GATE CS 2010

Question 21

Consider the methods used by processes P1 and P2 for accessing their critical sections whenever needed, as given below. The initial values of shared boolean variables S1 and S2 are randomly assigned.

Method Used by P1
while (S1 == S2) ;
Critica1 Section
S1 = S2;

Method Used by P2
while (S1 != S2) ;
Critica1 Section
S2 = not (S1);

Which one of the following statements describes the properties achieved?

• Mutual exclusion but not progress
• Progress but not mutual exclusion
• Neither mutual exclusion nor progress
• Both mutual exclusion and progress

Question 22

A system uses FIFO policy for page replacement. It has 4 page frames with no pages loaded to begin with. The system first accesses 100 distinct pages in some order and then accesses the same 100 pages but now in the reverse order. How many page faults will occur?

• 196
• 192
• 197
• 195

Question 23

Which of the following statements are true?

I. Shortest remaining time first scheduling may cause starvation
II. Preemptive scheduling may cause starvation
III. Round robin is better than FCFS in terms of response time

• I only
• I and III only
• II and III only
• I, II and III

Question 24

Consider a company that assembles computers. The probability of a faulty assembly of any computer is p. The company therefore subjects each computer to a testing process.This testing process gives the correct result for any computer with a probability of q. What is the probability of a computer being declared faulty?

• pq + (1 - p)(1 - q)
• (1 - q) p
• (1 - p) q
• pq

Question 25

What is the probability that divisor of 10⁹⁹ is a multiple of 10⁹⁶?

• 1/625
• 4/625
• 12/625
• 16/625

Question 26

The degree sequence of a simple graph is the sequence of the degrees of the nodes in the graph in decreasing order. Which of the following sequences can not be the degree sequence of any graph?  

(I) 7, 6, 5, 4, 4, 3, 2, 1
(II) 6, 6, 6, 6, 3, 3, 2, 2
(III) 7, 6, 6, 4, 4, 3, 2, 2
(IV) 8, 7, 7, 6, 4, 2, 1, 1 

• I and II
  

• III and IV
  

• IV only
  

• II and IV
  

Question 27

Suppose the predicate F(x, y, t) is used to represent the statement that person x can fool person y at time t. which one of the statements below expresses best the meaning of the formula ∀x∃y∃t(¬F(x, y, t))?

• Everyone can fool some person at some time
• No one can fool everyone all the time
• Everyone cannot fool some person all the time
• No one can fool some person at some time

Question 28

What is the Boolean expression for the output f of the combinational logic circuit of NOR gates given below?

• (Q+R)\'
• (P+Q)\'
• (P+R)
• (P+Q+R)\'

Question 29

In the sequential circuit shown below,if the initial value of the output Q1Q0 is 00,what are the next four values of Q1Q0? 

[caption width="800"] [/caption]

• 11, 10, 01, 00

• 10, 11, 01, 00

• 10, 00, 01, 11

• 11, 10, 00, 01

Question 30

A 5-stage pipelined processor has Instruction Fetch(IF),Instruction Decode(ID),Operand Fetch(OF),Perform Operation(PO)and Write Operand(WO)stages.The IF,ID,OF and WO stages take 1 clock cycle each for any instruction.The PO stage takes 1 clock cycle for ADD and SUB instructions,3 clock cycles for MUL instruction,and 6 clock cycles for DIV instruction respectively.Operand forwarding is used in the pipeline.What is the number of clock cycles needed to execute the following sequence of instructions?

     Instruction           Meaning of instruction
  I0 :MUL R2 ,R0 ,R1	      R2 ¬ R0 *R1
  I1 :DIV R5 ,R3 ,R4  	      R5 ¬ R3/R4
  I2 :ADD R2 ,R5 ,R2	      R2 ¬ R5+R2
  I3 :SUB R5 ,R2 ,R6	      R5 ¬ R2-R6

• 13
• 15
• 17
• 19