Code: AC13 Subject:
OPERATING SYSTEMS
Time: 3 Hours Max. Marks: 100
NOTE: There are 9 Questions in all.
· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.
· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.
· Any required data not explicitly given, may be suitably assumed and stated.
Q.1 Choose the correct or best alternative in the following: (2x10)
a. Banker’s algorithm for resource allocation deals with
(A) Deadlock prevention. (B) Deadlock avoidance.
(C) Deadlock recovery. (D) Mutual exclusion.
b. Moving process from main memory to disk is called
(A) Scheduling. (B) Caching.
(C) Swapping. (D) Spooling.
c. What is name of operating system that read and reacts in terms of actual time?
(A) Real time system (B) Batch system
(C) Quick response system (D) Time sharing system
d. In which of the following page replacement policies, Bolady’s anomaly occurs?
(A) FIFO (B) LRU
(C) LFU (D) SRU
e. Producer consumer problem can be solved using
(A) Semaphores. (B) Event counters.
(C) Monitors. (D) All of the above.
f. The principle of ‘locality of reference’ justify the use of
(A) DMA. (B) Polling.
(C) Cache memory. (D) Virtual memory.
g. Virtual memory is
(A) an extreme large main memory.
(B) an extremely large secondary memory.
(C) an illusion of an extremely large memory.
(D) a type of memory used in computers.
h. In Round Robin CPU scheduling, as the time quantum is increased, the average turn around time
(A) Varies irregular. (B) Remains constant.
(C) Increases. (D) Decreases.
i. In which of the following strategies a program is located in the smallest available hole in the main memory.
(A) Buddy (B) Best-fit
(C) First-fit (D) Worst-fit
j. To avoid the race condition the number of processes that may be simultaneously inside the critical section is
(A) 0 (B) 1
(C) 2 (D) 3
Answer any FIVE Questions out of EIGHT Questions.
Each question carries 16 marks.
Q.2 a. What is the purpose of system calls? List the system calls used in operating system. (8)
b. Describe the following problems of synchronization: (8)
(i) Reader-Writer problem.
(ii) Dining Philosophers problem.
Q.3 a. Explain the advantages of threads over processes. (8)
b. Draw Gantt chart for the CPU schedule under FCFS and SJF algorithms for the following ready queue:
Queue head : Head
Tail
Process: P1 P2 P3 P4
Burst time: 6 8 7 3
Also compute average turnaround time and average waiting time. (8)
Q.4 a. What is Remote Procedure Calls (RPC)? Explain the execution of RPC. (8)
b. Consider a system with 5 processes {P0.....P4} and three resource type R1, R2, R3
Type R1 has 10 instances
Type R2 has 5 instances
Type R3 has 7 instances
Suppose that at time T0 the following snapshot of the system has been taken
|
|
Allocation |
Max |
Available |
||||||
|
|
R1 |
R2 |
R3 |
R1 |
R2 |
R3 |
R1 |
R2 |
R3 |
|
P0 |
0 |
1 |
0 |
7 |
5 |
3 |
3 |
3 |
2 |
|
P1 |
2 |
0 |
0 |
3 |
2 |
2 |
|
|
|
|
P2 |
3 |
0 |
2 |
9 |
0 |
2 |
|
|
|
|
P3 |
2 |
1 |
1 |
2 |
2 |
2 |
|
|
|
|
P4 |
0 |
0 |
2 |
4 |
3 |
3 |
|
|
|
Answer the following using Banker’s algorithm
(i) What is the content of Need matrix?
(ii) Is the system in safe state?
(iii) If a request from P1 arrives for (1, 0, 2) can the request be granted immediately? What is next state if request is granted? (8)
Q.5 a. Consider the following page reference string
7,0,1,2,0,3,0,4,2,3,0,3,2,1,2,0,1,7,0,1
How many page fault would occur for the following page replacement algorithms for 3 page frame? All frames are initially empty.
(i) FIFO replacement (ii) Optimal replacement. (8)
b. Explain the following memory allocation methods with suitable example.
(i) Linked Allocation. (ii) Indexed Allocation. (8)
Q.6 a. Explain the steps of life cycle of I/O request. (8)
b. Suppose the head of a moving head disk with 200 tracks numbered 0 to 199 is initially at 53. Prepare a SCAN and SSTF disk schedule for the following sequence 98, 183, 37, 122, 14, 124, 65, 67. Show the movement of the head pictorially. (8)
Q.7 a. Contrast the various network topologies in terms of reliability. (8)
b. Describes the following Election algorithm:
(i) Bully Algorithm.
(ii) Ring Algorithm. (8)
Q.8 a. Explain the following Program Threats
(i) Trojan Horse
(ii) Trap Door (8)
b. Explain the layered architecture of Windows 2000 with block diagram. (8)
Q.9 Write short note on the following:
(i) Real Time Systems.
(ii) Memory Paging.
(iii) Mutual Exclusion in Distributed Operating System.
(iv) Intrusion Detection. (4 x 4 = 16)