AL-501 Operating Systems - Jun 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
   aWhat is real time operating system? What is difference between hard real time and soft real time operating system?
   How to answer

   • Define real time operating system with time-constraint response
   • Characteristics: determinism, responsiveness, deadlines
   • Define hard real time with missed deadline = failure + examples
   • Define soft real time with degraded performance + examples
   • Tabular differences on deadline, predictability, applications
2. 7 Marks
   bWhat is spooling? What are the advantage of spooling over buffering?
   How to answer

   • Define spooling - Simultaneous Peripheral Operations On-Line
   • How spooling uses disk as large buffer/queue
   • Define buffering and its limited size
   • Advantages: concurrency, job queuing, device utilization
   • Comparison table spooling vs buffering
3. 7 Marks
   aWhat is kernel? Describe various operations performed by kernel?
   How to answer

   • Define kernel as core of OS in privileged mode
   • Role in system calls, resource management
   • List operations: process, memory, device, interrupt, system call handling
   • Brief explanation of each operation
4. 7 Marks
   bDescribe classification of operating system.
   How to answer

   • List types: batch, multiprogramming, time-sharing, real-time, distributed, network, mobile
   • Brief characteristics of each type
   • Classification criteria diagram/tree
   • Examples of each class
5. 7 Marks
   aDefine semaphore? Give a scheme for implementation of semaphore primitives?
   How to answer

   • Define semaphore as integer synchronization variable
   • Define wait/P and signal/V primitives
   • Busy-wait vs blocking implementation with queue
   • Pseudocode for wait and signal with atomicity
6. 7 Marks
   bDefine message passing and shared memory interprocess communication?
   How to answer

   • Define IPC need for cooperation
   • Define message passing: send/receive, direct/indirect
   • Define shared memory: common address region
   • Compare buffering, synchronization, speed
7. 7 Marks
   aWhat is the difference between pre-emptive and non preemptive scheduling, state why strict non preemptive scheduling is unlikely to be used in computer center? Explain the operation of multi level scheduling?
   How to answer

   • Define preemptive vs non-preemptive with CPU control
   • Comparison on response, starvation, overhead
   • Why strict non-preemptive unsuitable: long jobs block, no priority response
   • Explain multilevel queue and multilevel feedback queue operation
8. 7 Marks
   bWhat do you understand by context switching and various processes involved in it?
   How to answer

   • Define context switching as saving/restoring PCB state
   • Contents saved: PC, registers, memory maps
   • Steps: interrupt, save state, scheduler, restore state
   • Overhead and performance impact
9. 7 Marks
   aDescribe Dekker's solution?
   How to answer

   • State mutual exclusion problem for two processes
   • Introduce flag and turn variables
   • Present Dekker's algorithm entry/exit code
   • Prove mutual exclusion, progress, bounded wait
10. 7 Marks
    bState and describe the producer consumer problem with its suitable solution?
    How to answer

    • State bounded-buffer producer-consumer problem
    • Explain race on full/empty buffer
    • Semaphore solution: mutex, empty, full with wait/signal
    • Producer and consumer pseudocode
11. 7 Marks
    a

    Consider the process CPU burst time and arrival time given below:

    Process	CPU Burst Time	Arrival Time
    $p_1$	$8$	$0$
    $p_2$	$4$	$1$
    $p_3$	$9$	$2$
    $p_4$	$5$	$3$

    Draw the Gantt chart and calculate the following by using SRTF CPU scheduling algorithms

    1. i)average waiting time
    2. ii)average turnaround time
    How to answer

    • List given burst times and arrival times for p1-p4
    • Apply SRTF preemption timeline and draw Gantt chart
    • Compute completion, turnaround and waiting times per process
    • Calculate averages: average waiting time and average turnaround time
12. 7 Marks
    bDiscuss and explain Bankers algorithm for avoidance of deadlock?
    How to answer

    • Define deadlock avoidance vs prevention
    • Explain Banker's data structures: Available, Max, Allocation, Need
    • Describe safety algorithm and resource-request algorithm steps
    • Illustrate with example safe sequence
13. 7 Marks
    aGiven memory partition 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 algorithms make the most efficient use of memory?
    How to answer

    • List partitions 100k, 500k, 200k, 300k, 600k and requests 212k, 417k, 112k, 426k
    • Simulate first-fit, best-fit, worst-fit placements in order
    • Identify unallocated processes per algorithm
    • Conclude which algorithm uses memory most efficiently
14. 7 Marks
    bDiscuss the paging hardware with TLB?
    How to answer

    • Define paging and page table translation
    • Role of TLB as fast associative cache
    • Steps: TLB hit vs TLB miss with page table access
    • Diagram of CPU-TLB-page table-physical memory with effective access time
15. 7 Marks
    aDiscuss Disk scheduling algorithms?
    How to answer

    • Define disk scheduling need for seek optimization
    • Explain FCFS, SSTF, SCAN, C-SCAN, LOOK, C-LOOK
    • Compare performance, starvation, throughput
    • Example seek sequence for each
16. 7 Marks
    bDiscuss free space management in disk, explain following term:

    1. i)Bit vector
    2. ii)Linked list
    3. iii)Grouping
    4. iv)Counting
    How to answer

    • Define free space management need
    • Explain bit vector, linked list, grouping, counting
    • Advantages/disadvantages of each method
    • Example structures for each technique