GATE-CS-2007

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Question 1

Consider the following statements about user level threads and kernel level threads. Which one of the following statement is FALSE?

Context switch time is longer for kernel level threads than for user level threads.
User level threads do not need any hardware support.
Related kernel level threads can be scheduled on different processors in a multi-processor system.
Blocking one kernel level thread blocks all related threads.

Question 2

Two processes, P1 and P2, need to access a critical section of code. Consider the following synchronization construct used by the processes:Here, wants1 and wants2 are shared variables, which are initialized to false. Which one of the following statements is TRUE about the above construct?v

  /* P1 */
while (true) {
  wants1 = true;
  while (wants2 == true);
  /* Critical
    Section */
  wants1=false;
}
/* Remainder section */       


/* P2 */
while (true) {
  wants2 = true;
  while (wants1==true);
  /* Critical
    Section */
  wants2 = false;
}
/* Remainder section */

It does not ensure mutual exclusion.
It does not ensure bounded waiting.
It requires that processes enter the critical section in strict alternation.
It does not prevent deadlocks, but ensures mutual exclusion.

Question 3

There are n stations in a slotted LAN. Each station attempts to transmit with a probability p in each time slot. What is the probability that ONLY one station transmits in a given time slot?

(1-p)^(n-1)
np(1-p)^(n-1)
p(1-p)^(n-1)
1-(1-p)^(n-1)

Question 4

In Ethernet when Manchester encoding is used, the bit rate is:

Half the baud rate.
Twice the baud rate.
Same as the baud rate.
None of the above

Question 5

In a token ring network the transmission speed is 10^7 bps and the propagation speed is 200 meters/micro second. The 1-bit delay in this network is equivalent to:

500 metres of cable.
200 metres of cable.
20 metres of cable.
50 metres of cable.

Question 6

The message 11001001 is to be transmitted using the CRC polynomial x³ + 1 to protect it from errors. The message that should be transmitted is:

11001001000
11001001011
11001010
110010010011

Question 7

The distance between two stations M and N is L kilometers. All frames are K bits long. The propagation delay per kilometer is t seconds. Let R bits/second be the channel capacity. Assuming that processing delay is negligible, the minimum number of bits for the sequence number field in a frame for maximum utilization, when the sliding window protocolis used, is:

GATECS200770

Question 8

Consider the following segment of C-code:

  int j, n;
  j = 1;
  while (j <= n)
        j = j*2;

The number of comparisons made in the execution of the loop for any n > 0 is: Base of Log is 2 in all options.

CEIL(logn) + 2
n
CEIL(logn)
FLOOR(logn) + 2

Question 9

Suppose the letters a, b, c, d, e, f have probabilities 1/2, 1/4, 1/8, 1/16, 1/32, 1/32 respectively. What is the average length of Huffman codes?

3
2.1875
2.25
1.9375

Question 10

Suppose the letters a, b, c, d, e, f have probabilities 1/2, 1/4, 1/8, 1/16, 1/32, 1/32 respectively. Which of the following is the Huffman code for the letter a, b, c, d, e, f?

0, 10, 110, 1110, 11110, 11111
11, 10, 011, 010, 001, 000
11, 10, 01, 001, 0001, 0000
110, 100, 010, 000, 001, 111

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