(AUTONOMOUS)
B. Tech VII Semester Supplementary Examinations, May 2018
(Regulations: VCE-R11/R11A)
OPERATING SYSTEMS
(Electronics and Communication Engineering)
Date: 24 May, 2018 AN Time: 3 hours Max Marks: 75
Answer ONE question from each Unit
All Questions Carry Equal Marks
Unit I
1. What are Distributed Systems? Explain in detail. 6M
Explain the various services provided by an operating system.
9M
2. What are System Programs? Explain various types of System Programs in detail. 8M
Discuss various multithreading models with a diagram.
7M
Unit II
3. What is Critical-Section Problem? Explain the requirements that a critical-section
problem must satisfy.
7M
Explain the solution to Readers and Writers problem using semaphores.
8M
4. Consider the following snapshot of a system.
Allocation Maximum Available
A B C A B C A B C
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
The maximum instances of resource types A B C is 10, 7.
Answer following questions using Bankers algorithm:
i. Find need matrix
ii. Is the system in safe state?
iii. If a request from P1 arrives for can the request be granted immediately?
iv. Find the new state.
9M
What is a resource allocation graph Explain how RAG is useful in describing
deadlock by considering your own example.
6M
Unit III
5. Consider the following reference string:
1
Assuming three frames, all initially empty how many page faults would occur for:
i. LRU
ii. FIFO
iii. Optimal page replacement algorithms
9M
Distinguish between:
i. First fit and best fit algorithm
ii. Paging versus segmentation
iii. Internal and external fragmentation
6M
6. What are the different file types? Give their functions along with one example for each
type.
10M
Explain different ways of accessing files. 5M
Cont…2

Unit IV
7. Explain Disk Structure in detail. 9M
Explain the important aspects which will impact the performance of tertiary-storage.
6M
8. Explain the following Disk Scheduling Algorithms in Detail:
i. C-SCAN Scheduling
ii. SSTF Scheduling
6M
Suppose that a disk drive has 5000 cylinders, numbered 0 to 4999.
The drive is currently serving a request at cylinder 143, and the previous request was at
cylinder 125. The queue of pending requests, in FIFO order, is 86, 1470, 913, 1774, 948,
1509, 1022, 1750, 130 Starting from the current head position, what is the total
distance (in cylinders) that the disk arm moves to satisfy all the pending requests, for
each of the following disk-scheduling algorithms:
i. FCFS
ii. SSTF
iii. SCAN
iv. LOOK
v. C-SCAN
9M
Unit V
9. How are the access-matrix facility and the role-based access-control facility similar?
How do they differ?
7M
Write short note on:
i. Access control
ii. Revocation of Access Rights
8M
10. List and explain various forms of accidental and malicious security violations. 9M
What commonly used computer programs are prone to man-in-the middle attacks?
Discuss solutions for preventing this form of attack.
6M