CS-405 Operating Systems - Jun 2023 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. What are the goals of an operating system? Explain.
   How to answer

   • Define operating system as resource manager and extended machine
   • List primary goals: convenience, efficiency, ability to evolve
   • Explain user goals vs system goals
   • Explain with examples of resource abstraction
2. 7 Marks
   bDescribe the differences among short term, medium term and long term scheduling.
   How to answer

   • Define short-term CPU scheduler
   • Define medium-term swapping scheduler
   • Define long-term job scheduler
   • Compare on frequency, queue, function in table
3. 7 Marks
   aWhat is meant by system call? How it can be used. How does an application program use these call during execution?
   How to answer

   • Define system call as OS service interface
   • Explain use via trap / software interrupt
   • Explain steps: parameters, trap, kernel execution, return
   • Example of application program using read/write/fork
4. 7 Marks
   bDefine Process States. Draw the diagram of PCB.
   How to answer

   • Define process states: new, ready, running, waiting, terminated
   • Explain PCB fields: PID, state, PC, registers, memory info
   • Include neat labelled PCB / state diagram
   • Explain transitions between states
5. 7 Marks
   aSuppose that a disk drive has 200 cylinders, numbered 0 to 199. The work queue is: 23, 89, 132, 42, 187. Determine the total distance for the following disk scheduling algorithms:

   1. i)Scan
   2. ii)Look
   How to answer

   • State disk parameters: 200 cylinders 0-199, queue 23, 89, 132, 42, 187
   • Apply SCAN head movement and sum seek distances
   • Apply LOOK head movement and sum seek distances
   • Compare total head movement for both algorithms
6. 7 Marks
   bList the advantages and disadvantages of Magnetic Tape memory.
   How to answer

   • Define magnetic tape memory
   • List advantages: low cost, high capacity, portability
   • List disadvantages: sequential access, slow, environmental sensitivity
   • Conclude with use as backup/archival
7. 7 Marks
   aExplain in detail about various ways of free space management.
   How to answer

   • Define free space management need
   • Explain bit vector / bitmap method
   • Explain linked list, grouping, counting methods
   • Compare with examples and diagram
8. 7 Marks
   bWhat is the difference between threads and process.
   How to answer

   • Define process vs thread
   • Compare on memory, overhead, sharing, scheduling
   • Give examples of multithreading vs multiprocessing
   • Present differences in tabular form
9. 7 Marks
   aExplain paging and segmentation. How are they helpful in removing fragmentation?
   How to answer

   • Define paging with page tables and frames
   • Define segmentation with segments and descriptors
   • Explain internal vs external fragmentation
   • Explain how paging removes external and segmentation aids logical division
10. 7 Marks
    bWhat do you mean by deadlock prevention? A computer has six tape drive with a processes competing for them. Each process need two tape drives for which values of n the system is deadlock free.
    How to answer

    • Define deadlock prevention concept
    • State condition: total resources 6 tape drives, need 2 per process
    • Apply deadlock-free condition to find max n
    • Conclude safe value of n
11. 7 Marks
    aExplain mutual exclusion with suitable example.
    How to answer

    • Define mutual exclusion for critical section
    • State requirements: mutual exclusion, progress, bounded wait
    • Give example of two processes sharing printer/variable
    • Explain software/hardware solution briefly
12. 7 Marks
    bDiscuss Reader-Writers solution using Monitors.
    How to answer

    • Define Reader-Writers problem
    • Define monitor with condition variables
    • Show monitor procedures for reader and writer
    • Explain how synchronization avoids starvation
13. 7 Marks
    aExplain file system used in Linux and Windows.
    How to answer

    • List Linux file systems: ext2/ext3/ext4
    • List Windows file systems: FAT, NTFS
    • Compare features: journaling, permissions, max size
    • Give examples of use
14. 7 Marks
    bWhat is a file? Briefly explain different directory structures. What kind of directory structure is used in UNIX?
    How to answer

    • Define file as collection of related information
    • Explain directory structures: single, two-level, tree, acyclic, general graph
    • Describe UNIX tree-structured directory
    • Give diagram of directory hierarchy
15. 4 Marks
    aWrite short notes: Concurrent Programming
    How to answer

    • Define concurrent programming
    • Explain processes/threads interleaving
    • Mention synchronization issues
    • Give example
16. 4 Marks
    bWrite short notes: Virus
    How to answer

    • Define virus in OS context
    • Explain types and infection mechanism
    • Mention protection measures
    • Give example
17. 3 Marks
    cWrite short notes: Remote Procedure Call (RPC)
    How to answer

    • Define RPC concept
    • Explain stub, marshalling, communication steps
    • Mention advantages for distributed systems
    • Give example
18. 3 Marks
    dWrite short notes: Time Sharing
    How to answer

    • Define time sharing system
    • Explain time slice / quantum sharing
    • Mention advantages for interactive users
    • Give example