AMIETE – CS (OLD SCHEME)
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 the best alternative in the following: (2
10)
a. The only state transition that is initiated by the user process itself is?
(A) Wakeup (B) Dispatch
(C) Block (D) All of the above
b. At a particular time, the value of a counting semaphore is 10. It will become 7 after.
(A) 4 P operation
(B) 3 V operation
(C) 13 P operation and 10 V operation
(D) 13 V operation and 10 P operation
c. Which of the following page replacement algorithm suffers from Belady’s anomaly?
(A) LRU
(B) FIFO
(C) Optimal Replacement
(D) None of the above
d. The security component(s) used in Microsoft Windows 2000© Operating system is
(A) LSA (B) Kerberos V5
(C) NTLM (D) All of these
e. A scheduling discipline is said to be ________if all similar processes are treated the same, and no process can suffer indefinite postponement due to scheduling issues.
(A) Predictable (B) Scalable
(C) Fair (D) Portable
f. Noncontiguous memory allocation splits programs into blocks of memory called ________ that can be loaded into nonadjacent “holes” in main memory
(A) Pages (B) Partitions
(C) Frames (D) Segments
g. Public-key cryptography is symmetric in that ________.
(A) it decrypts messages using the same key it uses to encrypt
(B) both the sender and the receiver use the same key
(C) it employs two inversely related keys
(D) either host can create a key and both hosts can use it
h. ________ is not one of Linux’s primary subsystems?
(A) Process management (B) Virtual file system
(C) Networking (D) Inter process communication
i. ‘j’ processes share ‘k’ resources of the same type. The maximum need of each process does not exceed ‘k’ and the sum all their maximum needs is always less than j+k. In this scenario
(A) Deadlock can never occur (B) Deadlock has to occur
(C) Deadlock may occur (D) none of the above
j. If there are 32 segments, each of size 1 kbyte, then the logical address should have
(A) 32 bits (B) 14 bits
(C) 15 bits (D) 16 bits
Answer any FIVE Questions out of EIGHT Questions.
Each question carries 16 marks.
Q.2 a. What are the three main purposes of an operating system?
Define the essential properties of (i) Batch (ii) Interactive (iii) Time sharing and (iv) Real time operating systems. (8)
b. Compare the use of networking sockets with the use of shared memory as a mechanism for communicating data between processes on a single computer. What are the advantages of each method? When might each be preferred? (8)
Q.3 a Explain the four components of a computer system. (8)
b. (i) What is the main advantage of the layered approach to system design? (4)
(ii) What is the main advantage for an operating-system designer of using a virtual-machine architecture? What is the main advantage for a user? (2)
(iii) List system service functions provided for efficient operation of the system. (2)
Q.4 a. (i) Explain various process states. (3)
(ii) What do you mean by interprocess communication? Explain various methods of interprocess communication. (5)
b. (i) What are the differences between user-level threads and kernel threads? Under what circumstances is one type better than the other? (5)
(ii) Explain two situations in which multithreading provides better performance than a single-threaded solution (3)
Q.5 a. (i) A CPU scheduling algorithm determines an order for the execution of its scheduled processes. Given n processes to be scheduled on one processor, how many possible different schedules are there? Give a formula in terms of n. (2)
(ii) 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? (3)
(iii) What advantage is there in having different time-quantum sizes on different levels of a multilevel queuing system? (3)
b. Consider the table of processes shown below. Calculate the turnaround time and waiting time for each process if Round Robin scheduling is used with a time slice of 1 unit and 5 units. (8)
|
Process |
Arrival Time |
Processing Time |
|
A |
0 |
1 |
|
B |
1 |
5 |
|
C |
2 |
1 |
|
D |
3 |
5 |
Q.6 a. Define Semaphores. How can it be used as a general synchronization tool? What advantage does a semaphore have as compared to a hardware test-and-set instruction? (8)
b. Explain the four necessary conditions that must be in effect for a deadlock to exist. Explain two methods for handling deadlocks. (8)
Q.7 a. Under what circumstances do page faults occur? Describe the actions taken by the operating system when a page fault occurs. (8)
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 (1) LRU replacement (2) FIFO replacement algorithms, assuming one, two, three, four, five, six, or seven frames? Suppose that all frames are initially empty. (8)
Q.8 a. (i) Consider a system that supports the strategies of contiguous, linked and indexed allocation. What criteria should be used in deciding which strategy is best utilized for a particular file? (3)
(ii) Why is rotational latency usually not considered in disk scheduling? How would you modify SSTF, SCAN, and C-SCAN to include latency optimization? (5)
b Given memory partitions of 100K, 500K, 200K, 300K, and 600K (in order), how would each of the First-fit, Best-fit, and Worst-fit algorithms place processes of 212K, 417K, 112K, and 426K (in order)? Which algorithm makes the most efficient use of memory? (8)
Q.9 a. (i) State advantages and disadvantages of placing functionality in a device controller, rather than in the kernel. (3)
(ii) What are the main differences between capability lists and access lists? (2)
(iii) Contrast the various network topologies in terms of reliability. (3)
b. (i) Consider a system where every process can send a message to every other process in the system. Explain the election of a new coordinator in case of failures (5)
(ii) Explain the device class abstractions used in LINUX operating system (3)