NEC B.Tech (R20) 3-1 Operating System Important Questions

UNIT-I (Computer System and Operating System Overview)

1. What is Operating System? What are various functions of operating system? Explain.

2.  Explain different types of operating systems.

3. Differences between hard and real time operating systems

4. With neat sketch write about different architectures of operating system.

5. Write the difference between the function and system call. Briefly explain the six major categories of system calls

6. Write about different generations of operating system.

UNIT-II ( Process Management and Process scheduling)

1.  Define process? Explain process state diagram and PCB?

2. Explain the process scheduling with a neat queuing diagram.

3. What are the advantages of inter-process communication? How communication takes place in a shared-memory environment? Explain.

4. Explain in detail the two popular inter-process communication mechanisms.

5. Explain typical elements of inter process communication models.

6. What are the differences between user-level threads and kernel-level threads?

7. Discuss how the following pairs of scheduling criteria conflict in a certain settings.

i) CPU utilization and response time, ii) Average turnaround time and maximum waiting time, and  

iii) I/O device utilization and CPU utilization.

8. Explain the Round Robin scheduling algorithm with a suitable example.

9.  Consider the following four processes represented as (Process, Arrival Time, Burst Time) with the length of CPU burst in milliseconds. { ( P1, 0, 10), (P2, 1, 7), (P3, 2, 13), (P4, 3, 11) }. Using preemptive SJF scheduling: i) Draw Gantt chart. ii) Calculate average waiting time

10. For the processes listed below, evaluate Average Waiting Time and Average Turnaround Time for: i) FCFS ii) SJF iii) SRT iv) Non-Preemptive Priority v) Preemptive Priority vi) RR(Q=2)

11.  illustrate the Belady’s Anomaly for the reference string: 5 0 1 2 0 3 0 4 2 3 0 32 1 2 0 1 5 0 1 2.

12. Write and explain various scheduling criteria’s with respect CPU scheduling. And show the calculations for at least 5 processes arriving at consecutive intervals.

UNIT-III ( Concurrency and Memory management) 

A) Concurrency control 

1. What is a Critical Section problem? Give the conditions that a solution to the critical section problem must satisfy.

2. What is critical section problem? Write and explain Peterson’s solution for it

3. What happens if the wait() and signal() semaphore operations are not executed atomically? Give explanation.

4. Discuss Mutual-exclusion implementation with Test And Set () instruction.

5. What is a monitor? How are monitors used in solving the Dining Philosophers Problem ?

6. How does the signal() operation associated with monitors differ from the corresponding operation defined for semaphores.

7. What is semaphore? Why it is important? Suggest the solution for bounded buffer problem with semaphores.

B) Memory Management 

1. What is paging? Explain the hardware support given for paging.

2. What is paging? Explain its structure for 32 -byte memory with 4-byte pages.

3. What is effective access time? Compute it for 70% hit ratio, 20 ns to search TLB and 100 ns to access memory. Observe the difference when it is changed to 90% hit ratio

4. What is a page fault? Explain the steps involved in handling a page fault with a neat sketch.

5. Explain the process of converting virtual addresses to physical addresses with a neat diagram.

6. How demand paging affects the performance of a computer system? Give explanation.

7. Explain the difference between External fragmentation and Internal fragmentation. How to solve the fragmentation problem using paging.

8. Given memory partitions of 500 KB, 100 KB, 200 KB, 300 KB, and 600 KB (inorder), how would each of the first-fit, best-fit, and worst-fit algorithms place processes of 212 KB, 417 KB, 112 KB and 426 KB (in order)? Which algorithm makes the most efficient use of memory?

9. Compare the main memory organization schemes of continuous memory allocation, pure segmentation, and pure paging with respect to the following issues: i) External fragmentation,

 ii) Internal fragmentation, iii) Ability to share code across the process

UNIT-IV (Virtual Memory and Principles of Deadlock)

A) Virtual Memory 

1. Consider the following page reference string: 1,2,4,7,3,5,6,3,6,1,4,2,3,6,5,2 How many page faults would occur for the optimal page replacement algorithm, assuming four frames and all frames are initially empty.

2. Consider the following page reference string 2,3,4,5,3,2,6,7,3,2,3,4,1,7,1,4,3,2,3,4,7. Calculate the number of page faults with LRU, FIFO and optimal page replacement algorithms with frame size of 3.

3. How does the system detect Thrashing? What can the system do to eliminate this problem? Explain.

4. Consider the reference string: 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2, 1, 2, 0, 1, 7, 0, 1 for a memory with three frames. Trace FIFO, optimal, and LRU page replacement algorithms.

B) Principles of dead lock

5. What is a deadlock? How deadlocks are detected?

6. Discuss various techniques to recover from the deadlock.

7. How to prevent necessary and sufficient conditions of deadlock? Explain.

8.  What are the necessary conditions for a Deadlock? Discuss.

9. Consider the following and find out the possible resource allocation sequence with the help of deadlock detection algorithm processes: p0, p1, p2, p3, p4, Resources A, B, C Allocation [0 1 0, 2 0 0 , 3 0 3, 2 1 1, 0 0 2] Max[0 0 0, 2 0 2, 0 0 0, 1 0 0, 0 0 2] Available[0 0 0].

10. Explain the following deadlock avoidance algorithms :i) Banker’s algorithm ii) Safety algorithm.

UNIT-V (File System and Disk scheduling) 

1 Explain different File Attributes and File Operations.

2. Discuss different RAID structures

3. Explain the following concepts with respect to file:  i) File operations ii) File Structures iii) File Types

4. Discuss in detail the file allocation techniques: Sequential, Indexed and Linked

5. Briefly explain about single-level, two-level and Tree-Structured directories.

6. Explain and compare the FCFS and SSTF disk scheduling algorithms.

7. Discuss in detail about different file access methods.

Differentiate SCAN, C-SCAN and LOOK, C-LOOK disk scheduling algorithms with an example