IT-501 Operating System - Dec 2025 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aDefine an Operating System. Explain its objectives and major services provided by an OS.
   How to answer

   • Define operating system as resource manager and extended machine
   • State objectives: convenience, efficiency, resource management, protection
   • List major services: process, memory, file, I/O, protection, networking, UI
2. 7 Marks
   bDescribe different types of Operating Systems with suitable examples.
   How to answer

   • List types: batch, time-sharing, distributed, real-time, network, mobile
   • Explain characteristics of each type
   • Give suitable example for each e.g., UNIX, Windows, VxWorks
3. 7 Marks
   aExplain the structure of an Operating System. Discuss system calls and their importance.
   How to answer

   • Explain OS structure: monolithic, layered, microkernel, modular
   • Define system call and its mechanism trap to kernel
   • Discuss types of system calls and importance for OS-user interface
4. 7 Marks
   bExplain OS design and implementation issues. What is spooling and buffering?
   How to answer

   • Discuss design goals: user goals and system goals, mechanisms vs policies
   • Explain implementation issues: language, structure, performance
   • Define spooling and buffering with differences and examples
5. 7 Marks
   aExplain CPU scheduling criteria and different CPU scheduling algorithms.
   How to answer

   • List scheduling criteria: CPU utilization, throughput, turnaround, waiting, response
   • Explain preemptive vs non-preemptive scheduling
   • Describe FCFS, SJF, Priority, Round Robin algorithms
6. 7 Marks
   b

   Consider the following processes with arrival time 0:

   Process	Burst Time
   P1	5
   P2	3
   P3	8

   Calculate the average waiting time using FCFS scheduling.

   How to answer

   • Draw Gantt chart for FCFS order P1, P2, P3 with arrival 0
   • Calculate waiting time for each: 0, 5, 8
   • Compute average waiting time = (0+5+8)/3 = 4.33
7. 7 Marks
   aExplain process concept and operations on processes.
   How to answer

   • Define process, process states and PCB
   • Explain process creation and termination operations
   • Describe process scheduling, context switch and IPC operations
8. 7 Marks
   bExplain critical section problem and semaphores.
   How to answer

   • Define critical section and its requirements: mutual exclusion, progress, bounded wait
   • Explain semaphore types: binary and counting, wait and signal
   • Discuss solution to critical section using semaphores
9. 7 Marks
   aExplain the deadlock and its necessary conditions.
   How to answer

   • Define deadlock with example of resource waiting
   • List four Coffman necessary conditions
   • Explain each condition: mutual exclusion, hold and wait, no preemption, circular wait
10. 7 Marks
    bDescribe deadlock prevention, avoidance, and detection techniques.
    How to answer

    • Explain prevention by negating one of four conditions
    • Explain avoidance using safe state and Banker's algorithm
    • Explain detection using wait-for graph and recovery methods
11. 7 Marks
    aExplain memory management techniques including fixed and dynamic partitioning.
    How to answer

    • Define contiguous memory management and fragmentation
    • Explain fixed partitioning with internal fragmentation
    • Explain dynamic partitioning with external fragmentation and compaction
12. 7 Marks
    bGiven memory blocks of sizes 100 KB, 500 KB, 200 KB, and 300 KB, allocate a process of size 212 KB using First-Fit and Best-Fit algorithms.
    How to answer

    • Apply First-Fit: scan in order, allocate 212 KB to 500 KB block
    • Apply Best-Fit: select smallest sufficient block, 300 KB block
    • Compare leftover fragmentation in both cases
13. 7 Marks
    aExplain virtual memory and demand paging.
    How to answer

    • Define virtual memory and its benefits
    • Explain demand paging concept with valid-invalid bit and page fault
    • Describe steps of page fault handling
14. 7 Marks
    bExplain page replacement algorithms and the concept of thrashing.
    How to answer

    • Explain FIFO, LRU, Optimal page replacement algorithms
    • Define thrashing and its causes
    • Discuss working set model to control thrashing
15. 7 Marks
    aExplain disk scheduling and different disk scheduling algorithms.
    How to answer

    • Define disk scheduling and performance parameters seek time, latency
    • Explain FCFS, SSTF, SCAN, C-SCAN, LOOK algorithms
    • Compare algorithms with example movement
16. 7 Marks
    bExplain file management in Operating System. Discuss file organization and access methods.
    How to answer

    • Define file management and file attributes/operations
    • Explain file organization: sequential, indexed, direct
    • Discuss access methods: sequential, direct, indexed sequential