Q 1.

Operating System with its types -

An operating system acts as an intermediary between the user of a computer and

computer hardware. In short its an interface between computer hardware and
user.

• The purpose of an operating system is to provide an environment in which a

user can execute programs conveniently and efficiently.

• An operating system is software that manages computer hardware and

software. The hardware must provide appropriate mechanisms to ensure the
correct operation of the computer system and to prevent user programs from
interfering with the proper operation of the system.

• Operating system is a program running at all times on the computer (usually

called the kernel), with all else being application.

Types of Operating Systems -

1. Batch Operating System

This type of operating system does not interact with the computer directly. There
is an operator which takes similar jobs having the same requirements and groups
them into batches. It is the responsibility of the operator to sort jobs with similar
needs. Batch Operating System is designed to manage and execute a large number
of jobs efficiently by processing them in groups.

2. Multi-Programming Operating System

Multiprogramming Operating Systems can be simply illustrated as more than one

program is present in the main memory and any one of them can be kept in
execution. This is basically used for better utilization of resources.

(i) Time-Sharing Operating Systems -

It is a type of Multiprogramming system with every process running in round robin
manner. Each task is given some time to execute so that all the tasks work
smoothly. Each user gets the time of the CPU as they use a single system. These
systems are also known as Multitasking Systems. The task can be from a single
user or different users also. The time that each task gets to execute is called
quantum. After this time interval is over OS switches over to the next task.

(ii) Multitasking -
Time Sharing and Multiprogramming systems are also called multitasking
sometimes as multiple tasks run in interleaving manner.

3. Multi-Processing Operating System -

Multi-Processing Operating System is a type of Operating System in which more
than one CPU is used for the execution of resources. It betters the throughput of
the System.

4. Multi User Operating Systems -

These systems allow multiple users to be active at the same time. These system
can be either multiprocessor or single processor with interleaving.

5. Distributed Operating System -

These types of operating system is a recent advancement in the world of
computer technology and are being widely accepted all over the world and, that
too, at a great pace. Various autonomous interconnected computers communicate
with each other using a shared communication network. Independent systems
possess their own memory unit and CPU. These are referred to as loosely coupled
systems or distributed systems . These systems’ processors differ in size and
function.

6. Network Operating System -

These systems run on a server and provide the capability to manage data, users,
groups, security, applications, and other networking functions. These types of
operating systems allow shared access to files, printers, security, applications, and
other networking functions over a small private network. One more important
aspect of Network Operating Systems is that all the users are well aware of the
underlying configuration, of all other users within the network, their individual
connections, etc. and that’s why these computers are popularly known as tightly
coupled systems .

7. Real-Time Operating System -

These types of OSs serve real-time systems. The time interval required to process
and respond to inputs is very small. This time interval is called response time.
Real-time systems are used when there are time requirements that are very strict
like missile systems, air traffic control systems, robots, etc.

Q4.
CPU scheduling with algorithms -
CPU scheduling is a process used by the operating system to decide which task or
process gets to use the CPU at a particular time. This is important because a CPU
can only handle one task at a time, but there are usually many tasks that need to
be processed. The following are different purposes of a CPU scheduling time.

• Maximize the CPU utilization

• Minimize the response and waiting time of the process.

1. First Come, First Serve (FCFS) -

First Come, First Serve (FCFS) is one of the simplest types of CPU scheduling
algorithms. It is exactly what it sounds like: processes are attended to in the order
in which they arrive in the ready queue, much like customers lining up at a grocery
store.

FCFS Scheduling is a non-preemptive algorithm, meaning once a process starts

running, it cannot be stopped until it voluntarily relinquishes the CPU, typically
when it terminates or performs I/O. This method schedules processes in the order
they arrive, without considering priority or other factors.

2. Shortest Job First (SJF) -

Shortest Job First (SJF) or Shortest Job Next (SJN) is a scheduling process that
selects the waiting process with the smallest execution time to execute next. This
scheduling method may or may not be preemptive. Significantly reduces the
average waiting time for other processes waiting to be executed.

3. Shortest Remaining Time First (SRTF) -

Shortest Remaining Time First (SRTF). In SRTF, the process with the least time left
to finish is selected to run. The running process will continue until it finishes or a
new process with a shorter remaining time arrives. This way, the process that can
finish the fastest is always given priority.

4. Round Robin -
Round Robin Scheduling is a method used by operating systems to manage the
execution time of multiple processes that are competing for CPU attention. It is
called "round robin" because the system rotates through all the processes,
allocating each of them a fixed time slice or "quantum", regardless of their
priority.

The primary goal of this scheduling method is to ensure that all processes are
given an equal opportunity to execute, promoting fairness among tasks.

5. Priority scheduling -
Priority scheduling is one of the most common scheduling algorithms used by the
operating system to schedule processes based on their priority. Each process is
assigned a priority value based on criteria such as memory requirements, time
requirements, other resource needs, or the ratio of average I/O to average CPU
burst time.
The process with the highest priority is selected for execution first. If there are
multiple processes sharing the same priority, they are scheduled in the order they
arrived, following a First-Come, First-Served approach. The chosen process is then
executed, either until completion or until it is preempted, depending on whether
the scheduling is preemptive or non-preemptive.

Priority Scheduling can be implemented in two ways:

(i)Non-Preemptive Priority Scheduling
(ii)Preemptive Priority Scheduling
6.Highest Response Ratio Next (HRRN) -
CPU scheduling is the process of deciding which process will own the CPU to use
while another process is suspended. The main function of CPU scheduling is to
ensure that whenever the CPU remains idle, the OS has at least selected one of
the processes available in the ready-to-use line. Highest Response Ratio Next
(HRRN) Scheduling is a part of non-preemptive CPU scheduling.

Q 5.
Swapping -
When a process is executed it must have resided in memory. Swapping is a
process of swapping a process temporarily into a secondary memory from the
main memory, which is fast compared to secondary memory. A swapping allows
more processes to be run and can be fit into memory at one time. The main part
of swapping is transferred time and the total time is directly proportional to the
amount of memory swapped. Swapping is also known as roll-out, or roll because if
a higher priority process arrives and wants service, the memory manager can
swap out the lower priority process and then load and execute the higher priority
process. After finishing higher priority work, the lower priority process swapped
back in memory and continued to the execution process.

Swapping in an operating system is a process that moves data or programs

between the computer's main memory (RAM) and a secondary storage (usually a
hard disk or SSD). This helps manage the limited space in RAM and allows the
system to run more programs than it could otherwise handle simultaneously.It's
important to remember that swapping is only used when data isn't available in
RAM. Although the swapping process degrades system performance, it allows
larger and multiple processes to run concurrently. Because of this, swapping is
also known as memory compaction. The CPU scheduler determines which
processes are swapped in and which are swapped out. Consider a
multiprogramming environment that employs a priority-based scheduling
algorithm.

Q 7.
What is a Distributed File System (DFS)?
A Distributed File System (DFS) is a file system that is distributed on multiple file
servers or multiple locations. It makes the programs to access or to store isolated
files with the local ones, allowing programmers to access files from any network
or computer. It manages files and folders on different computers. It is mainly
designed to provide file storage and access controlled to files over LAN and WAN.

A DFS is also called a client-server architecture based application, which allows the
user or clients to access the data from the server as it is stored in their own
computer. It provides location transparency and redundancy help to improve the
data availability. And also use data replication strategy on multiple servers to
prevent data access failure.

Benefits -
The benefits of DFS are as follows −
• Flexibility in storage management − In DFS, storage management is very flexible
and we can easily modify it according to our need.

• Load sharing advantage − Load sharing can be done with optimal results using
the DFS. Load sharing is one of the best benefits of DFS.

• Security Integration − If we want to implement security then it can be easily

done in the DFS.

• Graphical way of Administration − Graphical view of administration window is

available here, which reduces cost in administration training.

• High Availability − High availability is also one of the best benefits of DFS. It
keeps all the important data available all the time.