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. The main task of Kernel layer in operating system is to handle
(A) Segmentation and paging (B) Data blocks
(C) File and devices (D) Process and Semaphores
b. Most computer systems have small piece of code stored in ROM known as
(A) Compiler (B) Bootstrap program
(C) Byte code (D) Linker
c. Thread is a basic unit of execution of CPU utilization and is sometimes called
(A) Heavy weight process
(B) Virtual weight process
(C) Light weight process
(D) Dummy weight process
d. The solution to critical section problem uses a Synchronization tool called
(A) Semaphore (B) Scheduling
(C) Atomicity (D) Event-handling
e. A variant of resource-allocation-graph used for single instance resources in deadlock detection algorithm is
(A) Process-graph (B) Resource graph
(C) Wait-for graph (D) Isomorphic-graph
f. An optimal page replacement has
(A) High page fault rate and never suffer from Belady’s anomaly
(B) Low page fault rate and always suffer from Belady’s anomaly
(C) High page fault rate and always suffer from Belady’s anomaly
(D) Low page fault rate and never suffer from Belady’s anomaly
g. File Allocation Table (FAT) is used in
(A) MS-DOS (B) Both (A) and (C)
(C) OS/2 (D) Unix
h. In I/O devices, the host repeatedly reads the busy bit until that bit becomes clear. This process is known as
(A) Masking (B) Interrupting
(C) Polling (D) Exception handling
i. In Windows 2000 all processor dependent code is isolated in a dynamic link library (DLL) called
(A) Kernel System (B) Network File System
(C) Hardware Abstraction Layer (D) Object Manager
j. In soft-real time scheduling, which one of the following is valid:
(A) Critical processes receive priority over less fortunate process
(B) Critical process to complete in a guaranteed amount of time
(C) Critical process to preempt all process
(D) Critical process to have resource reservation.
Answer any FIVE Questions out of EIGHT Questions.
Each question carries 16 marks.
Q.2 a. What are the various types of services provided by Kernel to I/O subsystem? Explain any four features. (8)
b. Explain various types of file access methods. (8)
Q.3 a. Explain the following:
(i) Suppose that a scheduling algorithm (at the level of short-term CPU scheduling) favors those processes that have used the least processor time in the recent past. Why will this algorithm favor I/O-bound programs and yet not permanently starve CPU-bound programs? (4)
(ii) Difference between preemptive and nonpreemptive scheduling. (4)
b. Define the following (8)
(i) Multithreading (ii) Multitasking
(iii) Multiprocessing (iv) Multiprogramming
Q.4 a. Distinguish between Network Operating Systems and Distributed Operating Systems. (4)
b. (i) Explain logical and low-level formatting. (4)
(ii) Give the advantages of RAID structure. There are six levels in RAID structure. Give the functionality of each level. (2+6)
Q.5 a. What is the cause of thrashing? How does the system detect thrashing? Once it detects thrashing, what can the system do to eliminate this problem? (3)
b. Consider the following page reference string:
1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6
How many page faults would occur for the following replacement algorithms, assuming two, five, and seven frames? Remember all frames are initially empty, so the first unique pages will all cost one fault each. (9)
(i) LRU replacement (ii) FIFO replacement
(iii) Optimal replacement
c. What is fragmentation? Explain internal and external fragmentation by taking a suitable example. (4)
Q.6 a. (i) What are necessary conditions for deadlock situation to arise? (4)
(ii) Explain various techniques to recover from a deadlock. (4)
b. Consider the following snapshot of a system in the context of Banker’s algorithm for deadlock avoidance, where the resources have several instances
Allocation Max Available
A B C D A B C D A B C D
P0 2 3 1 4 3 5 2 4 2 0 3 1
P1 1 1 0 2 2 1 3 4
P2 0 1 2 1 2 2 2 6
P3 0 0 2 1 2 0 3 2
P4 2 0 1 3 5 1 1 3
Answer the following questions using the Banker’s algorithm:
(i) What is the content of the matrix Need? (3)
(ii) Is the system in a safe state? Give complete computation and sequence of allocation. (5)
Q.7 a. Explain techniques in Caching Update Policy used in distributed systems. (6)
b. (i) Explain the functionality of Election algorithm. (2)
(ii) Describe briefly various types of election algorithms (8)
Q.8 a. Explain the following threading issues (8)
(i) Thread Cancellation (ii) Signal handling using threads
b. Explain various types of Inter Process Communication techniques (8)
Q.9 a. Draw the architectural block diagram of Linux System and explain the functionality of various components. (8)
b. (i) In a dynamic protection system, access rights are to be revoked. What are the various types of problem that encounter? (4)
(ii) What are the various types of schemes that implement revocation of capabilities in protection systems? (4)