Code: C-13 Subject: OPERATING SYSTEMS
Time: 3 Hours 
Max.
Marks: 100
NOTE: There are 9 Questions in all.
· Question 1 is compulsory and carries 20 marks.
· 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 Define the following: (2x10)
a. Deadlock.
b. Circular Wait.
c. Interrupt handler.
d. Loader.
e. Locality.
f. Reference bit.
g. Starvation.
h. System Software.
i. Swapping.
j. Gantt Chart.
Answer any FIVE Questions out of EIGHT Questions.
Each question carries 16 marks.
Q.2 a. Suppose
a paging system has 
virtual addresses and uses 
locations in
primary memory for integers g, h and k. What is the page size of the system
that is implied by the virtual and physical address sizes? How many bits are
required to store a virtual address? (4)
b. Suppose the page size in a computing environment is 1 KB. What is the page number and the offset for the following:
(i) 899 (a decimal number)
(ii) 23456 (a decimal number)
(iii) 0x3F244 (a hexadecimal number)
(iv) 0x0017C (a hexadecimal number) (4)
c. Define critical section. What are the requirements of a mechanism to control access to critical section? (8)
Q.3 a. What do you understand by a malicious program? Explain Trap Door, Trojan horse, virus and worm. (9)
b. Which types of malicious programs replicate? (2)
c. For each of the following transitions between process states, indicate whether the transition is possible. If it is possible, give an example.
(i)
Run 
ready.
(ii)
Run blocked.
(iii)
Run swapped-blocked.
(iv)
Blocked run.
(v)
Run terminated. (5)
Q.4 a. Describe various page replacement algorithms along with their merits and demerits. (10)
b. Suppose the page size in a computing environment is 2 KB and the size of physical memory is 100 MB. How many entries would an associative memory need in order to implement a page table for the memory? (6)
Q.5 a. What is a PCB? Describe the contents of PCB. (6)
b. In paging (assuming the page size is a power of 2), why is it not necessary to add the page offset to the starting address of the page frame to generate a physical address? (5)
c. How does a system recover in case of a deadlock? (5)
Q.6 a. Describe various scheme for allocating secondary storage to files. (10)
b. A system uses
resources of two different types (
and 
) and has four processes 
. Is the state
of the system shown below safe? Justify your answer. If the system is safe,
show how all the processes could complete their execution successfully. If the
system is unsafe, show how deadlock might occur.
(6)
|
Process |
Current Allocation |
Maximum Allocation |
Resources Available |
|||
|
|
|
|
|
|
|
|
|
|
1 |
2 |
4 |
2 |
|
|
|
|
0 |
1 |
1 |
2 |
1 |
1 |
|
|
1 |
0 |
1 |
3 |
|
|
|
|
2 |
0 |
3 |
2 |
|
|
Q.7 a. On a disk with 1000 cylinders numbered 0 to 999, compute the number of tracks the disk arm must move to satisfy all the requests in the disk queue. Assume the last request serviced was at track 756 and the head is moving toward track 0. The queue in FIFO order contains requests for the following tracks: 811, 348, 153, 968, 407, 500. Perform the computation for the following scheduling algorithms
FCFS, SSTF, SCAN, LOOK, C-SCAN, C-LOOK. (12)
b. Define the following with respect to tertiary-storage performance.
(i) access latency.
(ii) Effective bandwidth. (4)
Q.8 a. Explain the following with respect to Linux system.
(i) Process scheduling.
(ii) The Virtual file system. (6)
b. Describe any four network topologies along with its advantages and disadvantages. (10)
Q.9 Write short note on the following:
(i) Distributed operating system.
(ii) Threads.
(iii) Semaphores.
(iv) Data Encryption. (4 x 4 = 16)