Operating System

What is an operating system?

It is a set of program that provide

an

interface between hardware, software

and users and manages all the resources

and provide platform where user can

execute all application/program easily.

Basic function of operating system

Operating

System

Device configurationControls peripheral devices connected to the computer

File managementTransfers files between main memory and secondary storage, manages file folders, backup of file ,recovery of file, protection of file.

Memory managementAllocation and deallocation of memory space.

Decide which process load onto memory when memory

Space become available.

Interface platformProvide the interface b/w hardware, software and users.

Common Operating System Network Operating System

UNIX / Linux / MS Windows2000 Server

Desktop Operating System MS Windows 9X/Me / Mac OS / DOS

Mobile Operating System Palm OS and Pocket PC

Types of Operating System

Batch processingReal time processingTime sharing processing

Batch Processing System

Real Time Operating system

•Immediate response is needed.•For example

anti-missile defense systemairplane landing control systeminterrupt error in computer system

Time Sharing Operating System

Good Operating System

efficient time spent to execute its programs

should be shortsmall in size

memory occupied should be as small as possible

reliable

Special Features of OS

multi-taskingmulti-programmingparallel processingbufferingspooling

Multitasking

Multiprogramming

Parallel Processing

Job 1

Job 2

Job 3

Job 4

Job 1

Job 2

Job 3

Job 4

CPU 1 CPU 2 CPU 1

time

with multiprocessing

Time

Without multiprocessing

Spooling

Components of operating system

Kernel: Core components of the OS Process scheduler

Determines when and for long each process executes

Memory manager Determines when and how memory is allocated

to processes Decides what to do when main memory is full

File system Organizes named collections of data in

persistent storage Networking

Enables processes to communicate with one another

Who is going to attack?

There are various types of intrudersNaïve Users – These are kind of people who have a long nose and have nothing to do. They know less but keep on checking out places for other people’s data (Mails etc.).Skilled Users – These are people like inquisitive students who are more or less skilled and try out ways to access things they are not meant to just for fun or to learn.Purposeful Intruders – These people do nasty jobs on purpose – e.g. Hacking the Military Data of enemy nation, Hacking confidential data of the rival company, etc.

Some well known security threats

Viruses Trojansworms

Some ways to tackle intruders

Passwords – Good passwords – Mixture of numbers, letters of different case is a good security measure. Passwords ideally should not carry any personal information. These steps make it difficult to guess passwords.Periodically changing passwords – Some systems allow us to specify passwords and specify some period within which the password will have to be changed.Recursive Passwords – This is a technology in which each time a password is used, it is re-encrypted or changed automatically. The user is given a list of passwords for a period of time. If that list is secured, the user’s data is secured.

References :

Operating system book by galvin www.wepapers.com www.pucomp.org www.authorstream.com