2. Road Map
Unix Biography
Unix System Organization
Evolution of Unix
Kernel/Shell
What is Unix?
Why do I need to know Unix?
File Management
Login in Unix
Architecture of Unix.
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3. Unix Biography
1964 joint project between AT&T Bell Labs, GE, and MIT to
develop a new OS
Goal : develop an OS that could provide computational
power, data storage and the ability to share data among
multiple users
Result: Multiplexed Information & Computer Service MULTICS.
4. Unix Biography
1969 Bell Labs withdraws from group, Two Bell Lab
scientists, Ken Thompson and Dennis Ritchie, continue
research.
At the same time Ken Thompson wrote a game “space
travel” in Fortran to run on GECOS OS
Thompson ported the game to a little used PDP-7 computer
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5. Unix Biography-PDP-7
In 1969, Ken Thompson wrote the first UNIX system in
assembly language on a PDP-7, then named Unics as a pun
on Multics
It’s as the operating system for Space Travel, a game
which required graphics to depict the motion of the
planets
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6. Unix History
Here’s Unix history
1969
1976
1978
1991
Creation by Ken
Thompson and
Denis Ritchie from
Bell Labs
Creation of
Apple
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Creation of Linux
by Linus Torvalds
Split between
BSD and type V
Unix
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7. What is Unix
The low-level software which handles the interface to system
hardware (input/output devices, memory, file system, etc),
schedules tasks, and provides common core services such as a
basic user interface.
It’s portable, multi-tasking and multi-user operating system
Portable: runs on many different hardware architectures
(Intel x86, Motorola 680x0etc.).
Pre-emptive multi-tasking: several programs can run at the
same time (time slices, interrupts, and task switching.
Multi-user: many users can share the computer system at
the same time
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8. What is Unix – Other Features
Uses a simple, uniform file model which includes devices
and access to other services in a flexible, hierarchical file
system.
Written in a high-level language (“C”) making it easy to
read, understand, change and port.
The command prompt is a simple user process, the Unix
shell, which is also a convenient job programming language.
Includes support for regular expressions which are
convenient for complex searching.
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9. What is Unix –Philosophy
Philosophy of Unix system
• Everything is a file
– Hard Drive, CDROM drive, CPU …
• Task segmentation
• A program must be portable
• Write code quickly and to share with the
community
• Correct bugs quickly
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10. Unix Features
Multi- user
Hierarchical file system
Multi tasking
Threads
Virtual memory
Built –in networking
Extensive set of utilities
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11. Unix Merits /Demerits
True multi-tasking
Not that User friendly
Flexible/Portable
Sleep learning curve
“Nice”
Programming Events
Not 100% compatible
with the Microsoft world.
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12. Top ten points
why I need to use
Unix ??
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13. # Unix is more flexible and can
be installed on many different
types of machines, including
main-frame computers,
supercomputers and microcomputers.
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14. #2 – Scalability
• Unix is more stable and
does not go down as often as
Windows does, therefore requires
less administration and
maintenance.
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15. #3 – security
• Unix has greater built-in security
and permissions features than
Windows.
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16. #4 – Compatibility
Web sites designed and programmed
to be served under a UNIX-based
web server can easily be hosted on
a Windows server,
whereas the reverse is not always true.
This makes programming for
UNIX the better choice
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17. #5 – Stability
Servers running on UNIX enjoy
extremely high up-time and high
availability/reliability
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18. #6 – Performance
UNIX servers under high load
(which is what is important)
are superior to Windows
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19. #7 – Command line
• The command line will always
be an invaluable tool for
administration purposes.
Nothing will ever replace
favorite text-based editor
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20. #8 – Software Updates
• software upgrades from Microsoft
often require the user to purchase
new or more hardware or
prerequisite software.
That is not the case with Unix.
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21. #9 – Price
• The mostly free or inexpensive
open-source operating systems,
such as Linux and BSD.
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22. #10 – Data security
Users are required to log in
before they can do anything.
Logging in restricts
unauthorised use, allows all files
created by a user to be
identified as belonging to them
and, if necessary, only visible to
that user
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23. Unix - Quiz
The BSD system is a different Unix system
MacOSX is not based on the Unix system
UNIX system is a multi-task system
UNIX system is a multi-user system
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25. Unix
Unix System follows a layered Approach
It has four layers
The innermost layer is the hardware layer
In the second layer, the kernel is placed.
The utilities and the other application programs
form the third layer
Fourth layer is the one with which the user
actually interacts.
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26. Unix – Kernel
Kernel is that part of the OS which directly makes
interface with the hardware system.
Factions:
Provides mechanism for creating and deleting
processes
Provides processor scheduling, memory and IO
management
Does interprocess communication.
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27. Unix – Shell
Shell
Whenever you login to a Unix system you are placed in
a shell program.
The shell's prompt is usually visible at the cursor's
position on your screen. To get your work done, you
enter commands at this prompt.
The shell is a command interpreter;.
It takes each command and passes it to the operating
system kernel to be acted upon.
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28. Types of Shell
Bourne shell (sh)
Shell
C shell (csh)
Korn shell (ksh)
Kron Shell
Bournce Shell
C shell
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29. Unix - Shell
A Utility program that comes with the unix system.
Features of Shell are:
Interactive Processing
Background Processing
I/O Redirection
Pipes
Shell Scripts
Shell Variables
Programming Constructs
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30. Unix
Bourne Shell(sh) – This is the original shell of UNIX which
comes with every UNIX sytem and may be that is the
reason that it is so popular.It was written by Stephen
Bourne at Bell Labs in 1974
• C shell(csh) – It has a syntax that resembles that of the
highly popular C programming language (also developed at
Bell Labs), and thus it is sometimes preferred by
programmers.
Korn shell(ksh) – It is a superset of sh developed by David
Korn at Bell Labs in 1983. It contains many features of the
C shell as well, including a command historys
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31. MS Windows Vs UNIX
C:
/
N:
sue
ollie
cdrom
floppy
users
local
dan
ollie
sue
dan
mail
exec
A:
D:
N:danexec
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mail
exec
/users/dan/exec
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32. Unix
[1] Absolute location:
/users/dan/mail/my.doc
[2] Relative to the directory
“sue”
../dan/mail/my.doc
/
cdrom
floppy
users
local
dan
ollie
sue
[3] For Dan, relative to his
homespace:
~/mail/my.doc
[4] For everyone else, relative
to Dan’s homespace:
mail
exec
my.doc
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33. Unix - File Management
Unix uses a hierarchical file system with “/” as its root.
Every non-leaf node of the tree is called as a directory
file.
Every leaf node can either be a file or an empty directory
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34. Unix – CPU Scheduling
Unix uses “Round-Robin” scheduling to support its multiuser and time-sharing feature.
Round-Robin fashion of scheduling is considered to be
oldest,simplest and widely used algorithm.
Here, every process is given a time slice(10-100 millisec.)
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35. What can UNIX do for you ?
Departmental E-mail
World Wide Web
Scientific Programming
1.FORTRAN
2.C/C++
3.Matlab
4.Maple
Text Processing
Plotting packages
1.Gnuplot
2.tecplot
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36. Unix
Super User
Group 2
Group 1
Owner
Group
member
Group
member
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others
others
others
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37. Unix -Log in
you will need to have a valid username and a password
Type your username at the login prompt
UNIX is case sensitive
When the password prompt appears, type in your
password.
Your password is never displayed on the screen as
a security measure
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39. Unix - How to change the passwords
passwd command
Old password: - enter your current password
New password: - enter your new password
Retype new password: - re-enter your new password
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40. Unix -Logging Off The System
– To logout enter the command logout or exit.
– If this does not work, press Ctrl-d.
– If you have a .logout file in your home directory, the system
will execute any commands contained there.
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41. Unix - Stop and Think
Do you have any questions ?
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