Section-A
Process Management: Process concept, process scheduling, operation on processes; CPU scheduling, scheduling criteria, scheduling algorithms -First Come First Serve (FCFS), Shortest-Job-First (SJF), Priority Scheduling, Round Robin(RR), Multilevel Queue Scheduling.
Section-B
Memory Management: Logical & Physical Address Space, swapping, contiguous memory allocation, non-contiguous memory allocation paging and segmentation techniques, segmentation with paging; virtual memory management - Demand Paging & Page- Replacement Algorithms; Demand Segmentation.
Section-C
File System: Different types of files and their access methods, directory structures, various allocation methods, disk scheduling and management and its associated algorithms, Introduction to distributed file system.
Process-Synchronization & Deadlocks: Critical Section Problems, semaphores; methods for handling deadlocks-deadlock prevention, avoidance & detection; deadlock recovery.
Section - D Unix System And Windows NT Overview
IMPORTANT QUESTIONS (SECTION-WISE)
SECTION-A (PROCESS MANAGEMENT)
Q1. Describe the following:
(a) Short term scheduler (b) Medium term scheduler (c) Long term scheduler
Q2. (a) Differentiate between preemptive and non-preemptive scheduling. (b) Draw the process state diagram and explain each state in detail.
Q3. (a) What is process? Explain the function of Process Control Block (PCB).
(b) Explain the concept of process scheduling and various operations on processes. (c) Differentiate between interrupt and trap.
Q4. Consider the following set of processes in order P1, P2, P3 and P4 with the length of the CPU burst time given in milliseconds. Their priorities are 3, 4, 2, and 1 respectively with 4 being the highest priority. Calculate the average waiting time and average turnaround time using following scheduling algorithms:
i. Shortest Remaining Time First ii. Round Robin (Time Quantum = 4) iii. Shortest Job First
iv. Priority Scheduling( Preemptive)
Process Arrival Time Burst Time
P1 0 9
P2 1 4
P3 2 9
P4 3 5
Q5. Assume you have certain jobs to execute with single processor:
Job Burst Time Priority
1 10 3
2 1 1
3 2 3
4 1 4
5 5 2
Q6. Consider the following set of processes in order P1, P2, P3, P4 and P5 with the length of the CPU burst time given in milliseconds. Their priorities are 3, 5, 2, 1 and 4 respectively with 5 being the highest priority. Calculate the average waiting time and average turnaround time using following scheduling algorithms:
i. Shortest Remaining Time First ii. Round Robin (Time Quantum = 2) iii. Shortest Job First
iv. Priority Scheduling( Preemptive)
Process Arrival Time Burst Time
P1 0 10
P2 1 9
P3 2 6
P4 3 7
P5 4 4
SECTION-B (MEMORY MANAGEMENT)
Q7. Explain the following with differences:
(a) Logical and physical addresses (b) Paging and segmentation
(c) Internal and external fragmentation (d) Local and Global page replacement
Q8. (a) Explain the concept of demand paging and demand segmentation. (b) Explain the concept of swapping and virtual memory.
(c) Why are segmentation and paging sometimes combined into one scheme? Justify.
Q9.Define and explain inverted page table.
Q10. (a) Consider the following segment table:
Segment Base Length
0 219 600
1 2300 14
2 90 100
3 1327 580
4 1952 96
What are the physical addresses for the following logical addresses? (i)0,430 (ii) 1,10 (iii) 2,550 (iv) 3,370 (v) 4,112
(b) What is a page fault? Explain the steps to be performed by operating system after page fault has occurred (with diagram).
to access the main memory, then find the time to access a page: (a) When the page number is in associative memory. (b) When the page number is not in associative memory. (c) Find the effective access time.
Q12. (a) Given the memory partitions of 100K, 550K, 200K, 325K and 700K (in order), how would each of the First-fit, Best-fit, and Worst-fit algorithms place processes of 450K, 112K,419K, and 215K (in order)? Which algorithm makes the most efficient use of memory?
450
112
419
215
Processes
Memory Partitions
(b) Consider the following page reference string:
1,2,3,1,4,5,6,2,1,3,2,6,4,2,3,7,6,3,4,1,2,6
How many page faults would occur for the following page replacement algorithms assuming six frames? All frames are initially empty.
(a) LRU (b) Optimal (c) FIFO
SECTION-C (File System)
Q13. What is a file? Explain the following with reference to the file. (a) Attributes and types
(b) Operations (c) Access methods
Q14. (a) Explain the distributed file system in brief.
(b) What are the problems in contiguous allocation? How are they solved by linked allocation? (c) Explain various directory structures in brief.
Q15. Suppose that disk drive has 5000 cylinders, numbered from 0 to 4999. The drive is currently at cylinder 152 and the previous request was at cylinder 125. The queue of pending request in FIFO order is: 86, 1470, 913, 1774, 1850, 850, 1525, 1728, 1000, 127
Starting from the current position, what is the total distance in cylinders that the disk arm moves to satisfy all the pending requests for each of the following disk scheduling algorithms:
(a) FCFS (b) SSTF (c) LOOK (d) C-SCAN
SECTION –C (DEADLOCKS)
Q16. (a) What is deadlock? Describe the four necessary conditions for the deadlock. Also discuss how Banker’s algorithm is used for deadlock avoidance?
(b) What is the difference between races and deadlocks? What can be done to prevent them?
Q17. Explain implementation of semaphore. State the Reader Writer problem for synchronization and explain its solution with appropriate code for both processes.
Q18. A computer system uses the banker’s algorithm to deal with deadlocks. Its current state for processes P0, P1, P2, P3 and P4 and resources A, B, C and D is shown in the table below:
Max. Need Current allocation
The current available resources: [1, 5, 2, 0]. (i) Is the system in a safe state?
(ii) If the request from process P1 arrives for (0, 4, 2, 0) can the request be granted immediately? Explain.
Q19. (a) What is wait -for graph? Obtain wait-for graph for the given resource allocation graph.
(b) What do you mean by critical section problem? Explain the requirements a solution to critical section problem must satisfy.
SECTION-D (UNIX & WINDOWS NT)
Q20. Explain the following: (a) Shell interpreter (b) Unix System call
(c) Windows NT architecture
Q21. Describe the layout of the UNIX file system. What is the structure of i-node? How does the path name get translated to i-node number?
0 0 1 2
1 7 5 0
2 3 5 6
0 6 5 2
0 6 5 6
0 0 1 2
1 0 0 0
1 3 5 4
0 6 3 2
0 0 1 4
