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?

A
Context switch time is longer for kernel level threads than for user level threads.
B
User level threads do not need any hardware support.
C
Related kernel level threads can be scheduled on different processors in a multi-processor system.
D
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 */

A
It does not ensure mutual exclusion.
B
It does not ensure bounded waiting.
C
It requires that processes enter the critical section in strict alternation.
D
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?

A
(1-p)^(n-1)
B
np(1-p)^(n-1)
C
p(1-p)^(n-1)
D
1-(1-p)^(n-1)

Question 4

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

A
Half the baud rate.
B
Twice the baud rate.
C
Same as the baud rate.
D
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:

A
500 metres of cable.
B
200 metres of cable.
C
20 metres of cable.
D
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:

A
11001001000
B
11001001011
C
11001010
D
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.

A
CEIL(logn) + 2
B
n
C
CEIL(logn)
D
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?

A
3
B
2.1875
C
2.25
D
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?

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

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