests are made in 45 minutes is given by :

• 6.9 × 10⁶ × e^-20

• 1.02 × 10⁶ × e^-20

• 6.9 × 10³ × e^-20

• 1.02 × 10³ × e^-20

Question 52

A demand paging system takes 100 time units to service a page fault and 300 time units to replace a dirty page. Memory access time is 1 time unit. The probability of a page fault is p. In case of a page fault, the probability of page being dirty is also p. It is observed that the average access time is 3 time units. Then the value of p is

• 0.194
• 0.233
• 0.514
• 0.981

Question 53

The contents of the text file t1 txt containing four lines are as follows :
a1 b1
a2 b2
a3 b2
a4 b1
The contents of the text file t2 txt containing five lines are as follows :
a1 c1
a2 c2
a3 c3
a4 c3
a5 c4
Consider the following Bourne shell script :

C

 awk - F \'  \'  \' {Print $1, $2} \' t1.txt |
while read a b ; do
            awk -v aV = $ a - v by = $b  - F \' \'
            aV = = $1 (print aV, bV, $2 ) \' t2.txt
done

Which one of the following strings will NOT be present in the output generated when the above script in run?
(Note that the given strings may be substrings of a printed line.)

• "b1 c1"
• "b2 c3"
• "b1 c2"
• "b1 c3"

Question 54

For the network given in the figure below, the routing tables of the four nodes A, E, D and G are shown. Suppose that F has estimated its delay to its neighbors, A, E, D and G as 8, 10, 12 and 6 msecs respectively and updates its routing table using distance vector routing technique.


A.

B.

C.

D.

• A
• B
• C
• D

Question 55

In the waveform (a) given below, a bit stream is encoded by Manchester encoding scheme. The same bit stream is encoded in a different coding scheme in wave form (b). The bit stream and the coding scheme are

• 1000010111 and Differential Manchester respectively
• 0111101000 and Differential Manchester respectively
• 1000010111 and Integral Manchester respectively
• 0111101000 and Integral Manchester respectively

Question 56

Let us consider a statistical time division multiplexing of packets. The number of sources is 10. In a time unit, a source transmits a packet of 1000 bits. The number of sources sending data for the first 20 time units is 6, 9, 3, 7, 2, 2, 2, 3, 4, 6, 1, 10, 7, 5, 8, 3, 6, 2, 9, 5 respectively. The output capacity of multiplexer is 5000 bits per time unit. Then the average number of backlogged of packets per time unit during the given period is

• 5
• 4.45
• 3.45
• 0

Question 57

Let us consider a statistical time division multiplexing of packets. The number of sources is 10. In a time unit, a source transmits a packet of 1000 bits. The number of sources sending data for the first 20 time units is 6, 9, 3, 7, 2, 2, 2, 3, 4, 6, 1, 10, 7, 5, 8, 3, 6, 2, 9, 5 respectively. The output capacity of multiplexer is 5000 bits per time unit. Then the average number of backlogged of packets per time unit during the given period is

• 3
• 4.26
• 4.53
• 5.26

Question 58

A broadcast channel has 10 nodes and total capacity of 10 Mbps. It uses polling for medium access. Once a node finishes transmission, there is a polling delay of 80 μs to poll the next node. Whenever a node is polled, it is allowed to transmit a maximum of 1000 bytes. The maximum throughput of the broadcast channel is

• 1 Mbps
• 100/11 Mbps
• 10 Mbps
• 100 Mbps

Question 59

Consider a selection of the form σA≤100(r), where r is a relation with 1000 tuples. Assume that the attribute values for A among the tuples are uniformly distributed in the interval [0, 500]. Which one of the following options is the best estimate of the number of tuples returned by the given selection query ?

• 50
• 100
• 150
• 200

Question 60

Consider the following two transactions : T₁ and T₂. Which of the following schemes, using shared and exclusive locks, satisfy the requirements for strict two phase locking for the above transactions?

• A
• B
• C
• D