operating syste intro ...1

7/31/2019 operating syste intro ...1

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Operating System


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A special system software that acts as an intermediarybetween a user of a computer and the computer hardware. Provides an environment in which the user can execute

programs/applications in a convenient and efficient manner.

Operating System

User

Operating System

Hardware

Examples of OS: Windows, MS-DOS, Linux, Unix


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Operating System.

Thus the main objectives of an Operating system are:

Make computer convenient to use (hides Hardware details)

Utilize resources in efficient manner

Ability to evolve: If new system functions are introduced that

should not interfere with the service of operating system.


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Functions of an Operating System / Services

provided by an Operating System

Program execution - The system must be ableto load a program into memory and to run thatprogram, end execution, either normally orabnormally (indicating error)

I/O operations - A running program mayrequire I/O, which may involve a file or an I/Odevice.

File-system manipulation - programs need toread and write files and directories, createand delete them, search them, list fileInformation, permission management.


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Functions of an Operating System / Servicesprovided by an Operating System

Communications Processes may exchangeinformation, on the same computer or betweencomputers over a network

Communications may be via shared memory or through

message passing (packets moved by the OS) Error detection OS needs to be constantly aware of

possible errors May occur in the CPU and memory hardware, in I/O devices,

in user program

For each type of error, OS should take the appropriate actionto ensure correct and consistent computing

Debugging facilities can greatly enhance the users andprogrammers abilities to efficiently use the system


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Another set of OS functions exists for ensuring the efficientoperation of the system itself via resource sharing

Resource allocation - When multiple users or multiplejobs running concurrently, resources must be allocated toeach of them

Many types of resources - Some (such as CPUcycles,mainmemory, and file storage) may have specialallocation code, others (such as I/O devices) may havegeneral request and release code.

Accounting - To keep track of which users use how muchand what kinds of computer resources A good operatingsystem keeps usage statistics for various resources and

monitor performance parameters such as response time.For example in windows it gives you information aboutperformance, disk usage or job queues for printing.


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Protection and security - The owners of information stored in a multiuser ornetworked computer system may want to control use of that information,concurrent processes should not interfere with each other

Protection involves ensuring that all access to system resources iscontrolled

Security of the system from outsiders requires user authentication, extendsto defending external I/O devices from invalid access attempts

Protection any mechanism for controlling access of processes or users toresources defined by the OS

Security defense of the system against internal and external attacks including denial-of-service, worms, viruses, identity theft, theft of service

Systems generally first distinguish among users, to determine who can do what

User identities (user IDs, security IDs) include name and associated number,one per user

User ID then associated with all files, processes of that user to determine accesscontrol

Group identifier (group ID) allows set of users to be defined and controlsmanaged, then also associated with each process, file


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Roles of an operating system

The operating system has four main roles:

Control hardware access

Manage files and folders

Provide user interface

Manage applications


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Characteristics of Operating

Systems Control hardware access

OS automatically discovers and configures

PnP hardware

User interface Command line interface (CLI)

Graphical user interface (GUI)


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The Types of Operating Systems

Graphical UserInterface (GUI): The

user interacts with

menus and icons.

Command LineInterface (CLI): The

user types

commands at a

prompt.

Most operating systems include both a GUI and a CLI.


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Types of O/S

Multitasking

Multiprogramming

Time sharing

Multiprocessing


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MULTITASKING O/S

Executing more than one task concurrently.

Execution of two or more tasks/programs by oneuser concurrently on the same computer with onecentral processor.

For example, the user may be running one programand simultaneously listening to a music file.


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Multiprogramming OperatingSystem

Refers to concurrent execution of different usersprograms on a machine with a single processor.

It is the execution of two or more programs

concurrently on a multi-user operating system.

The processor spends a certain amount of timeexecuting each users program. As the processor

works much faster, it seems as though all theprograms are being run at the same time.


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Time SharingOperating System

Round-Robin processing of programs for several users.

A single computer processes the tasks of several usersat different locations based on the concept of time

slicing between the users.


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MultiprocessingOperatingSystem

Simultaneous processing of two or more programs bymultiple computers or processors linked together toperform work simultaneously.

This can involve processing of instructions fromdifferent programs or different instructions within thesame program simultaneously.

Implemented using concepts of parallel processing.


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Desktop Operating System


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Supports a single user or a small group of users.

Some examples of the operating systems in thiscategory are:-

1. MS-DOS:

One of the original operating systems for the IBMPC and its clones.

A non-graphical, line oriented, command-drivenoperating system, with a relatively simple

interface but not a friendly user interface. It was not capable of multitasking. It has now been almost totally replaced by GUI

products such as Windows 95, Windows 98,

Windows 2000 and Windows XP.


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2. Windows 3.1

It is a transition windowing system betweenMS-DOS and Windows95, Windows 98 andWindows 2000.

It is not actually an operating system, but aGUI that operates with, and extends thecapabilities of MS-DOS


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3. Windows 95

The first of a series of products in the Windowsoperating systems that provides a GUI by usingicons to provide instant access to common tasks.

It is a 32-bit operating system that featuresmultitasking, networking, and Internet integrationcapabilities.

It also offers plug-and-play capabilities by enablingthe operating system to recognize new hardwareand install the necessary software (device drivers)automatically.


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4. Windows 98

Offered minor refinements, bug fixes, andenhancements to windows 95.

5. Windows NT

An operating system for high-end desktops andworkstations.

It provides the same GUI as Windows 95, 98, and

2000. Has more powerful multitasking, and memory

management capabilities.

It is popular in networked systems in business

organizations.


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6. Windows 2000

Microsoft changed the name of the upgradeof Windows NT 5.0 to Windows 2000.

This operating system has added securityfeatures.

Runs on multiprocessor computers.

Offers added Internet and Intranetfunctionality.


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8. IBMs OS/2 Operating System

A 32-bit operating system that supportsmultitasking, and supports networked applications.

9. Macintosh Operating System

For Apple Macintosh microcomputers. Is a 32-bit operating system that features

multitasking and powerful graphics capabilities.


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10.Unix

Provides many sophisticated desktop

features, including multiprocessing and

multitasking techniques.

Is valuable to business organizations because

it can be used on many different sizes of

computers ( different hardware: non Intel and

Intel processors).

Was popularized by Sun Microsystems.


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11. Linux

A powerful version of Unix .

Completely free of charge.

It offers multitasking, virtual memory management, andTCP/IP networking.

Originally written by Linus Tovalds at the University ofHelsinki in 1991.

He then released the source code to the world.

Like Unix, it runs on multiple hardware platforms.

Is becoming widely used by Internet service providers.

The clearinghouse for Linux information on the Internet maybe found at www.linuxhq.com


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12.Java Operating System Is designed for hand-held products and

network computers.

Suns java operating system executesprograms written in Java language without the

need for a traditional operating system.

It is designed for Internet and Intranetapplications and embedded devices.



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Departmental Server

OperatingSystems


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The major departmental server operating systemsinclude:-

Unix

Windows NT server

IBMs OS/2 Warp Server

Novell NetWare

IBMs OS/400

Departmental Server OperatingSystems


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Server based operating system

In most common use, a server is a physicalcomputer (a computer hardware system)

dedicated to running one or more services (as

a host),to serve the needs of the users of othercomputers on the network.

Depending on the computing service that it

offers it could be a database server, file

server, mail server, print server,webserver, gaming server, or some other kind of

server.


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Server - Client

In the context of client-server architecture,

a server is a computer program running toserve the requests of other programs, the

"clients".

Thus, the "server" performs some

computational task on behalf of "clients".

The clients either run on the samecomputer or connect through the network.

D l S O i


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Departmental Server OperatingSystems

Although some of these are also desktop OS, all canserve as departmental server OS because of their:-

Strong scalability

Reliability Security Fault tolerance Multitasking

Multiprocessing TCP/IP networking Network management

operating syste intro ...1

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