Unix-Linux Operating Systems and its concepts

Darshan Institute of Engineering &
Technology, Rajkot
Unit - 9
Unix/Linux
Operating
System
maulik.trivedi@darshan.ac.in
9998 265 805
Computer Engineering Department
Prof. Maulik D. Trivedi
Operating System (OS)
GTU # 3140702

✓ Loopin
g
Outline
• What is an Operating System (OS) ?
• Tasks of Operating System
• What is Unix?
• Unix Operating System
• Unix History
• Features of Unix
• What is shell?
• Linux Operating System
• Architecture
• Component of Linux System
• Basic Function of Kernel
• Directory Structure
• Linux Vs. Windows

What is an Operating
System?
Section - 1

Prof. Maulik D Trivedi
#3140702 (OS) ⬥ Unit 9 – Unix/Linux Operating
4
Operating System
🞂 An operating system, or "OS," is software that communicates with the hardware
and allows other programs to run.
🞂 Every desktop computer, tablet, and smartphone includes an operating
system that provides basic functionality for the device.
🞂 Common desktop operating systems include Windows, Mac OS, and Linux and
mobile operating system includes android and iOS.
🞂 It manages all the available resources on a computer, from the CPU, to memory,
to hard disk accesses.
🞂 In simple terms, an operating system is a manager.

5
Tasks of Operating System
Recognizes and install peripherals devices
Allows software to communicate with
hardware
Manages file and folders
Manage system security
Move data to and from the hard disk
Install and run other software
applications
Handles system errors and alert user
1
2
3
4
5
6
7

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What is OS?

7
What is UNIX ?
🞂 Unix is a portable, multitasking, multiuser, time-sharing operating system (OS)
originally developed by AT&T Bell Labs.
🞂 Several people can use a UNIX computer at the same time; hence UNIX is called
a multiuser system.
🞂 Any of these users can also run multiple programs at the same time; hence
UNIX is called multitasking.
🞂 There are many different versions of UNIX, although they share common
similarities.
🞂 The most popular varieties of UNIX are Sun Solaris, GNU/Linux, and MacOS X.

8
The UNIX Operating System
🞂 The UNIX operating system is made up of three
parts.
1. Kernel
2. Shell
3. Application
🞂 The kernel is that part of the system which
manages the resources of whatever computer
system it lives on.
🞂 The shell is the command interpreter.
🞂 The shell listens to your terminal and translates
your requests into actions on the part of the
kernel and the many utility programs.
🞂 The Applications which execute on the shell. It
can be any utility program like a web browser,
video player, etc.
🞂 The file system is the organizing structure for

9
What exactly is a “shell”?
🞂 The shell acts as an interface between the user and the kernel.
🞂 The shell is a command line interpreter (CLI).
🞂 User commands are often entered on a command line interface that is provided
by a ‘shell’.
🞂 The shell is a program that reads the user commands, evaluates it, and then
prints the result.
🞂 For evaluating the command, the shell may execute other commands, or pass
them to the ‘kernel’.
🞂 The most popular shells are: bash, tcsh, csh, and korn.
🞂 Shell commands are CASE SENSITIVE.

10
Operating System Organization

11
Unix History
• The UNIX operating system was born in the late 1960s.
• It originally began as a one-man project led by Ken Thompson of Bell Labs.
• In the time since UNIX was first developed, it has gone through many different
generations.
• Some differ substantially from the original version, like Berkeley Software
Distribution (BSD) or Linux.
• Others, still contain major portions that are based on the original source code.

12
The Features of the Unix
🞂 Open Source
🞂 Open-source software is a type of computer
software in which source code is released
under a license.
🞂 In which, the copyright holder grants users
the rights to use, study, change, and
distribute the software to anyone and for
any purpose.
🞂 Open-source software may develop in a
collaborative public manner.
🞂 Linux source code is freely available, and it
is community-based development project.

13
The Features of the Unix – Cont.
🞂 Multiuser capability
🞂 Multi-user is a term that defines an
operating system, computer program, or a
game that allows use by more than
one users of the same computer at the
same time.
🞂 An example is a Unix server
where multiple remote users have access to
the Unix shell prompt at the same time.
🞂 All the terminals are connected to the main
computer whose resources are available by
all users.
🞂 In a multi-user system, the same computer
resources hard disk, memory etc. are
accessible to the many users.

14
🞂 Multitasking capability
🞂 Unix is a powerful multi-tasking operating
system.
🞂 Unix can do many jobs at once, dividing
the processor's time between the tasks so
quickly that it looks as if everything is
running at the same time.
🞂 This is called multitasking.
🞂 With a window system, you can have
many applications running at the same
time, with many windows open.
🞂 It means when an active task is in
process, there can be a simultaneous
background process working too.

15
🞂 Communication
⮩ UNIX has the excellent communication with the users.
⮩ The communication may be within the network of a single main computer or between two
or more such computer network.

16
🞂 Security
🞂 Unix Has the three provisions for protecting
the data.
1. Re-assigning the passwords and login
names
2. Read, write and execute permissions
3. File encryption

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🞂 Portability
🞂 Portability means software can work on different types of hardware in same way.
🞂 A portability credit of the UNIX is because of the C language, it written in C
language and C language is portable.

18
Linux Architecture
Hardware
UNIX Operating system(Kernel)
Standard library
Utility Program
User
It contains physical
devices of
computer like CPU,
Memory, Disk,
printer etc.
Provides services
of OS like
memory
management, file
management and
process
management
set of procedures.
Collection of system
level files.
To make user programs
and make work easier,
Like compilers,
assemblers, editors
Comes for
processing and
interact with system

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Components of Linux System
🞂 Kernel
⮩ Kernel is the core part of Linux. It is responsible for all
major activities of this operating system. It consists of
various modules and it interacts directly with the
underlying hardware.
🞂 System Library
⮩ System libraries are special functions or programs using
which application programs or system utilities accesses
Kernel's features.
⮩ These libraries implement most of the functionalities of
the operating system and do not requires kernel
module's code access rights.
🞂 System Utility
⮩ System Utility programs are responsible to do
specialized, individual level tasks.

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Basic function of Kernel
🞂 Resource Allocation
⮩ Manage the computer's resources and allow other programs to
run and use these resources.
⮩ Example: CPU, Memory and I/O devices.
🞂 Process Management
⮩ A process defines which memory portions the application can
access.
⮩ To allow the execution of applications and support them with
features.
Process
1
Process
2
Process
3
Empty
Space
Main
Memory

21
Basic function of Kernel – Cont.
🞂 Memory Management
⮩ It allows processes to safely access this memory as they require it.
⮩ Virtual addressing helps kernel to create virtual partitions of memory in two disjointed
areas.
1. kernel space(reserved for the kernel)
2. User space(for the applications)
Web
brows
er
E-
mail
read
er
Music
player
User Program
Operating System
Softwar
e
Hardwa
re
User
Mod
e
Kern
el
Mod
e
▪User is writing program in C.
▪Once finish writing will execute
it.
▪To execute this program
1. Load program into RAM
2. Program is executed by
processor
user-mode program
performs
trap instruction

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🞂 I/O Device Management
⮩ Processes need access to the peripherals connected to the
computer, which are controlled by the kernel through Device
Drivers.
⮩ It is a computer program that enables the operating system
to interact with a hardware device.
⮩ A kernel maintains a list of available devices.
🞂 Inter- Process Communication
⮩ Its methods for Synchronization and Communication
between processes called Inter- Process Communication
(IPC).
⮩ There are various approaches of IPC say, semaphore, shared
memory, message queue, pipe (or named fifo), etc.

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🞂 Scheduling
⮩ The kernel uses Scheduling Algorithms to
determine which process is running next and
how much time it will be given.
🞂 System Calls and Interrupt Handling
⮩ A system call is a mechanism that is used by
the application program to request a service
from the operating system.
⮩ System calls include close, open, read, wait
and write.
⮩ To access the services provided by the kernel
we need to invoke the related kernel functions.

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🞂 Security or Protection Management
⮩ Kernel also provides protection from faults (error
control) and from malicious behaviours (Security).
⮩ One approach toward this can be language-based
protection system.
⮩ Here, the kernel will only allow code to execute
which has been produced by a trusted language
compiler.

25
Directory Structure
🞂 A directory is a container that is used to contain
folders and file. It organizes files and folders into
a hierarchical manner.
🞂 All the files are grouped together in the directory
structure.
🞂 The top of the hierarchy is traditionally
called root (written as a slash / ).

26
Linux Vs. Windows
✔ Linux is a open source operating system. ✔ Windows are the not the open source operating
system.
✔ Linux is free of cost. No Licence ✔ It is costly. Licence required.
✔ It’s file name case-sensitive. ✔ It’s file name is case-insensitive.
✔ Monolithic kernel is used. ✔ Micro kernel is used.
✔ Linux is customizable. ✔ Windows are not customizable.
✔ There is forward slash is used for separating
the directories.
✔ There is back slash is used for separating the
directories.
✔ Booting possible in either primary or logical
partition.
✔ Booting possible in Only primary partition.
✔ File System: EXT2, EXT3 and EXT4 ✔ File System: FAT, FAT32 and NTFS
Linux Windows

Darshan Institute of Engineering &
Technology, Rajkot
Than
k
You
Operating System (OS)
GTU # 3140702
maulik.trivedi@darshan.ac.in
9998 265 805
Computer Engineering Department

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