8/2/2019 mjos

1/26

Introduction to Basic OS Concepts

Submitted to

Mr. Manu

Prepared By

Mayank Joshi

8/2/2019 mjos

2/26

Topics Covered

What is an Operating System?

Mainframe Systems

Desktop Systems Multiprocessor Systems

Distributed Systems

Clustered System Real -Time Systems

Handheld Systems

Computing Environments

8/2/2019 mjos

3/26

What is an Operating System?

A program that acts as an intermediarybetween a user of a computer and the

computer hardware. 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 efficientmanner.

8/2/2019 mjos

4/26

A little insight

Computer systems typically contain:-

Hardware and Software componentsHardware electronic/electric, mechanicalcomponentsSoftware programs and subprograms

Without support softwares, the computer isof very little use

8/2/2019 mjos

5/26

What is an OS?

An interface between Hardware and UserPrograms

An abstraction of the hardware for all the(user) processes

i.e. hides the complexity of the underlyinghardware and give the user a better view of

the computer

8/2/2019 mjos

6/26

Computer System Components

1. Hardware provides basic computing resources (CPU,memory, I/O devices).

2. Operating system controls and coordinates the use of thehardware among the various application programs for thevarious users.

3. Applications programs define the ways in which the systemresources are used to solve the computing problems of theusers (compilers, media players,database systems, videogames, business programs).

4. Users (people, machines, other computers).

8/2/2019 mjos

7/26

Abstract View of SystemComponents

8/2/2019 mjos

8/26

How the OS interacts??

. . .CPU

memory

device device device

Operating system

utilitiesapplications

software

systemssoftware

hardwarecomponents

. . .CPU

memory

device device device

Operating system

utilitiesapplications

software

systemssoftware

hardwarecomponents

8/2/2019 mjos

9/26

Operating System Components

Resource allocator manages andallocates resources.

Control program controls theexecution of user programs andoperations of I/O devices .

Kernel the one program runningat all times (all else beingapplication programs).

8/2/2019 mjos

10/26

The Goals of an OS

Let users run programs:

Correctness

Memory boundaries, priorities, steady state

Convenience

User should not handle the tiny details

(encapsulation/abstraction), providesynchronization primitives, system calls, filesystem, tools

8/2/2019 mjos

11/26

The Goals of an OS

OS lets the users run programs whilefocusing on :

Maximizing Efficiency

Resource Utilization, resource Sharing,Multitasking

Fairness (in resource allocation) Among: users, tasks, resources

The tradeoff between efficiency and fairness

8/2/2019 mjos

12/26

An OS is a Resource Allocator

Its good to share!

Multiple users get all computing resourcessimultaneously: CPU time

Memory (ram, swap, working set, virtual etc)

File system (storage space, primary and secondarystorage devices)

I/O devices (display, printers, mouse,keyboard) Clock

The OS should give every user the illusion thathe/she is getting all resources exclusively (not

sharing!)

8/2/2019 mjos

13/26

What an OS does for a living??

loop forever {

run the process for a while.stop the process and save its state.

load state of another process.

}

8/2/2019 mjos

14/26

Virtual Continuity

A process can get switched in or switched

out.

OS should give the illusion for the process asif it exists in the CPU continuously

=> Context Switching

8/2/2019 mjos

15/26

There are OSs where a process is forced to give upthe CPU (e.g. when stayed for too long).

Such systems implement a preemptive schedulingpolicy.

Examples includeWindows (NT,XP & 7) , Unix etc

Preemptive Scheduling

8/2/2019 mjos

16/26

Most OSs provide the priority mechanism

Priorities are associated with processes

Priorities are used to help the OS reach fairness

Using Priorities

8/2/2019 mjos

17/26

Process

A processis a program in execution.

The components of a process are:

the program to be executed,

the data on which the program will execute,

the resources required by the programsuch as

memory, file(s)and the status of the execution (wait, ready, running).

8/2/2019 mjos

18/26

OS Features Needed for

Multiprogramming I/O routine supplied by the system.

Memory management the systemmust allocate the memory toseveral jobs.

CPU scheduling the system must

choose among several jobs readyto run.

Allocation of devices.

8/2/2019 mjos

19/26

Time-Sharing SystemsInteractive

Computing The CPU is multiplexed among several jobs that are

kept in memory and on disk (the CPU is allocated to

a job only if the job is in memory). A job may be swapped into and out of memory

On-line communication between the user and thesystem is provided; when the operating system

finishes the execution of one command, it seeks thenext control statement from the users keyboard.

8/2/2019 mjos

20/26

Desktop Systems

Personal computers computer system dedicatedto a single user.

I/O devices keyboards, mice, display screens,small printers.

User convenience and responsiveness.

Can adopt technology developed for larger

operating system often individuals have sole useof computer and do not need advanced CPUutilization of protection features.

May run several different types of operatings stems Windows Mac OS UNIX Linux

8/2/2019 mjos

21/26

Distributed Systems

Distribute the computation among several physicalprocessors.

Loosely coupled system each processor has its own localmemory; processors communicate with one another throughvarious communications lines, such as high-speed buses ortelephone lines.

Advantages of distributed systems. Resources Sharing

Computation speed up load sharing

Reliability

Communications

8/2/2019 mjos

22/26

Distributed Systems (cont)

Requires networking infrastructure.

Local area networks (LAN) or Widearea networks (WAN)

May be either client-server or peer-

to-peer systems.

8/2/2019 mjos

23/26

Major Computer OSs

Windows by Microsoft Corp.

Unix

Linux(freeware with openSUSE,redhat andUbuntu distributions)

MacOS by Apple Inc.

Solaris by Sun Microsystems

8/2/2019 mjos

24/26

Leading Mobile OSs

Windows Mango,Windows mobile for PDAs

iOS for iPhones

Android by Google for touch screen devices

(tablets and smartphones)

Symbian OS (s30,s40,s60, anna and belle) byNokia

PalmOS Meego

BADA by Samsung

8/2/2019 mjos

25/26

Sources

www.wikipedia.com

www.google.co.in

www.microsoft.com www.linuxdeveloperforum.com

www.apple.inc

http://www.google.co.in/http://www.microsoft.com/http://www.linuxdeveloperforum.com/http://www.apple.inc/http://www.apple.inc/http://www.linuxdeveloperforum.com/http://www.microsoft.com/http://www.google.co.in/

8/2/2019 mjos

26/26

THANK YOU