Introduction to Operating System (OS)

Dr P Bhaskar Naidu
M.Tech., Ph.D., PGP(NIT-W), LMISTE,LMCSI
 History of Operating System
 The First Generation (1940's to early 1950's)
 No Operating System
 All programming was done in absolute machine language, often by wiring up plug-boards to control
the machine’s basic functions.
 The Second Generation (1955-1965)
 First operating system was introduced in the early 1950's.It was called GMOS
 Created by General Motors for IBM's machine the 701.
 Single-stream batch processing systems
 The Third Generation (1965-1980)
 Introduction of multiprogramming, Unix
 Development of Minicomputer
 The Fourth Generation (1980-Present Day)
 Development of PCs
 Birth of Windows/MaC OS
2
 :Course Content
• What is an OS.
• What are its key functions.
• The evaluation of OS.
• What are the popular types of OS.
• Basics of UNIX and Windows.
• Advantages of open source OS like Linux.
• Networks OS.

3
 ?What is an Operating System
• Computer System = Hardware + Software
• Software = Application Software + System Software(OS)\
• Definition of OS:
• An Operating System is a system Software that acts like an interface in
between a user of a computer and the computer hardware components.
• Operating system goals:
 Execute user programs and make solving user problems easier
 Make the computer system convenient to use
 Use the computer hardware in an efficient manner

4
5
 The Structure of Computer Systems
 Accessing computer resources is divided into layers.
 Each layer is isolated and only interacts directly with the layer below or
above it.
 If we install a new hardware device
 No need to change anything about the user/applications.
 However, you do need to make changes to the operating system.
 You need to install the device drivers that the operating system will
use to control the new device.
 If we install a new software application
 No need to make any changes to your hardware.
 But we need to make sure the application is supported by the operating
system
 user will need to learn how to use the new application.
 If we change the operating system
 Need to make sure that both applications and hardware will compatible
6 with the new operating system.
 Computer Architecture

Special busses (roads)

ISA: Intelligent Service Architecture
connecting all input/output
PCI:Peripheral Component
devices to motherboard. Interconnect
7 USB: universal serial bus
 BUS & BRIDGES

8
 CPU – Central Processing Unit
 This is the brain of your computer.
 It performs all of the calculations.
 In order to do its job, the CPU needs commands to perform, and data to
work with.
 The instructions and data travel to and from the CPU on the system bus.
 The operating system provides rules for how that information gets back
and
forth, and how it will be used by the CPU.

9
10
 RAM – Random Access Memory
 This is like a desk, or a workspace, where your computer temporarily stores all of
the information (data) and instructions (software or program code) that it is
currently using.
 Each RAM chip contains millions of address spaces.
 Each address space is the same size, and has its own unique identifying number
(address).
 The operating system provides the rules for using these memory spaces, and
controls storage and retrieval of information from RAM.
 Device drivers for RAM chips are included with the operating system.

Problem: If RAM needs an operating system to work, and an operating system needs
RAM in order to work, how does your computer activate its RAM to load the
operating system?
11
12
 Operating System Services/Features
• . User Services
– Program Execution
– User Interface
• CLI
• GUI
– I/O Operations
• Key Board- Key Board Controller
• Mouse – Mouse Controller >>Device Controllers
• Monitor – Monitor Controller

13
 – Communication
• IPC
– File System & Manipulations
– Error Detection
• Errors- Program or H/W Components
• System Services
– Resource Allocation
– Accounting
– Protection & Security
14 • Firewalls
 A View of Operating System Services

15
 Operating System Services
• Program execution
• Control Input/output devices
• Program creation
• Error Detection and Response
• Accounting
• Security and Protection
• File Management
• Communication

16
 • Program execution
• To execute a program, several tasks need to be performed. Both the instructions and data
must be loaded into the main memory. In addition, input-output devices and files should
be initialized, and other resources must be prepared. The Operating structures handle
these kinds of tasks. The user now no longer should fear the reminiscence allocation or
multitasking or anything.
• Control Input/output devices
• As there are numerous types of I/O devices within the computer system, and each I/O
device calls for its own precise set of instructions for the operation. The Operating
System hides that info with the aid of presenting a uniform interface. Thus, it is
convenient for programmers to access such devices easily.
• Program Creation
• The Operating system offers the structures and tools, including editors and debuggers, to
17 help the programmer create, modify, and debugging programs.
 • Error Detection and Response

• An Error in a device may also cause malfunctioning of the entire device. These include hardware and
software errors such as device failure, memory error, division by zero, attempts to access forbidden
memory locations, etc. To avoid error, the operating system monitors the system for detecting errors and
takes suitable action with at least impact on running applications.

• While working with computers, errors may occur quite often. Errors may occur in the:

• Input/ Output devices: For example, connection failure in the network, lack of paper in the printer, etc.
• User program: For example: attempt to access illegal memory locations, divide by zero, use too much
CPU time, etc.
• Memory hardware: For example, Memory error, the memory becomes full, etc.
• To handle these errors and other types of possible errors, the operating system takes appropriate action
and generates messages to ensure correct and consistent computing.
18
 • Accounting

• An Operating device collects utilization records for numerous assets and tracks the
overall performance parameters and responsive time to enhance overall performance.
These personal records are beneficial for additional upgrades and tuning the device to
enhance overall performance.

• Security and Protection

• Operating device affords safety to the statistics and packages of a person and protects
any interference from unauthorized users. The safety feature counters threats, which are
published via way of individuals out of doors the manage of the running device.
19
 • For Example:

• When a user downloads something from the internet, that program may contain
malicious code that may harm the already existing programs. The operating system
ensures that proper checks are applied while downloading such programs.

• If one computer system is shared amongst a couple of users, then the various processes
must be protected from another intrusion. For this, the operating system provides
various mechanisms that allow only those processes to use resources that have gained
proper authorization from the operating system. The mechanism may include providing
unique users ids and passwords to each user.

20
 • File management
• Computers keep data and information on secondary storage devices like magnetic tape,
magnetic disk, optical disk, etc. Each storage media has its capabilities like speed,
capacity, data transfer rate, and data access methods.
• For file management, the operating system must know the types of different files and the
characteristics of different storage devices. It has to offer the proportion and safety
mechanism of documents additionally.

• Communication
• The operating system manages the exchange of data and programs among different
computers connected over a network. This communication is accomplished using
message passing and shared memory.

21
 Operating System Mode
 The User Mode is concerned with the actual
interface between the user and the system.
 It controls things like running applications
and accessing files.

 The Kernel Mode is concerned with everything

running in the background.
 It controls things like accessing system
resources, controlling hardware functions and
processing program instructions.
 System calls are used to change
22 mode from User to Kernel.
 Kernel
 Kernel is a software code that reside in central core of OS. It has complete
control over system.
 When operation system boots, kernel is first part of OS to load in main
memory.
 Kernel remains in main memory for entire duration of computer session. The
kernel code is usually loaded in to protected area of memory.
 Kernel performs it’s task like executing processes and handling interrupts in
kernel space.
 User performs it’s task in user area of memory.
 This memory separation is made in order to prevent user data and kernel
data from interfering with each other.
 Kernel does not interact directly with user, but it interacts using SHELL(Your
interface to the operating system is called a shell.) and other programs and
23
 SHELL

24
25
 …Kernel cont
 Kernel includes:-
1. Scheduler: It allocates the Kernel’s processing time to various
processes.
2. Supervisor: It grants permission to use computer system resources
to each process.
3. Interrupt handler : It handles all requests from the various
hardware devices which compete for kernel services.
4. Memory manager : allocates space in memory for all users of
kernel service.
 kernel provides services for process management, file management,
I/O management, memory management.
 System calls are used to provide these type of services.
26
 System Call
• What is a System Call

• How it works

• Types of System Calls

27
 What is a System Call
• A system call will act as a interface between s/w applications and kernel.
• System call provides the services of OS to the process via API
• When the process is being executed and if it requires any recourse , then the
process create a System call which is nothing but Interrupt and sends to the
kernel
• The Application Program Interface (API) connects the operating system's
functions to user programs. It acts as a link between the operating system
and a process, allowing user-level programs to request operating system
services.
• The kernel system can only be accessed using system calls.

28
 System Call
 Application program is just a user-process. Due to security reasons , user
applications are not given access to privileged resources(the ones controlled
by OS).
 When they need to do any I/O or have some more memory or spawn a
process or wait for signal/interrupt, it requests operating system to
facilitate all these. This request is made through System Call.
 System calls are also called software-interrupts.

29
30
 How it Works
• 1.User Space

• 2. Kernel Space

31
 Working of System Call
• 1.User Space
– Process Execution
– Process Creates one System Call
• 2.Kernal Space
– The System Call send to the Kernel Space and the System call
will be executed
– After Completing the execution the control move back to User
Space

32
 How it Works

33
34
 API – System Call – OS Relationship

35
36
37
 Types of System Calls
• There are commonly five types of system calls. These are
as follows:
1. Process Control System Call
2. File Management System Call
3. Device Management System Call
4. Information Maintenance System Call
5. Communication System Call

38
 1. Process Control System Call
•Process control is the system call that is used to direct the
processes. Some process control examples include creating, load,
abort, end, execute, process, terminate the process, etc.

2. File Management System Call

•File management is a system call that is used to handle the files.
Some file management examples include creating files, delete files,
open, close, read, write, etc.
39
 3. Device Management System Call
•Device management is a system call that is used to deal with devices. Some
examples of device management include read, device, write, get device
attributes, release device, etc.

4. Information Maintenance System Call

•Information maintenance is a system call that is used to maintain information.
There are some examples of information maintenance, including getting
system data, set time or date, get time or date, set system data, etc.

40
 5. Communication System Call
•Communication is a system call that is used for communication.
There are some examples of communication, including create, delete
communication connections, send, receive messages, etc.

41
42
 Examples of Windows and Unix system calls

43
 Standard C Library Example

44
45
 Threads
• Process: Task under execution
• Thread: light weight process
Part of process (segment)
Each Process may have multiple threads
It improves CPU utilization
Increase the performance of the application
Processer-> opening a web browser
Thread-> opening the tabs in the web browser
Example: ATM (Processor) , Services(Thread)
46
 Types of Threads
• 1. User Level Thread
• 2. Kernel level Thread

47
 User Level Thread
• 1.User Level Thread is created by the user , it is not
recognised by the os.
• 2. User Level Thread is a type of thread that is not created
using system calls
• 3. The kernel has no work in the management of user-level
threads.
.

48
 Kernel Level Thread
• 1. Kernel level thread is created by the os.
• 2. A Kernel Level Thread is a type of thread that can
recognize the Operating system easily.
• 3. The operating System Kernel helps in managing threads
• 4. Kernel helps in the management of threads

49
 User Level Thread & Kernel Level Thread

50
 Single Threaded Process

51
 Multithreaded Process

52
 Thread Models / Multithread Models
• Mapping user level threads to kernel level threads
• These Mapping process is called Thread Models.
• Kernel which are mapped to user level is called virtual
Processers

53
 • They are 3 types of Thread Models
• 1. Many-to-one Model (M:1)
• 2. one-to-one Model (1:1)
• 3. Many-to-Many Model(M:N)
– M Threads
– Create <M Kernels

54
 Many-to-one Model.1

55
 One-to-one Model .2

56
 Many-to-Many Model .3

57
 Process Management
1.Process Concept

58
59
 A stack is a data structure used by processors in operating systems to manage the
execution of programs. The stack is typically implemented in the memory of the
processor and is used to store data and return addresses during program execution .

Heaps are memory areas allocated to each program. Memory allocated to heaps can
be dynamically allocated, unlike memory allocated to stacks. As a result, the heap
segment can be requested and released whenever the program needs it. (Garbage
collector)

60
 Process State

61
 Process Scheduling

62
 PCB

63
 Scheduling Queues
 The OS maintains all Process Control Blocks (PCBs) in Process Scheduling Queues. The OS
maintains a separate queue for each of the process states and PCBs of all processes in the
same execution state are placed in the same queue. When the state of a process is changed, its
PCB is unlinked from its current queue and moved to its new state queue.

 The Operating System maintains the following important process scheduling queues −
 Job queue − This queue keeps all the processes in the system.
 Ready queue − This queue keeps a set of all processes residing in main memory, ready and
waiting to execute. A new process is always put in this queue.
 Device queues − The processes which are blocked due to unavailability of an I/O device
constitute this queue.

64
 Scheduling Queues

65
 Schedulers
 Schedulers are special system software which handle process scheduling in
various ways. Their main task is to select the jobs to be submitted into the
system and to decide which process to run. Schedulers are of three types −

 1. Long-Term Scheduler (Job Scheduler)

 2. Short-Term Scheduler (CPU Scheduler)

 3. Medium-Term Scheduler (Swapping)

66
 Swap in removes the process from hard drive(secondary
memory) & swap out removes the process from
RAM(main memory).
67
 Context Switching
• PCB
• REGISTERS
• KERNAL
• PROCESS STATE

68
 Types of Operating Systems
1. Batch Operating System
2. Multiprogramming Operating System
3. Time-Sharing OS
4. Multiprocessing OS
5. Distributed OS
6. Network OS
7. Real Time OS
8. Embedded OS
69
 Batch Operating System .1
• The users of this type of operating system does not interact with the computer directly.
• Each user prepares his job on an off-line device like punch cards and submits it to the
computer operator
• There is an operator which takes similar jobs having the same requirement and group them into
batches.
• Example : ATM MECHINE, PUNCH CARDS

70
 :Multiprogramming Operating System .2
• This type of OS is used to execute more than one jobs simultaneously by a single processor.
• It increases CPU utilization by organizing jobs so that the CPU always has one job to execute.
• Multiprogramming operating systems use the mechanism of job scheduling and CPU
scheduling.

71
 Time-Sharing Operating Systems .3
• Each task is given some time to execute so that all the tasks work smoothly.
• These systems are also known as Multi-tasking 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.

72
 Multiprocessor operating systems .4

• Multiprocessor operating systems are also known as parallel OS or

tightly coupled OS.
• Such operating systems have more than one processor in close
communication that sharing the computer bus, the clock and
sometimes memory and peripheral devices.
• It executes multiple jobs at the same time and makes the processing
faster.
• It supports large physical address space and larger virtual address
space.
• **If one processor fails then other processor should retrieve
the interrupted process state so execution of process can
continue.
73
74
 Distributed Operating System .5
• 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.
• Examples:- Locus, DYSEAC

75
 Network Operating System .6

• 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 of files, printers,
security, applications, and other networking functions over a small private
network.
• The “ other" computers arc called client computers, and each computer that
connects to a network server must be running client software designed to
request a specific service.

76
77
 Real-Time Operating System .7
• 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,
 Train, etc.

78
 Different Types of RTOS
• Deos (DDC-I)
• embOS (SEGGER)
• FreeRTOS (Amazon)
• Integrity (Green Hills Software)
• Keil RTX (ARM)
• LynxOS (Lynx Software Technologies)
• MQX (Philips NXP / Freescale)
• Nucleus (Mentor Graphics)
• Neutrino (BlackBerry)
• PikeOS (Sysgo)
• SafeRTOS (Wittenstein)
• ThreadX (Microsoft Express Logic)
• µC/OS (Micrium)
• VxWorks (Wind River)
• Zephyr (Linux Foundation)
79
80
 Embedded Operating System .8
• An embedded operating system is one that is built into the circuitry of an electronic
device.
• Embedded operating systems are now found in automobiles, bar-code scanners, cell
phones, medical equipment, and personal digital assistants.
• The most popular embedded operating systems for consumer products, such as PDAs,
include the following:
 Windows XP Embedded
 Windows CE .NET:- it supports wireless communications, multimedia and Web
browsing. It also allows for the use of smaller versions of Microsoft Word, Excel,
and Outlook.
 Palm OS:- It is the standard operating system for Palm-brand PDAs as well as
other proprietary handheld devices.
 Symbian:- OS found in “ smart” cell phones from Nokia and Sony Ericsson
81
 Popular types of OS
• Desktop Class
 Windows
 OS X
 Unix/Linux
 Chrome OS
• Server Class
 Windows Server
 Mac OS X Server
 Unix/Linux
• Mobile Class
 Android
 iOS
 Windows Phone
82
 -:Desktop Class Operating Systems
• Platform: the hardware required to run a particular operating
system
– Intel platform (IBM-compatible)
• Windows
• DOS
• UNIX
• Linux
– Macintosh platform
• Mac OS
– iPad and iPhone platform
83 • iOS
 Ms-DOS
• Single User Single Tasking OS.
• It had no built-in support for networking, and users had to manually install
drivers any time they added a new hardware component to their PC.
• DOS supports only 16-bit programs.
• Command line user interface.
• So, why is DOS still in use? Two reasons are its size and simplicity. It does
not require much memory or storage space for the system, and it docs not
require a powerful computer.

84
 Microsoft Windows
• The graphical Microsoft operating system designed for Intel-platform desktop
and notebook computers.
• Best known, greatest selection of applications available.
• Current editions include Windows 7, 8, 8.1 and 10.

85
 Mac OS
• User-friendly, runs on Mac hardware. Many applications available.
• Current editions include: Sierra, High Sierra, Mojave, Catalina & Big Sur—Version
XI(Released in Nov 2020)

86
 Linux
• Linux: An open-source, cross-platform operating system that runs on
desktops, notebooks, tablets, and smartphones.
– The name Linux is a combination Linus (the first name of
the first developer) and UNIX (another operating system.
• Users are free to modify the code, improve it, and redistribute it,
• Developers are not allowed to charge money for the Linux kernel itself
(the main part of the operating system), but they can charge money for
distributions (distros for short).

87
 Google Chrome OS
• Chrome OS. Is a popular thin client operating system.
• Thin client A computer with minimal hardware, designed for a specific task.
For example, a thin web client is designed for using the Internet.

88
 Server Operating Systems
• Windows Server
– Familiar GUI interface for those experienced with Windows
• UNIX
– Very mature server capabilities, time-tested, large user
community, stable
• Linux
– Free, customizable, many free services and utilities available

89
 Windows Server

90
 UNIX

91
 Tablet and Phone Operating Systems
• System-on-chip (SoC): An operating system that comes preinstalled on a
chip on a portable device such as a smartphone.
• Popular SoC operating systems:
 iOS: for iPad, iPhone
 Android: for a variety of tablets and phones
• Downloadable applications (apps) from an App store, for example:
 Apple App Store
 Google Play Store

92
 iOS on the iPhone and iPad
• The Apple-created operating system for Apple tablets and phones.
• The current stable version, iOS 14, was released to the public on September
16, 2020.

93
 Android
• Android, a popular OS for smartphones and tablets, is
based on Linux Kernel.
– Developed by Google
• Current versions include:
– Android 8 Oreo
– Android 9 Pie
– Android 10
– Android 11 (released on Sep, 2020)

94
 Advantage of Linux Operating System
1. Open Source
As it is open-source, its source code is easily available.
Anyone having programming knowledge can customize the operating system.
One can contribute, modify, distribute, and enhance the code for any purpose.
2. Security
The Linux security feature is the main reason that it is the most favourable option for developers.
It is not completely safe, but it is less vulnerable than others.
Each application needs to authorize by the admin user.
Linux systems do not require any antivirus program.

3. Free
Certainly, the biggest advantage of the Linux system is that it is free to use.
We can easily download it, and there is no need to buy the license for it.
It is distributed under GPL (General Public License).
Comparatively, we have to pay a huge amount for the license of the other OS
95
 Advantage of Linux Operating System
4. Lightweight
The requirements for running Linux are much less than other operating system
In Linux, the memory footprint and disk space are also lower.
Generally, most of the Linux distributions required as little as 128MB of RAM
around the same amount for disk space.
5. Stability
Linux is more stable than other operating systems.
Linux does not require to reboot the system to maintain performance levels.
It rarely hangs up or slow down. It has big up-times.

96
 Advantage of Linux Operating System
6. Performance
Linux system provides high performance over different networks.
It is capable of handling a large number of users simultaneously.
7. Flexibility
Linux operating system is very flexible.
It can be used for desktop applications, embedded systems, and server applications too.
It also provides various restriction options for specific computers.
We can install only necessary components for a system.
8. Software Updates
In Linux, the software updates are in user control.
We can select the required updates.
There a large number of system updates are available.
These updates are much faster than other operating systems.
So, the system updates can be installed easily without facing any issue.
97
 Advantage of Linux Operating System
9. Distributions/ Distros
There are many Linux distributions available in the market.
It provides various options and flavors of Linux to the users.
We can choose any distros according to our needs.
Some popular distros are Ubuntu, Fedora, Debian, Linux Mint, Arch Linux,
For the beginners, Ubuntu and Linux Mint would be useful.
Debian and Fedora would be good choices for proficient programmers.
10. Live CD/USB
Almost all Linux distributions have a Live CD/USB option.
It allows us to try or run the Linux operating system without installing it.
11. Graphical User Interface
Linux is a command-line based OS but it provides an interactive user interface like Windows.
98
 Advantage of Linux Operating System
12. Suitable for programmers
It supports almost all of the most used programming languages such as C/C++, Java, Python, Ruby,
and more.
Further, it offers a vast range of useful applications for development.
The programmers prefer the Linux terminal over the Windows command line.
The package manager on Linux system helps programmers to understand how things are done.
Bash scripting is also a functional feature for the programmers.
It also provides support for SSH, which helps in managing the servers quickly.
13. Community Support
Linux provides large community support.
We can find support from various sources.
There are many forums available on the web to assist users.
Further, developers from the various open source communities are ready to help us.
99
 Advantage of Linux Operating System
14. Privacy
Linux always takes care of user privacy as it never takes much private data from the user.
Comparatively, other operating systems ask for the user's private data.
15. Networking
Linux facilitates with powerful support for networking. The client-server systems can be easily set
to a Linux system. It provides various command-line tools such as ssh, ip, mail, telnet, and more
for connectivity with the other systems and servers. Tasks such as network backup are much
faster than others.
16. Compatibility
Linux is compatible with a large number of file formats as it supports almost all file formats.
17. Installation
Linux installation process takes less time than other operating systems such as Windows. Further,
its installation process is much easy as it requires less user input. It does not require much more
system configuration even it can be easily installed on old machines having less configuration.
10
 Advantage of Linux Operating System
18. Multiple Desktop Support
Linux system provides multiple desktop environment support for its enhanced use. The desktop
environment option can be selected during installation. We can select any desktop environment
such as GNOME (GNU Network Object Model Environment) or KDE (K Desktop
Environment) as both have their specific environment.
19. Multitasking
It is a multitasking operating system as it can run multiple tasks simultaneously without affecting
the system speed.
20. Heavily Documented for beginners
There are many command-line options that provide documentation on commands, libraries,
standards such as manual pages and info pages. Also, there are plenty of documents available on
the internet in different formats, such as Linux tutorials, Linux documentation project,
Serverfault, and more. To help the beginners, several communities are available such as Ask
Ubuntu, Reddit, and StackOverflow.
10
 UNIX Shell and Utilities

User
The shell used to be in the
kernel but now is a utility outside Utilities Shell
of it.
Easy to change/debug.
Kernel
Many of them (sh, bsh, csh,
ksh, tcsh, wsh, bash)
Possible to switch between Hardware
10 them (chsh)
 A very simplified Shell

10
10