This set of MCQ(multiple choice questions) focuses on the NPTEL Operating System Fundamentals Week 12 Assignment Solutions.
You should practice these questions to improve Operating System Fundamentals needed for various interviews (like company interview, campus interview, walk-in interview), entrance exams, placements and other competitive exams. All the questions in this particular section are based on only “NPTEL Operating System Fundamentals Week 12 Assignment Solutions“.
Week 1: Introduction
Week 2: Processes and Threads – Part I
Week 3: Processes and Threads – Part II
Week 4: Inter-process Communication
Week 5: Concurrency and Synchronization – Part I
Week 6: Concurrency and Synchronization – Part II
Week 7: Deadlock
Week 8: CPU Scheduling
Week 9: Memory Management
Week 10: Virtual Memory – Part I
Week 11: Virtual Memory – Part II
Week 12: File System Processes and Threads – Part I
Operating System Fundamentals NPTEL 2022 Week 12 Assignment Solutions
Q1. A disk has 300 cylinders (0 to 299). If the initial position of the read-write head is at cylinder 101, calculate the total head movement following SSTF policy for the read request sequence: 123, 45, 197, 87, 250, 198, 280.
a) 425
b) 415
c) 442
d) None of the other options
Answer: d) None of the other options
Q2. A disk has 300 cylinders (0 to 299). If the initial position of the read-write head is at cylinder 101, moving towards the higher end of the disk, calculate the total head movement following C-LOOK policy for the read request sequence: 123, 45, 197, 87, 250, 198, 280.
a) 456
b) 450
c) 458
d) 445
Answer: a) 456
Q3. In the which of the following algorithm, the disk arm starts at one end of the disk and moves toward the other end, servicing requests till the other end of the disk. At the other end, the direction is reversed and servicing continues.
a) LOOK
b) SCAN
c) C-SCAN
d) C-LOOK
Answer: b) SCAN
Q4. The time taken for the desired sector to rotate to the disk head is called –
a) positioning time
b) random access time
c) seek time
d) rotational latency
Answer: d) rotational latency
Q5. What is the primary reason that a translation lookaside buffer (TLB) is used?
a) A TLB ensures that a process does not access memory outside of its address space
b) A TLB makes translating virtual addresses to physical addresses faster
c) A TLB allows multiple processes to share the L1 cache
d) A TLB makes translating virtual addresses to physical addresses possible
Answer: b)
Q6. Which of the following is NOT a way to make file systems faster?
a) Put parts of a file on many different tracks so part of it can be accessed no matter where the disk head is.
b) Cache frequently used blocks in memory so they can be accessed at memory speeds instead of disk speeds.
c) Use a disk scheduling algorithm to minimize the distance between seeks.
d) Put frequently used files or directories near the center of the disk so on average they won’t be far from the read head.
Answer: a)
Q7. For a system that performs heavy load on the disk, which of the following disk scheduling algorithms is more suited?
a) C-LOOK
b) SSTF
c) C-SCAN
d) FCFS
Answer: c) C-SCAN
Q8. Consider an operating system capable of loading and executing a single sequential user process at a time. The disk head scheduling algorithm used in First Come First Served(FCFS). If FCFS is replaces by Shortest Seek Time First (SSTF) and the vendor claims 50% better benchmark results. What is the expected improvement in the I/O performance of user programs?
a) 50%
b) 100%
c) 25%
d) 0%
Answer: d) 0%
Q9. Consider a typical disk that rotates at 15000 rotations per minute(RPM) and has a transfer rate of 50 x 106 bytes/sec. If the average seek time of the disk is twice the average rotational delay and the controller’s transfer time is 10 times the disk transfer time, the average time (in milliseconds) to read or write a 512-byte sector of the disk(in milliseconds) is-
a) 6.0
b) 6.1
c) 6.2
d) 6.3
Answer: b) 6.1
Q10. Which of the following are problems of contiguous allocation –
a) Finding space for a new file
b) External fragmentation
c) Compaction requirement
d) All of the above
Answer: b) External fragmentation
Q11. Match the following columns according to the most accurate disk-
a) I-P, II-Q, III-R
b) I-Q, II-P, III-R
c) I-R, II-P, III-Q
d) None of the above
Answer: a) I-P, II-Q, III-R
Previous Course – Week 12 Assignment Solutions
Q1. If we want to set the following protection for a file, what should be the command for it?
| R | W | X | |
| Public | 1 | 0 | 0 |
| Group | 1 | 0 | 1 |
| Owner | 1 | 1 | 1 |
a. chmod 157 file_name
b. chmod 457 file_name
c. chmod 754 file_name
d. chmod 751 file_name
Ans. c
Q2. Which of the following directory organization links are used to point to both files and
subdirectories?
a. General graph directory
b. Acyclic graph directory
c. Tree-structured directory
d. None of the above
Ans. b
Q3. In sequential access method, how the file pointer is affected by read_next() or write_next() command?
a. It is incremented to the next value
b. It is reduced to the previous value
c. It resets to the 0
d. None of the above
Ans. a
Q4. Peterson’s solution is good algorithm soIn open file locking system, the advisory access policy-
a. Denies the access request depending on the lock held and requested
b. Allows the access request ignoring the lock status
c. The processes look up the status of lock and decide what to do
d. None of the above
Ans. c
Q5. Which of the following disk scheduling algorithm should NOT be picked for systems that place heavy load on the disk?
a. SCAN
b. C-SCAN
c. SSTF
d. All of the above
Ans. c
Q6. Which of the following disk scheduling algorithm searches in only one direction and the arm goes only as far as the last request before reversing its direction?
a. LOOK
b. C-LOOK
c. SCAN
d. C-SCAN
Ans. b
Q7.
A disk has 200 cylinders (0 to 199). If the initial position of the read-write head is at cylinder 39, calculate the total head movement following SSTF policy for the read request sequence:
25, 112, 84, 188, 2, 154.
a. 233
b. 223
c. 189
d. 179
Ans. b
Q8. A disk has 200 cylinders (0 to 199). If the initial position of the read-write head is at cylinder 39, calculate the total head movement following C-LOOK policy for the read request sequence: 25, 112, 84, 188, 2, 154.
a. 358
b. 368
c. 278
d. 288
Ans. a
Q9. Which of the following is correct about linked allocation?
a. Each block contains pointer to next block
b. Locating a block can take many I/Os and disk seeks
c. Reliability issue arises when one of the pointers gets corrupted
d. All of the above
Ans. d
Q10. Select the correct statement about indexed allocation.
a. Each of the files has its own index block of pointers to its data blocks
b. Can be accomplished with multilevel index method
c. Dynamic access is possible without external fragmentation
d. All of the above
Ans. d)
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