ITM-Unix as an OS

8/7/2019 ITM-Unix as an OS

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UNIX AS AN OPERATING

SYSTEM

A Presentation by:Aakriti Batra (2)

Abhishek Bhasin (3)

Ankit Sharma (20)

Arjit Sharma (34)Arpit Bakshi (36)

GROUP NO: 7GROUP NO: 7


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WHAT IS AN OPERATING

SYSTEM? Before understanding UNIX me must understand: What is

operating system first

An operating system is a program which controls all the

parts of a computer system, both the hardware and thesoftware. It allocates the computer resources and scheduletasks

There are variety of operating systems available in

computer market, such as Microsoft MS-DOS, Windows,and Windows NT , IBM OS/2, UNIX, the Apple MacintoshOperating System, and many other popular operatingsystems


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WHAT IS UNIX?

UNIX is a popular time-sharing operating system originally intended

for:

program development

document preparation

but later widely accepted for a number of implementations

UNIX is a multi-user operating system that is found everywhere

today , with no indication of any diminishment in the near future

UNIX is considered the most stable and the most secure operating

system on the market, four decades after its appearance


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UNIX, like any other operating system, is an

integrated collection of programs that act as

links between the computer system and its

users, providing three primary functions:

1.Creating and managing a filesystem (sets of files

stored in hierarchical-structured directories)2.Running programs

3.Using system devices attached to the computer


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HISTORY

Ken Thompson of the Research Group at AT & TBell Laboratories, later joined by Dennis Ritchie, inthe late 1960s developed the first version of UNIX

Derived from MULTICS (1969) i.e., MultiplexedInformation and Computing Service-

It is a mainframe timesharing operating systembegun in 1965 and still in use today

MULTICS began as a research project and was animportant influence on operating systemdevelopment

The system became a commercial product sold by

Honeywell to education, government, and industry

Ken Thompson

Dennis Ritchie


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UNIX DERIVATIVES AND ITS

SUPPLIERS

Sun Microsystems (SunOS/Solaris)

IBM (AIX)

Hewlett Packard (HPUX)

Santa Cruz Organisation (SCO)

Silicon Graphics Inc. (IRIX)

RedHat (Linux)


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FEATURES OF UNIX

UNIX is a:

Multi user operating system, i.e. more than

one user can use the machine at a time

supported via terminals (serial or network

connection)

Multi Multi tasking operating system, i.e., morethan one program can be run at a time,

Multiple users may have multiple tasks

running simultaneously


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Machine independent operating system .

Not specific to just one type of computer hardware. The

System hides the machine architecture from the user, making

it easier to write applications that can run on micros, mini

and mainframes

Portability:

The system is written in high-level language making it easier toread, understand, change and, therefore move to other

machines. The code can be changed and complied on a new

machine. Customers can then choose from a wide variety of

hardware vendors without being locked in with a particular

vendor.


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STRUCTURE OF UNIX

The Unix operating system is made ofthree

parts:

1. The Kernel

2. The Shell

3. The Programs and Utilities


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The KERNEL of UNIX is a hub of the operatingsystem :

it allocates time and memory to programs and handles the file store

communication in response to system.

Enforcessecurity mechanisms

performs all hardware access

1) KERNEL


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2) SHELL

The SHELL acts as an interface between the users andkernel

When a users logs in, the login program checks the

username and password and the starts anotherprogram called shell

The shell is a command line interpreter(CLI)

It interprets the commands the user types in andarranges for them to be carried out

The command are themselves programs: when theyterminate, the shell gives the user another prompt (%

on our program)


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3)THE PROGRAMS AND THE

UTILITIES The system utilities are designed to be powerful tools that do a

single task extremely well (e.g. grep finds text inside files while

wc counts the number of words, lines and bytes inside a file)

System utilities also include server programs called daemonswhich provide remote network and administration services (e.g.

telnetd and sshd provide remote login facilities, lpd provides

printing services, httpd serves web pages, crond runs regular

system administration tasks automatically

file management (rm, cat, ls, rmdir, mkdir)

user management (passwd, chmod, chgrp)

process management (kill, ps)


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FILES AND DIRECTORIES

UNIXs hierarchical file system helps facilitate the sharing andcooperation among users that is so desirable in program-

development environment

UNIX uses a hierarchyto store files

Files are simply a namedcollection of bytes

Directories contain other files

Juliana

File1

Project

File2

File3


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PATHS

A path is a description of how to find something in a file system An absolute path describes a location from the root directory

down

Equivalent to a street address

Always starts with "/"/home/hpotter is Harry Potter's home directory

/courses/swc/wlec/shell.html is this file

A relative path describes how to find something from someother location

Equivalent to saying, "Four blocks north, and seven east"

From /courses/swc, the relative path to this file is

wlec/shell.html


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ACCESSING A UNIX SYSTEM

There are many ways that we can access a UNIX system

The main mode of access to a UNIX machine is through aterminal which usually includes a keyboard and a videomonitor

For each terminal connected to the UNIX system, thekernel runs a process tty that accepts input from theterminal ,and sends output

Tty processors are general programs, and must be told thecapabilities of the terminal in order to correctly read themand write to, the terminal

The name of the program comes from teletypewriter,

abbreviated "TTY"


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TEXT-BASED (TTY) TERMINALS:

When you connect to a UNIX computer remotely (using telnet)or when you log in locally using a text-only terminal, you will see

the prompt:

login:

At this prompt, type in your username and press theenter/return/ key.

Remember that UNIX is case sensitive (i.e. Will, WILL and will

are all different logins). You should then be prompted for your

password:


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Type your password in at the prompt and press theenter/return/ key. Note that your password will not

be displayed on the screen as you type it in

Ifyou mistype your username or password you will

get an appropriate message from the computer andyou will be presented with the login: prompt again.

Otherwise you should be presented with a shell

prompt which looks something like this:

$

To log out of a text-based UNIX shell, type "exit" at

the shell prompt (or if that doesn't work try "logout";

if that doesn't work press ctrl-d)


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GENERAL FORMAT OF UNIX

COMMANDS

A UNIX command line consists of the name of a

UNIX command (actually the "command" is the

name of a built-in shell command, a system

utility or an application program) followed by its

"arguments" (options and the target filenames

and/or expressions). The general syntax for a

UNIX command is :$ command -options targets


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EXECUTION CYCLE

When you type a command like ls, the OS: Reads characters from the keyboard

Passes them to the shell (because it's the currently

active window)

The shell:

Breaks the line of text it receives into words

+ Looks for a program with the same name as the first word

+ Runs that program


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That program's output goes back to the shell... ...which gives it to the OS...

...which displays it on the screen

(Actually, the OS hands it to the window manager, which

takes care of the display)

All well-designed software systems work this way

Break the task down into pieces

Write a tool that solves each sub-problem

Allows you to:

Develop and test components independently

Replace or re-use components incrementally

Add new components as you go along


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ADVANTAGES OF UNIX

Unix is:

more flexible and can be installed on many different types of

machines, including main-frame computers, supercomputers

and micro-computers

more stable and does not go down as often as Windows does,

therefore requires less administration and maintenance

greater built-in security and permissions features thanWindows.

Available on a wide variety of machines - the most truly

portable operating system


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DISADVANTAGES OF UNIX

SOFTWARE While Unix and Unix-like systems have various programs

available for everyday tasks, including image editing or wordprocessing, very few high-profile software companies, such as

Microsoft and Adobe, offer Unix-compatible software

HARDWARE Unix do not necessarily support the same hardware as other

operating systems such as Microsoft Windows and Mac OS X.Whether due to the hardware vendor's unwillingness torelease Unix drivers for the hardware or because theirsystems simply do not support it yet, Unix may not work onthe same hardware configuration as a Windows or OS Xsystem might.


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SUPPORT Although extensive online support is available for Unix,

professional offline support is not as extensive as Windows or

OS X

INTERFACE

The traditional interface for the Unix operating system is

command line based, and this command line shell interface

may be hostile to the casual user. Unix was developed for useby programmers and serious computer users rather than

casual users. A graphical user interface (GUI) is also

available, but the traditional Unix interface is command line


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WINDOWS V/S UNIX (OS):

DIFFERENCES COST : The big difference between UNIX and Window is

cost. Unix is free source code which we can download frominternet but for windows we have to pay Mr. Gates

RELIABILITY : UNIX is more reliable than Windows, and less

administration and maintenance is needed in maintaining aUNIX system. This is a huge cost saver for any organization

SAFETY : Unix is safe, preventing one program fromaccessing memory or storage space allocated to another,and enables protection, requiring users to have permissionto perform certain functions, i.e. accessing a directory, file,or disk drive. Also, UNIX is more secure than Windows on anetwork because Windows is more vulnerable than UNIX.For example, if you leave a port open in Windows it can beeasily used by a hacker to introduce a virus in your

environment


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Both UNIX aka Unixplexed information computing system andwindows are same in some ways:

We can download both windows and unix as client as well as

server that provide services to files serving to other clients in

network. In other words, server client relationship

Both unix and windows can perform multitasking

Both provide management of your process through a GUI(

graphical user interface). Both unix and windows can provide a fullsuite of networking tools and application to allow connection to other

machine and software to allow sharing of files across the network

Both unix and windows have strong built-in security features that

keep unwanted intruders out

SIMILARITIES


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One argument to be made about UNIX is its lack of standardization.

Some feel there are too many choices to be made regarding which GUI

to use, or which combination of UNIX hardware and software to

support

UNIX operating systemsmake great high-performance servers, but

for end-users, every application on each arrangement of UNIX

platform requires a different set, and each application has a different

user interface

Microsoft has "the" Windows operating system; there simply isn't

one standardized UNIX operating system, or for that matter, a single

standardized UNIX GUI. One could argue and say this is a downfall for

UNIX, but on the other hand, these variations add flavor and versatility

to a solid, reliable operating system

CONCLUSION


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ITM-Unix as an OS