Operating System

An Operating System performs all the basic tasks like managing files, processes,
and memory. Thus operating system acts as the manager of all the resources,
i.e. resource manager. Thus, the operating system becomes an interface between
the user and the machine. It is one of the most required software that is present in
the device.
Operating System is a type of software that works as an interface between the
system program and the hardware.

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 requirement and groups
them into batches. It is the responsibility of the operator to sort jobs with similar
needs.

Batch Operating System

Advantages of Batch Operating System

• It is very difficult to guess or know the time required for any job to
complete. Processors of the batch systems know how long the job would
be when it is in the queue.
• Multiple users can share the batch systems.
• The idle time for the batch system is very less.
• It is easy to manage large work repeatedly in batch systems.
Disadvantages of Batch Operating System
 •The computer operators should be well known with batch systems.
• Batch systems are hard to debug.
• It is sometimes costly.
• The other jobs will have to wait for an unknown time if any job fails.
Examples of Batch Operating Systems: Payroll Systems, Bank Statements, etc.

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 execution of resources.

MultiProgramming
Advantages of Multi-Programming Operating System
• Multi Programming increases the Throughput of the System.
• It helps in reducing the response time.
Disadvantages of Multi-Programming Operating System
• There is not any facility for user interaction of system resources with the
system.

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.
 Multiprocessing
Advantages of Multi-Processing Operating System
• It increases the throughput of the system.
• As it has several processors, so, if one processor fails, we can proceed
with another processor.
Disadvantages of Multi-Processing Operating System
• Due to the multiple CPU, it can be more complex and somehow difficult
to understand.

4. Multi-Tasking Operating System

Multitasking Operating System is simply a multiprogramming Operating System

with having facility of a Round-Robin Scheduling Algorithm. It can run multiple
programs simultaneously.

Multitasking
Advantages of Multi-Tasking Operating System
• Multiple Programs can be executed simultaneously in Multi-Tasking
Operating System.
• It comes with proper memory management.
Disadvantages of Multi-Tasking Operating System
• The system gets heated in case of heavy programs multiple times.

5. Time-Sharing Operating Systems

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.

Time-Sharing OS

Advantages of Time-Sharing OS
• Each task gets an equal opportunity.
• Fewer chances of duplication of software.
• CPU idle time can be reduced.
• Resource Sharing: Time-sharing systems allow multiple users to share
hardware resources such as the CPU, memory, and peripherals, reducing
the cost of hardware and increasing efficiency.
• Improved Productivity: Time-sharing allows users to work concurrently,
thereby reducing the waiting time for their turn to use the computer. This
increased productivity translates to more work getting done in less time.
 • Improved User Experience: Time-sharing provides an interactive
environment that allows users to communicate with the computer in real
time, providing a better user experience than batch processing.
Disadvantages of Time-Sharing OS
• Reliability problem.
• One must have to take care of the security and integrity of user programs
and data.
• Data communication problem.
• High Overhead: Time-sharing systems have a higher overhead than
other operating systems due to the need for scheduling, context
switching, and other overheads that come with supporting multiple
users.
• Complexity: Time-sharing systems are complex and require advanced
software to manage multiple users simultaneously. This complexity
increases the chance of bugs and errors.
• Security Risks: With multiple users sharing resources, the risk of security
breaches increases. Time-sharing systems require careful management
of user access, authentication, and authorization to ensure the security of
data and software.
Examples of Time-Sharing OS with explanation
• IBM VM/CMS: IBM VM/CMS is a time-sharing operating system that was
first introduced in 1972. It is still in use today, providing a virtual
machine environment that allows multiple users to run their own
instances of operating systems and applications.
• TSO (Time Sharing Option): TSO is a time-sharing operating system
that was first introduced in the 1960s by IBM for the IBM System/360
mainframe computer. It allowed multiple users to access the same
computer simultaneously, running their own applications.
• Windows Terminal Services: Windows Terminal Services is a time-
sharing operating system that allows multiple users to access a
Windows server remotely. Users can run their own applications and
access shared resources, such as printers and network storage, in real-
time.

6. 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. The major benefit of working with these types of the operating system is
that it is always possible that one user can access the files or software which are
not actually present on his system but some other system connected within this
network i.e., remote access is enabled within the devices connected in that
network.

Distributed OS

Advantages of Distributed Operating System

• Failure of one will not affect the other network communication, as all
systems are independent of each other.
• Electronic mail increases the data exchange speed.
• Since resources are being shared, computation is highly fast and durable.
• Load on host computer reduces.
• These systems are easily scalable as many systems can be easily added
to the network.
• Delay in data processing reduces.
Disadvantages of Distributed Operating System
• Failure of the main network will stop the entire communication.
• To establish distributed systems the language is used not well-defined
yet.
• These types of systems are not readily available as they are very
expensive. Not only that the underlying software is highly complex and
not understood well yet.
Examples of Distributed Operating Systems are LOCUS, etc.

7. 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.

Network Operating System

Advantages of Network Operating System

• Highly stable centralized servers.
• Security concerns are handled through servers.
• New technologies and hardware up-gradation are easily integrated into
the system.
• Server access is possible remotely from different locations and types of
systems.
Disadvantages of Network Operating System
• Servers are costly.
• User has to depend on a central location for most operations.
• Maintenance and updates are required regularly.
Examples of Network Operating Systems are Microsoft Windows Server 2003,
Microsoft Windows Server 2008, UNIX, Linux, Mac OS X, Novell NetWare, BSD,
etc.
8. 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.
Types of Real-Time Operating Systems
• Hard Real-Time Systems:
Hard Real-Time OSs are meant for applications where time constraints
are very strict and even the shortest possible delay is not acceptable.
These systems are built for saving life like automatic parachutes or
airbags which are required to be readily available in case of an accident.
Virtual memory is rarely found in these systems.
• Soft Real-Time Systems:
These OSs are for applications where time-constraint is less strict.

Real-Time Operating System

Advantages of RTOS
• Maximum Consumption: Maximum utilization of devices and systems,
thus more output from all the resources.
• Task Shifting: The time assigned for shifting tasks in these systems is
very less. For example, in older systems, it takes about 10 microseconds
in shifting from one task to another, and in the latest systems, it takes 3
microseconds.
• Focus on Application: Focus on running applications and less
importance on applications that are in the queue.
 • Real-time operating system in the embedded system: Since the size of
programs is small, RTOS can also be used in embedded systems like in
transport and others.
• Error Free: These types of systems are error-free.
• Memory Allocation: Memory allocation is best managed in these types
of systems.
Disadvantages of RTOS
• Limited Tasks: Very few tasks run at the same time and their
concentration is very less on a few applications to avoid errors.
• Use heavy system resources: Sometimes the system resources are not
so good and they are expensive as well.
• Complex Algorithms: The algorithms are very complex and difficult for
the designer to write on.
• Device driver and interrupt signals: It needs specific device drivers and
interrupts signal to respond earliest to interrupts.
• Thread Priority: It is not good to set thread priority as these systems are
very less prone to switching tasks.
Examples of Real-Time Operating Systems are Scientific experiments, medical
imaging systems, industrial control systems, weapon systems, robots, air traffic
control systems, etc.

Difference between Multiprogramming,

multitasking, multithreading and
multiprocessing

1. Multiprogramming – Multiprogramming is known as keeping multiple

programs in the main memory at the same time ready for execution.
2. Multiprocessing – A computer using more than one CPU at a time.
3. Multitasking – Multitasking is nothing but multiprogramming with a
Round-robin scheduling algorithm.
4. Multithreading is an extension of multitasking.
 Feature Multiprogramming Multitasking Multithreading Multiprocessing

Running Running
Running multiple
Running multiple multiple tasks multiple threads
processes on
Definition programs on a (applications) within a single
multiple CPUs
single CPU on a single task
(or cores)
CPU (application)

Resources
Resources (CPU, Each process has
Resources (CPU, (CPU,
Resource memory) are its own set of
memory) are shared memory) are
Sharing shared among resources (CPU,
among programs shared among
threads memory)
tasks

Uses priority- Uses priority-

Uses round-robin or
based or time- based or time- Each process can
priority-based
slicing slicing have its own
Scheduling scheduling to
scheduling to scheduling to scheduling
allocate CPU time to
allocate CPU allocate CPU algorithm
programs
time to tasks time to threads

Each program has Each task has Threads share Each process has
Memory
its own memory its own memory space its own memory
Management
space memory space within a task space

Requires a
Requires a Requires a
Requires a context context switch
Context context switch context switch to
switch to switch to switch
Switching to switch switch between
between programs between
between tasks processes
threads

Uses thread Uses inter-

Uses message
synchronization process
Inter-Process Uses message passing or
mechanisms communication
Communication passing or shared shared
(e.g., locks, mechanisms (e.g.,
(IPC) memory for IPC memory for
semaphores) for pipes, sockets)
IPC
IPC for IPC
Why are Operating Systems Used?
Operating System is used as a communication channel between the Computer
hardware and the user. It works as an intermediate between System Hardware
and End-User. Operating System handles the following responsibilities:
• It controls all the computer resources.
• It provides valuable services to user programs.
• It coordinates the execution of user programs.
• It provides resources for user programs.
• It provides an interface (virtual machine) to the user.
• It hides the complexity of software.
• It supports multiple execution modes.
• It monitors the execution of user programs to prevent errors.

Functions of an Operating System

Memory Management
The operating system manages the Primary Memory or Main Memory. Main
memory is made up of a large array of bytes or words where each byte or word is
assigned a certain address. Main memory is fast storage and it can be accessed
directly by the CPU. For a program to be executed, it should be first loaded in the
main memory. An operating system manages the allocation and deallocation of
memory to various processes and ensures that the other process does not
consume the memory allocated to one process. It keeps track of primary memory,
i.e., which bytes of memory are used by which user program. The memory
addresses that have already been allocated and the memory addresses of the
memory that has not yet been used.
• In multiprogramming, the OS decides the order in which processes are
granted memory access, and for how long.
• It Allocates the memory to a process when the process requests it and
deallocates the memory when the process has terminated or is
performing an I/O operation.

Memory Management
Processor Management
In a multi-programming environment, the OS decides the order in which processes
have access to the processor, and how much processing time each process has.
This function of OS is called Process Scheduling. An Operating System performs
the following activities for Processor Management.
An operating system manages the processor’s work by allocating various jobs to it
and ensuring that each process receives enough time from the processor to
function properly.
Keeps track of the status of processes. The program which performs this task is
known as a traffic controller. Allocates the CPU that is a processor to a process.
De-allocates processor when a process is no longer required.

Processor Management

Device Management
An OS manages device communication via its respective drivers. It performs the
following activities for device management. Keeps track of all devices connected
to the system. designates a program responsible for every device known as the
Input/Output controller. Decide which process gets access to a certain device and
for how long. Allocates devices effectively and efficiently. Deallocates devices
when they are no longer required. There are various input and output devices. an
OS controls the working of these input-output devices. It receives the requests
from these devices, performs a specific task, and communicates back to the
requesting process.
File Management
A file system is organized into directories for efficient or easy navigation and
usage. These directories may contain other directories and other files. An
Operating System carries out the following file management activities. It keeps
track of where information is stored, user access settings, the status of every file,
and more. These facilities are collectively known as the file system. An OS keeps
track of information regarding the creation, deletion, transfer, copy, and storage of
files in an organized way. It also maintains the integrity of the data stored in these
files, including the file directory structure, by protecting against unauthorized
access.

File Management

User Interface or Command Interpreter

The user interacts with the computer system through the operating system. Hence
OS acts as an interface between the user and the computer hardware. This user
interface is offered through a set of commands or a graphical user interface (GUI).
Through this interface, the user makes interacts with the applications and the
machine hardware.

Command Interpreter

Booting the Computer

The process of starting or restarting the computer is known as booting. If the
computer is switched off completely and if turned on then it is called cold booting.
Warm booting is a process of using the operating system to restart the computer.
Security
The operating system uses password protection to protect user data and similar
other techniques. it also prevents unauthorized access to programs and user
data. The operating system provides various techniques which assure the integrity
and confidentiality of user data. The following security measures are used to
protect user data:
• Protection against unauthorized access through login.
• Protection against intrusion by keeping the firewall active.
• Protecting the system memory against malicious access.
• Displaying messages related to system vulnerabilities.
Control Over System Performance
Operating systems play a pivotal role in controlling and optimizing system
performance. They act as intermediaries between hardware and software,
ensuring that computing resources are efficiently utilized. One fundamental
aspect is resource allocation, where the OS allocates CPU time, memory, and I/O
devices to different processes, striving to provide fair and optimal resource
utilization. Process scheduling, a critical function, helps decide which processes or
threads should run when preventing any single task from monopolizing the CPU
and enabling effective multitasking.

Control Over System Performance

Job Accounting
The operating system Keeps track of time and resources used by various tasks
and users, this information can be used to track resource usage for a particular
user or group of users. In a multitasking OS where multiple programs run
simultaneously, the OS determines which applications should run in which order
and how time should be allocated to each application.
Error-Detecting Aids
The operating system constantly monitors the system to detect errors and avoid
malfunctioning computer systems. From time to time, the operating system checks
the system for any external threat or malicious software activity. It also checks the
hardware for any type of damage. This process displays several alerts to the user
so that the appropriate action can be taken against any damage caused to the
system.
Coordination Between Other Software and Users
Operating systems also coordinate and assign interpreters, compilers, assemblers,
and other software to the various users of the computer systems. In simpler
terms, think of the operating system as the traffic cop of your computer. It directs
and manages how different software programs can share your computer’s
resources without causing chaos. It ensures that when you want to use a program,
it runs smoothly without crashing or causing problems for others. So, it’s like the
friendly officer ensuring a smooth flow of traffic on a busy road, making sure
everyone gets where they need to go without any accidents or jams.
Performs Basic Computer Tasks
The management of various peripheral devices such as the mouse, keyboard, and
printer is carried out by the operating system. Today most operating systems are
plug-and-play. These operating systems automatically recognize and configure
the devices with no user interference.
Network Management
• Network Communication: Think of them as traffic cops for your internet
traffic. Operating systems help computers talk to each other and the
internet. They manage how data is packaged and sent over the network,
making sure it arrives safely and in the right order.
• Settings and Monitoring: Think of them as the settings and security
guard for your internet connection. They also let you set up your network
connections, like Wi-Fi or Ethernet, and keep an eye on how your
network is doing. They make sure your computer is using the network
efficiently and securely, like adjusting the speed of your internet or
protecting your computer from online threats.
Services Provided by an Operating System
The Operating System provides certain services to the users which can be listed in
the following manner:
• User Interface: Almost all operating systems have a user interface (UI).
This interface can take several forms. One is a command-line
interface(CLI), which uses text commands and a method for entering
them (say, a keyboard for typing in commands in a specific format with
specific options). Another is a batch interface, in which commands and
directives to control those commands are entered into files, and those
files are executed. Most commonly, a graphical user interface (GUI) is
used. the interface is a window system with a pointing device to direct
I/O, choose from menus, and make selections and a keyboard to enter
text.
• Program Execution: The Operating System is responsible for the
execution of all types of programs whether it be user programs or
system programs. The Operating System utilizes various resources
available for the efficient running of all types of functionalities.
• Handling Input/Output Operations: The Operating System is
responsible for handling all sorts of inputs, i.e., from the keyboard,
mouse, desktop, etc. The Operating System does all interfacing most
appropriately regarding all kinds of Inputs and Outputs.
For example, there is a difference between all types of peripheral devices
such as mice or keyboards, the Operating System is responsible for
handling data between them.
• Manipulation of File System: The Operating System is responsible for
making decisions regarding the storage of all types of data or files,
i.e., floppy disk/hard disk/pen drive, etc. The Operating System decides
how the data should be manipulated and stored.
• Resource Allocation: The Operating System ensures the proper use of
all the resources available by deciding which resource to be used by
whom for how much time. All the decisions are taken by the Operating
System.
• Accounting: The Operating System tracks an account of all the
functionalities taking place in the computer system at a time. All the
details such as the types of errors that occurred are recorded by the
Operating System.
• Information and Resource Protection: The Operating System is
responsible for using all the information and resources available on the
machine in the most protected way. The Operating System must foil an
 attempt from any external resource to hamper any sort of data or
information.
• Communication: The operating system implements communication
between one process to another process to exchange information. Such
communication may occur between processes that are executing on the
same computer or between processes that are executing on different
computer systems tied together by a computer network.
• System Services: The operating system provides various system
services, such as printing, time and date management, and event
logging.
• Error Detection: The operating system needs to be detecting and
correcting errors constantly. Errors may occur in the CPU and memory
hardware ( for eg. a memory error or a power failure), in I/O devices (such
as a parity error on disk, a connection failure on a network, or a lack of
paper in the printer), and in the user program ( an arithmetic overflow, an
attempt to access an illegal memory location or a too-great use of CPU
time). For each type of error, the operating system should take the
appropriate action to ensure correct and consistent computing.
 Operating System Evolution/ History

The history of the operating system has four generations now. The evolution of the
Operating system can be understood from the following image.

First Generation

(1945-1955) In this generation, operating systems were not introduced therefore

the instruction was directly given to the computer systems. All the code was
included to communicate with the connected hardware and the system.

Electronic computers were introduced during the 1940s when there were no
operating systems therefore the code was written in machine language where they
were just used to solve simple mathematic problems.

Example - to control the machine functions plug boards were used using the
wiring.

Second Generation

(1955-1965) GMOS (General Motos operating system) was the first operating
system that came into the picture in the 1950s which was developed for IBM
computers. IBM was the first one that bought an operating system into the world.
In the second generation, around the 1960s the first UNIX Operating system was
developed that was available for free for a few years. Also, the batch processing
system, where all the similar jobs are collected in groups by the system, and then
all the jobs are submitted to the operating system using a punch card to execute all
jobs in a machine.

Example - Type of operating system and Batch OS.

Third Generation

(1965-1980) In the third generation, the concept of multiprogramming was

introduced in which multiple tasks could be performed in a single computer i.e.,
operating system. Due to performing multiple tasks at a time, multiprogramming
allows the CPU to be busy every time multiple tasks are performed on the same
computer. With the DEC PDP-1 in 1961, the development of minicomputers'
phenomenal growth was introduced.

Example - Concept of multiprogramming and types of operating systems used in

multiprogramming.

Fourth Generation

(1980-now) The evolution of computers aka operating systems came under the
fourth generation. Every user is using their personal computers in this generation.
The concept of personal computers is similar to the minicomputer that was
introduced in the third generation. The birth of the Microsoft Windows operating
system was in 1975 and then Bill Gates took the personal computers to next level
by launching MS-DOS in 1981, but due to the cryptic commands, it was difficult for
a user to get hold of the commands. In this generation, people were also introduced
to Graphic User Interface(GUI). Today, Windows is the most popular operating
system and has evolved from Windows 95, Windows 98, Windows XP, and
Windows 7. The most used Windows operating system was Windows 7
and Windows 10. In 2021, Windows 11 was introduced with major changes. Apple
also introduced its operating system known as MacOS which is also as popular as
Windows these days.