Full Marks: 60
Pass Marks: 24
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.

Section A (2×10=20)

Attempt any two questions:

1. Define the essential properties of the following types of operating systems:

   • a) Batch
   • b) Interactive
   • c) Time Sharing
   • d) Real Time
   • e) Handheld

   OR

   Why do some processes require high priority? What would happen if all processes have the same priority? Mention the merits and demerits of assigning priority on a process.

2. Given references to the following pages by a program:

   0, 9, 0, 1, 8, 1, 8, 7, 8, 7, 1, 2, 8, 2, 7, 8, 2, 3, 8, 3

   How many page faults will occur if the program has three page frames for each of the following algorithms?

   • a) FIFO
   • b) Optimal
   • c) Second Chance
   • d) LRU

3. For the processes listed in the following table, draw a Gantt chart illustrating their execution and calculate the average waiting time using:

   • a) First-Come-First-Serve (FCFS)
   • b) Shortest-Job-First (SJF)
   • c) Shortest-Remaining-Time-Next (SRTN)
   • d) Round-Robin (quantum = 2)
   • e) Round-Robin (quantum = 1)

   Process	Arrival Time	Burst Time
   A	0.00	4
   B	2.01	7
   C	3.01	2
   D	3.02	2

Section B (8×5=40)

Attempt any eight questions:

4. Explain Peterson’s concept for the solution of the critical section problem.
5. Show how the sleep and wakeup solution is better than the busy waiting solution for the critical section problem.
6. Describe how multithreading improves performance over a single-threaded solution.
7. Explain how priority scheduling works. In how many ways can priority be assigned?
8. What do you mean by deadlock prevention? Mention the mechanism for deadlock prevention.
9. Two separate systems, one implemented in bitmap and another in a linked list, manage the fragmentation of 256 MB memory. For bitmap, allocation units are 512 bytes. For the linked list, each hole or segment is 32KB, and each node in the list needs 32 bits. How many bytes of storage are required for each method? Which one is better in terms of memory space required?
10. Distinguish between paging and segmentation. Why do many systems use the combination of both?
11. Compare bitmap and linked list implementation of disk free-space management. How much space is required in memory to store a bitmap for a 20GB hard disk with a 2KB block size?
12. How does DMA (Direct Memory Access) increase system concurrency? How does it complicate the hardware design?