a) Explain the main purpose of an operating system?

b) What are the advantages of a multiprocessor system?

c) Describe the objective of multiprogramming.

d) What are necessary conditions which can lead to a deadlock situation in a system

e) State the main difference between logical from physical address space.

f) When designing the file structure for an operating system, what attributes are considered?

g) Consider an environment in which there is a one-to-one mapping between user-level threads and kernel-level threads that allows one or more threads within a process to issue blocking system calls while other threads continue to run. Explain why this model can make multithreaded program.

h) When will the page fault occur? What is the procedure for handling the page faults? Also, mention what are the steps to modify the page-fault service routine to include page replacement? (4 Marks)

i) Consider the following page reference using three frames that are initially empty. Find the page faults using FIFO algorithm,

where the page reference sequence is: 7,0,1,2,0,3,0,4,2,3,0,3,2,1,2,0,1,7,0,1 (6 Marks)

j) Assume that a task is divided into four equal-sized segments and that the system builds an eight-entry page descriptor table for each segment. Thus, the system has a combination of segmentation and paging. Assume also that the page size is 2 Kbytes.

1. What is the maximum size of each segment? (2 marks)
2. What is the maximum logical address space for the task? (2 Marks)
3. Assume that an element in physical location 00021ABC is accessed by this task. What is the format of the logical address that the task generates for it? What is the maximum physical address space for the system? (2 Marks)

k) Consider the following workload:

Process	Burst time	Priority	Arrival Time
P1	30ms	5	0
P2	60ms	1	20
P3	100ms	4	40
P4	50ms	2	60

1. Show the schedule using shortest remaining time, nonpreemptive priority (a smaller priority number implies higher priority) and round robin with quantum 30 ms. Use time scale diagram as shown below for the FCFS example to show the schedule for each requested scheduling policy. (4 Marks)

Example for FCFS (1 Unit=10 ms)

P1	P1	P1	P1	P1	P2	P2	P3	P3	P3	P3	P3	P3	P3	P3	P3	P3	P4	P4	P4	P4
0	123		4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20

2) What is the average waiting time of the above scheduling policies? (3 marks)

l) Connectivity issue is a very common definition and may encompass many problems. However, in this case, the most common definition isunexpected network failure at oneof our upstream network providers that affect the connectivity to your host server. Based on these kinds of issues, explain:

1. How can a network be certified as an effective network? What are the factors affecting them?

2) How are networks classified based on their connections?

m) Firewall which is defined as a cybersecurity tool that monitors incoming and outgoing network traffic and permits or blocks data packets based on a set of cybersecurity rules, discuss the following points related to the security and firewall components:

1. What is the difference between Stateful and Stateless Firewall?

2. What information does Stateful firewall maintains?