1. BCA ( SEM. - 4th ) ,MAY -2008
OPERATING SYSTEM
SUBJECT CODE : BC-404
TIME-03 Hours Maximum Marks : 60
Instruction to candidates:
1) Section – A is Compulsory.
2) Attempt any Four questions from Section – B.
SECTION-A (10 X 2=20)
1. (a) What are the two main functions of an operating system?
(b) What is the principal advantage of multiprogramming ?
(c) Differentiate user level threads from kernel level threads.
(d) Which is the best condition to prevent from a deadlock?
(e) Define the concept of dynamic linking.
(f) What is compaction and why is it used?
(g) What is the difference between local page replacement and global page
replacement?
(h) How interrupt differ from trap?
(i) What is the purpose of system program?
(j) What is the function of dispatcher?
SECTION-B (4X10=40)
2. (a) What is operating system? Explain simple batch processing,
Multiprogramming, multitasking and distributed systems.
(b) Explain different types of scheduling queues and types of schedulers.
3. Consider the following set of processes, with the length of CPU – burst
time given in milliseconds:

2. Process Burst Time Priority
P1 10 3
P2 29 1
P3 3 3
P4 7 4
P5 12 2
The processes are assumed to have arrived in the order P1, P2,P3,P4 and P5 all at
time 0.
(a) What is turnaround time of each process for using FCFS, SJF, a non-
preemptive priority (a smaller priority number implies a higher priority) and
RR (quantum =10) scheduling.
(b) What is waiting time of each process for each of the scheduling algorithm in
part a?
4. (a) Explain Dining Philosopher problem in process synchronization.
(b) What are the four necessary conditions to occur a deadlock? Explain banker’s
algorithm.
5. (a) Why are page sizes always power of 2?
(b) Consider a logical address space of eight pages of 1024 words each ,
mapped onto a physical memory of 32 frames . How many bits are there in the
logical address and physical address?
6. (a) What is the causes of thrashing ? How it occurs and explain different
methods to prevent from thrashing .
(b) Explain the different operations performed on files .
7. Write short note on the following:
(a) Operating system security threats. (b) Data encryption and decryption.

3. BCA ( SEM. - 4th ) ,MAY -2009
OPERATING SYSTEM
SUBJECT CODE : BC-404
TIME-03 Hours Maximum Marks : 60
Instruction to candidates:
3. Section – A is Compulsory.
4. Attempt any Four questions from Section – B.
SECTION-A (10 X 2=20)
1. (a) What is difference between logical address and physical address?
(b) Give any one reason for the process to get blocked.
(c) What is Semaphore?
(d) What do you mean by simple batch processing system?
(e) Explain virtual memory and associative memory.
(f) List the three functions of resource management.
(g) What do you mean by program threats?
(h) What is indexed allocation?
(i) What do you mean by Resource allocation?
(j) Describe Critical Region?
SECTION-B (4X10=40)
2. Explain First come ,first served(FCFS) and Round Robin scheduling
algorithms.
3. State and Discuss the differences between Multiprogramming and
Multitasking.
4. What do you mean by page -faults? When do page-faults occur?
Describe the action taken by the O.S when page-fault occurs?
5. Explain the need and various services provided by Operating System.

4. 6. Write an algorithm to determine whether a given system is in a
deadlock and explain.
7. Write short notes on the following:
(a) Inter-process communication
(b) Real time system.