Gujarat University
MCA Semester III
Operating Systems
Date: Monday, 21st January, 2002 Maximum Marks: 50
Instructions:
1. Write answers of both section in separate answer books.
2. Figures to the right of each question indicate! Marks allocated to that question.
3 You may make assumptions wherever necessary. Indicate clearly such assumptions you have made.
SECTION - I
Q.1 (a) State whether the following statements are TRUE or FALSE. [6]
1. When arithmetic overflow occurs, current process is suspended until the error routine is serviced.
2. Pentium EFLAGS register is the example of Program Status Word.
3. In all modern operating systems, only processes can be scheduled, whereas threads can not be
Scheduled.
4. The wait and signal operations must be non-atomic.
5. Dekker’s algorithm functions, correctly only for two concurrent processes.
6. Starvation always results into deadlock.
7. Dynamic relocation means relocation of pages of the image while loading of the program. .
8. FCFS scheduling can be pre-emptive scheduling.
9. Average access time of disk is the sum of average seeks time and latency.
10. RAID level-l provides high level of data redundancy through mirroring.
11. UNIX I-node structure provides three levels of indirect blocks to create a file of size in excess of 4
GB.
12. In public key encryption, either public key or private key can be used for encryption of the message by
the sender.
(b) Define the following terms (ANY THREE) [3]
(i) Throughput (ii) Cache Coherence (iii)Test & Set (iv) Trap (v) Thrashing
Q. 2 (a) Which could be the possible reasons for process creation? Explain at least 10 different reasons for
process termination. [4]
(b) Draw the standard five-state transition diagram and explain how the processes change the states. Does
the UNIX operating system also have the same number of process states? [4]
OR
Q.2 What is microkernel? Explain diagrammatically how microkernel differs from layered kernel. Describe
the distinct benefits of microkernel organization. [8]
Q.3 Describe the Flynn's classification of parallel processor architectures in detail. Also discuss the
characteristics of Symmetric Multi Processing and Fault Tolerant systems briefly. [8]
OR
Q.3 Write and explain the following classical algorithms: [8]
1. Dekker’s algorithm for mutual exclusion
2. Producer/Consumer problem with circular buffer
SECTION II
Q.4 Write short notes on ANY THREE of the following: [9]
(1) RAID
(2) Process Migration
(3) Unix Process states and Process Transition diagram
(4) POSIX Threads
(5) Bakery algorithm for mutual exclusion
(6) Disk Scheduling policies
Q.5 Consider the following snapshot of a system. There are no current outstanding queued unsatisfied and
p indicates process). [8]
Currently available
rl r2 r3 a4
2 1 0 0
Current allocation Maximum demand Still needs
process r1 r2 r3 r4 r1 r2 r3 r4 r1 r2 r3 r4
p1 0 0 1 2 0 0 1 2
p2 2 0 0 0 2 7 5 0
p3 0 0 3 4 6 6 5 6
p4 2 3 5 4 4 3 5 6
p5
(a) Compute what each process still might request and display in the colunms labeled "still needs”.
(b) Applying Banker’s algorithm whether this system currently in a safe or unsafe state? Why?
(c) What is the possible order in which processes can finish without any deadlock?
OR
Q.5 Describe with the help of diagrams the primitive contiguous memory allocation methods
(i) static (fixed) partitioning (ii) dynamic partitioning and first-fit, best-fit and next-fit algorithms being
applied for placement of incoming processes. Mention the resultant pros and cons of these allocation methods and placement algorithms. [8]
Q. 6 (a) What is the difference between paging and virtual memory management systems? What is the role of
Translation Lookaside Buffer (TIB) in virtual memory management? [4]
(b) Explain in detail various page replacement policies that can be applied to virtual memory management
systems. [4]
OR
Q.6 What is the basic criteria for scheduling of processes in a uniprocessor environment? Describe
FCFS, RR, SPN,SRT, HRRN, Feedback and Fair-share scheduling methods briefly. Given the
following data, calculate Turn around Time for each process and average Turn around for all processes using FCFS, SPN and SRT algorithms. [8]
Process A B C D E
Arrival time 0 1 3 9 12
Service time 3 5 2 5 5
