2080
Bsc CSIT / Semester 4 / Science
Computer Science and Information Technology
Operating System
Full Marks: 60 + 20 + 20
Pass Marks: 24 + 8 + 8
Time: 3 Hours
Candidates are required to give their answers in their own words as far as practicable.
The figures in the margin indicate full marks.
Attempt any TWO question.
When does the request switch from user mode to kernel mode? Give answer with an example. Find the average waiting time and turnaround time for the process scheduling algorithms FCFS, Priority and RR (Quantum=2) in the following given dataset.
| Process | Arrival Time | Burst Time | Priority |
|---|---|---|---|
| P0 | 0 | 5 | 1 (Lowest) |
| P1 | 1 | 3 | 4 (Highest) |
| P2 | 2 | 8 | 2 |
| P3 | 3 | 6 | 3 |
How do you recognize critical section? Why do we need to synchronise it? Consider the request for the page references Find the number of page fault for FIFO and LRU with 4 page frames.
Can deadlock occur in case of preemptive resources? List the conditions for deadlock. Define allocation graph with example.
Attempt any EIGHT question.
Explain different memory allocation strategies.
Suppose a disk has 201 cylinders, numbered from 0 to 200. At same time the disk arm is at cylinder 10, and there is a queue of disk access requests for cylinders and . Find the total seek time for the disk scheduling algorithm FCFS and SSTF. Assume the head is moving inward.
What are the advantages of using interrupt? Describe.
Differentiate between contiguous and linked list file allocation technique.
Differentiate between paging and segmentation.
What does Belady’s anomaly mean? What are the benefits of multiprogramming over uniprogramming?
How can we achieve mutual exclusion? Describe.
What makes thread different with process? Draw the transition diagram between states of a process.
When does a page fault ocur? Give a structure of a page table.
*** END OF QUESTION PAPER ***
1. User Mode → Kernel Mode Transition Definition: - CPU operates in two modes: 1. User Mode: Limited access; cannot execute privileged instructions. 2. Kernel Mode: Full access to hardware a
1. Critical Section Definition: - A critical section (CS) is a part of a program where shared resources (like variables, memory, files, or devices) are accessed or modified. Recognition: - Section
1. Deadlock with Preemptive Resources Definition of Deadlock: - Deadlock is a situation in which two or more processes are waiting indefinitely for resources held by each other, and none can proceed
Memory Allocation Strategies Memory allocation strategies determine how processes are assigned memory in the system. 1. Contiguous Memory Allocation - Each process occupies a single contiguous block
Disk Scheduling Example Given: - Disk cylinders = 0 to 200 - Current head position = 10 - Request queue: 30, 85, 90, 100, 105, 110, 135, 145 - Head moving inward (toward lower cylinder numbers)
And more questions available on this page.