Bihar Engineering University, Patna
B.Tech 3rd Semester Examination, 2025
Operating System
Time: 03 HoursCode: 105305Full Marks: 70
Instructions:
- The marks are indicated in the right-hand margin.
- There are NINE questions in this paper.
- Attempt FIVE questions in all.
- Question No. 1 is compulsory.
Q.1 Choose the correct option/answer the following (Any seven question only):[2×7=14]
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What is the ready state of a process?
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The total number of processes completed per unit time is known as
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Physical memory is broken into fixed-sized blocks called
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The First Fit, Best Fit and Worst Fit are partitioning algorithms to select a ____
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In Paging, every logical address generated by the CPU is divided into two parts. They are ____
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Page fault occurs when
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Deadlock prevention ensures
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Which IPC mechanism requires synchronization between processes?
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User-level threads are managed by
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A process moves from Running to Ready state due to
Q.2 (a) What is dispatch latency? How does it affect Real time scheduling? Suggest some solutions to keep dispatch latency low.[7]
(b) What is a process scheduler? State the characteristics of an exemplary process scheduler.[7]
Q.3 (a) Describe the implementation of semaphores in attaining process synchronization. Explain any two classical process synchronization problems.[7]
(b) Consider a disk with 200 tracks and the queue has random requests from different processes in the order: 55, 58, 39, 18, 90, 160, 150, 38, 184. Initially arm is at 100. Find the Average Seek length using FIFO, SSTF and SCAN algorithm.[7]
Q.4 (a) Consider the set of Processes <A, B, C, D> assumed to have arrived at the time sequence <0, 1, 2, 4> having Burst time <3, 6, 4, 2> respectively. Draw the Gantt Chart illustrating their execution using Shortest Job First (SJF) Algorithm, Shortest Remaining Time First (SJF Preemptive Algorithm) and calculate the Average Turn Around time and Average waiting time for both scheduling algorithms.[7]
(b) With a neat sketch (process state diagram), explain various states the process may undergo from its creation to its termination. Mark all possible transitions and states and clearly explain the details of states and state-transitions.[7]
Q.5 (a) Consider the following snapshot of a system:[7]
| Process | Allocation A | Allocation B | Allocation C | Allocation D | Max A | Max B | Max C | Max D |
|---|---|---|---|---|---|---|---|---|
| P0 | 0 | 0 | 1 | 2 | 0 | 0 | 1 | 2 |
| P1 | 1 | 0 | 0 | 0 | 1 | 5 | 2 | 0 |
| P2 | 1 | 3 | 5 | 4 | 7 | 5 | 0 | — |
| P3 | 0 | 6 | 3 | 2 | 2 | 3 | 5 | 6 |
| P4 | 0 | 0 | 1 | 4 | 0 | 6 | 5 | 2 |
Available: A = 0, B = 6, C = 5, D = 6
Answer the following questions using the banker's algorithm: (i) What is the content of the matrix Need? (ii) Is the system in a safe state? (iii) If a request from process P1 arrives for (0,4,2,0), can the request be granted immediately?
(b) Explain the concept of paging in operating systems. Discuss the structure of logical and physical addresses, the role of the page table in address translation, and analyze the issue of internal fragmentation in paging systems.[7]
Q.6 (a) Consider the following page reference string 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2, 1, 2, 0, 1, 7, 0, 1. How many page fault would occur for the following page replacement algorithms for 3 page frame? All frames are initially empty. (i) FIFO replacement (ii) LRU (iii) Optimal replacement[7]
(b) Describe the segmentation memory management scheme in operating systems. Explain the logical address format, segment table structure, and discuss the problem of external fragmentation along with its impact on memory utilization.[7]
Q.7 (a) Explain the concept of preemptive CPU scheduling in operating systems. Discuss its working mechanism, advantages, disadvantages, and compare it with non-preemptive scheduling in terms of responsiveness and overhead.[7]
(b) Discuss the significance of time quantum in time-sharing systems. Analyze how the choice of time slice affects CPU utilization, context switching overhead, and turnaround time of processes.[7]
Q.8 (a) Explain the concept of multithreading in operating systems. Discuss the advantages of multithreading, different models of multithreading, and analyze the challenges involved in thread management such as synchronization and resource sharing.[7]
(b) In a system implementing the Readers–Writers synchronization problem, suppose there are 5 processes arriving in the following order with their arrival times (in ms) and operation durations: (i) R1: Arrival = 0, Duration = 4 (ii) W1: Arrival = 1, Duration = 3 (iii) R2: Arrival = 2, Duration = 2 (iv) R3: Arrival = 3, Duration = 3 (v) W2: Arrival = 5, Duration = 2. Assuming the first Readers–Writers problem (reader-priority) is followed: Determine the execution order of processes and compute the waiting time for each process. Also, draw the corresponding timeline (Gantt chart) showing access to the shared resource.[7]
Q.9 Write short note on any two of the following:[7×2=14]