7 Operating System

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Installing Computer Systems and Networks

Operating System *Property of STIPage 1 of 15

TOPIC TITLE: OPERATING SYSTEM

SPECIFIC OBJECTIVES:

At the end of the topic session, the students are expected to:

Cognitive:

1. Explain what an operating system is2. Identify the components of operating system3. Explain the different functions of the operating system4. Identify the types of operating system

Affective:

1. Listen to others with respect2. Participate in class discussions actively

MATERIALS/EQUIPMENT:

1. topic slides2. OHP

TOPIC PREPARATION:

Have the students research the following:

Definition of operating system

Different types of operating system Components of operating system Functions of operating system

Boot Process

Online Reference:

http://www.howstuffworks.com

TOPIC PRESENTATION:

The topic will revolve around operating system. Discussionswill include operating system (OS) components, OS operation,OS functions and types of OS.

Guide Questions:1. What is an operating system?2. Explain briefly the components of OS.3. What are the functions of OS?

This will be the suggested flow of discussion for OperatingSystem.

1. Explain what an operating system (OS) is.2. Discuss the different components of an OS.3. Discuss the operation of an OS.4. Identify the types of OS.

Show the slides with captured screenshots and explainthem to the class.

5. Explain the different functions of an OS.


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Computer SoftwarePage 1 of 17

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Page1of17OperatingSystem

Computer Software

a program or set of instructions that tells

the computer what to do

System software programs that control the basic

operations of a computer system

Application software programs that are used to

accomplish specific tasks for

computer users

Computer Software

Note to the instructor: Ask the students to define what acomputer software (or simply software) is.

Computer sof tware is a program or set of instructions thattells the computer what to do. It enables computer hardwareto perform specific tasks. If the processor is the brain of thecomputer, then the software is what the computer thinks(www.pcguide.com).

There are two classes of software: system software andapplication software. System software are programs thatcontrol the basic operations of a computer system such assaving files, printing files, accepting input from keyboard, andothers. It helps run the computer hardware and computersystem. System software includes operating systems, devicedrivers, utilities, and more. Application softwares, on the other

hand, are computer programs that are used to accomplishspecific tasks for computer users. Examples of applicationsoftware are word processors, spreadsheets, presentations,database management software, games, and others.

The succeeding discussions focus on computer operatingsystems.

[Computer Software, Page 1 of 17]

Operating SystemPage 2 of 17

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P age2of17OperatingSystem

Operating System (OS)

software that contains instructions that

coordinate all the activities among

computer resources

serves as the middleman betweenapplications and hardware

Operating System

Note to the instructor: Before presenting the slide, ask the

students first to share what they have read about OperatingSystem. Call on 2 to 3 students to give the definition ofOperating System.

An operating system is a system software that manages thehardware (such as processor, memory, hard disk, etc.) andsoftware resources of the computer system. It also providesinterface for users to store, retrieve, and manipulate files. Forexample, operating systems recognize input from thekeyboard, keep track of files on the hard disk and control diskdrives. In general, an OS acts as an intermediary betweensoftware and hardware. General-purpose computers musthave an operating system installed to run other programs and

to allow a user to interact with the computer.

[Operating System, Page 2 of 17]

OS Components

An operating system can be divided into two parts: shell andkernel. The figure below shows the relationship between theuser, the shell, and the kernel. As seen in the figure, the shellis the outer layer while the kernel is the innermost part of theoperating system, hence the terms shell and kernel.


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OS ComponentsPage 3 of 17

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OS Components

Every operating system has two main

internal components:

Shell relates to the user and to applications

Kernel core of an operating system

Shell

Kernel OperatingS ystem

Computer User

usermakesarequesttotheoperatingsystemthroughthe shell

shellchecks

users requestforvalidityand

correctnessandthenpassesitto

thekernel

kernelperformsrequestedservice

Shell

Kernel Operating System

Computer User

user makes a request to the

operating system through the shell

shell checks

users request for

validity and

correctness and

then passes it to

the kernel

kernel performs

requested service

The shellis the portion of the OS that relates to the user andto applications. That is, in general, it is the shell that the user

and applications interact with. It works with the operatingsystem as a command processor, used to enter commands,and initiate the execution. Running applications actually formanother layer around the shell so that the user interacts withthe application to perform specific (more complicated) tasks.

The kernelis the core of an operating system. This part loadswhen you first turn on your computer. The kernel controls thecomputer hardware and performs the basic or low-levelservices being offered by the operating system. It stays in thememory while the computer is running to help managememory, maintain the computer clock, start applications andassign resources such as devices, programs, data and

information.

The kernel is considered to be memory resident because itstays in memory while the computer is running. However,other parts of the operating system may be nonresident andare stored in secondary storage (typically on the hard disk)until they are needed.

[OS Components, Page 3 of 17]

Sample OperatingSystemsPage 4 of 17

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Sample Operating

Systems

Each operating system is designed tosupport different types of hardware

systems and user needs.

Disk Operating System (DOS)

Windows

Unix

Linux

Mac OS

Sample Operating Systems

Several operating systems are available today. Among those

popular (or used to be) for personal computing are DOS,Windows, Mac OS, Unix, Linux and OS/2. Each operatingsystem is designed to support different types of hardwaresystems and user needs. The OS links the various elementsof the computer system together through common hardwareinterface, a common programming interface and a commonuser interface.

[Sample Operating Systems, Page 4 of 17]


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DOSPage 5 of 17

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Disk Operating System

(DOS)

It is the first OS used for IBM and IBM-

compatible computers.

It uses a command-line interface where

the user has to enter specific commands.

C:\>dir

Volume in driv e C is MS-DOS 6_0Volume Serial Number is 446B -2781Directory of C:\

COMMAND COM 52925 03-10-93 6:00a1 file(s) 52925 bytes

10219520 bytes free

C:\>ver

MS-DOS Version 6.00

C:\>

DOS

Early operating systems were designed simply to control how

you read from, write to files and disks, and were hence termedbasic disk operating system or BDOS.

The original operating system that came with the IBM PC wascalled PC-DOS developed by Microsoft. In this case, DOSreferred to the operating system being resident on a disk. Bysome loophole in the license agreement between Microsoftand IBM, Microsoft was able to market a better version of PC-DOS called the MS-DOS (Microsoft DOS) which quicklysurpassed PC-DOS in popularity. At present, DOS is used torefer to both PC-DOS and MS-DOS in general.

Below is a screenshot of an MS-DOS 6.0 session. DOS uses

a command-line interface where the user has to enter or typespecific commands at a system prompt (C:\> in this case).The example shows the execution of the commands dir andver. The first lists the contents of the currently selected disk(drive C: as indicated by the prompt) while the second showsthe version of MS-DOS loaded. The last line shows theprompt while waiting for user input.

DOS is no longer popularly used in lieu of OSs that use themore user-friendly graphical user interfaces such as MicrosoftWindows. However, most Windows OS continue to supportDOS to allow users to execute commands and completespecific tasks. In most cases, these are commands that allowfiner control over the operating system and/or would be toodangerous to be at easy access of non-advanced users.

[DOS, Page 5 of 17]


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UNIXPage 6 of 17

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OperatingSystem

Unix

It is a popular OS used to managenetworks, support multiple users, to handle

a high volume of instruction and to support

applications used on the Internet.

It is an open source OS.

Below is a screenshot of a sample UNIX

command prompt.

[piferr@neverland piferr]$ whoamipiferr[piferr@neverland piferr]$ ls

public_html stuff[piferr@neverland piferr]$ date

Wed Jul 14 15:50:41 EDT 2007[piferr@neverland piferr]$

UNIX

Originally written on a 16-bit PDP-7 minicomputer, Unix wasdesigned to be a time-sharing and multi-user system. Thesecapabilities used to be exclusive to the larger mainframecomputers. Most major hardware platforms have a proprietaryOS derived from Unix such as the AIX for IBM computers andSolaris for Sun Microsystem. It and its derivatives havebecome the preferred OS among many computerprofessionals (hackers) and scientists due to systemefficiency, stability, and security. (Trivia: The internet and theweb were designed according to Unix requirements. Hence,Unix and its derivatives are considered native to the internetand web.)

Below is a screenshot of a sample Unix command-linesession. This shows the prompt and the execution of three

commands: whoami which identifies the current user, ls

which displays the contents of the current directory, anddate

which shows the current system date and time.

Current versions include a graphical user interface capability.

[UNIX, Page 6 of 17]

LinuxPage 7 of 17

Linux

Linux is a scaled-down version of Unix that was designed toprovide a low-cost but efficient and secure operating systemfor personal computer users. The Open Source status ofLinux along with its reputation for reliability, robustness andfast-performing system has made it popular. Variousversions or packages of Linux, called distros (fromdistribution), exist, including Bayanihan Linux, a distro

designed for the Philippines. Linux is also available incommercial versions such as Red Hat, LindowsOS,Slackware, SuSE and others. Below is the famous Linux logo.

[Linux, Page 7 of 17]


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Mac OSPage 8 of 17

Mac OS

Mac OS is available only for Apple Macintosh computers. TheMac OS has long been the model for ease of use and gooduser interface design. Newer versions also provide featuressuch as built-in networking support and strong multimediacapabilities. Macintosh computers often are used by peopleworking with graphics applications, by students in educationalsettings and by home users. Below is the Mac OS logo.

[Mac OS, Page 8 of 17]

WindowsPage 9 of 17

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Windows

The Windows operating system is the

operating system most widely used ontodays personal computers.

Each Windows version developed wasdesigned to provide additional features for

specific users including home or business

users.

Windows 9x logo Windows XP,

2003 Server and

Vista logo

Windows

The Windows operating system is the operating system mostwidely used on todays personal computers. Microsoft hasdeveloped many versions of the Windows operating systemsover the past few decades. Each version was designed toprovide additional features for specific users including homeand business users. (Windows Vista is the most recentversion of Windows as of 2007).

[Windows, Page 9 of 17]

Windows VersionPage 10 of 17

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Windows Versions

It combines the strength of Windows 2000 with

the user-friendly features of Windows 98 and

Windows ME.

Windows

XP

It is a network operating system with additional

features for managing and maintaining a

network.

Windows

Server

2003

It is the most recent version of Windows as of

2007. It has updated graphical user interface,

advanced multimedia and improved security.

Windows

Vista

An upgrade of Windows NT. It has several

versions such as Windows 2000 Professional,

Windows 2000 Server, Windows 2000

Advanced Server and Windows 2000

Datacenter Server.

Windows

2000

It comes in two versions: Windows NT

Workstation and Windows NT Server. It is

used for businesses and technical users.

Windows

NT

It includes the Windows 95, W indows 98 and

Windows ME (Millennium Edition). Windows

9x rely on a DOS core.

Windows 9x

Early Windows version including Windows 3.1

and 3.11. It uses the DOS system.

Windows 3x

DescriptionWindows

Version

Windows Versions

WindowsVersion

Description

Windows 3x Early Windows version including Windows 3.1and 3.11. It uses the DOS system with a GUIthat runs on top.

Windows 9x It includes the Windows 95, Windows 98, andWindows ME (Millennium Edition). Windows9x rely on a DOS core.

Windows NT It comes in two versions: Windows NTWorkstation is used for technical users andWindows NT Server is used for business.


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Windows2000

An upgrade of Windows NT. It has severalversions such as Windows 2000 Professional,Windows 2000 Server, Windows 2000

Advanced Server and Windows 2000Datacenter Server.

Windows XP It combines the strength of Windows 2000 withthe user-friendly features of Windows 98 andWindows ME.

WindowsServer 2003

It is a network operating system with additionalfeatures for managing and maintaining anetwork.

WindowsVista

It is the most recent version of Windows as of2007. It has updated graphical user interface,advanced multimedia, and improved security.

The table above shows the various versions of the Windowsoperating system. The Windows 3x provided a graphical userinterface to what essentially still a DOS system. The Windows9x versions are true operating systems unlike Windows 3xoperating environment. The Windows 9x rely on a DOS corewhile providing a user-friendly interface and advancedfeatures such as Plug and Play (PnP), more integratedInternet capabilities and support for hardware devices such asDVS. (Optional: Plug and Play is a standard designed tomake installation of hardware devices easier allowing theconnection of a device to a computer. After which theoperating system recognizes that hardware has been changedsince the last time the computer was started or while the

computer was running. A server is a computer that controlsaccess to the hardware, software and other resources on anetwork and provides a centralized storage area for programs,data and information.) The Windows NT version on the otherhand contains more advanced security features, networksupport and user administration features. The Windows 2000version is more of a network operating system, which providesadditional features such as network support and increasedstability. Windows XP provides an upgraded user interface,support for multiple users, better performance to helpprograms run faster and more support for multimedia such asaudio and video. Windows Server 2003 provides increasedsecurity, enhanced file and print server support for remote

access and more. Windows Vista is the most recent versionof Windows as of 2007. It has updated graphical userinterface, advanced multimedia and improved security.

Note to the instructor: Research on the features of WindowsVista and discuss this on class. Encourage the students toshare what they know about Windows Vista.

[Windows Version, Page 10 of 17]

OS Functions

Regardless of the specific type of operating system, the OS

performs key functions such as providing a user interface,managing files and folders, running applications and


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OS FunctionsPage 11 of 17

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OperatingSystem

OS Functions

OS provides a user interface

OS manages files and folders

Command-line

interface

Menu-driven interface Graphical user interface

managing hardware.

OS Provides a User Interface

When a PC first is turned on, the operating system is loaded.After the OS is in control, it either automatically executes aprogram or waits for its next instruction from a user. If you areworking with the OS, you see an interface on the monitorscreen. This interface can be a command-line interface, amenu-driven interface or a graphical user interface.

Command-line interfaces With this, you typecommands or press specific keys to enter data andcommand to instruct the OS to perform operations.When working with a command-line interface such asDOS, the set of commands entered which providesinstructions is called command language. Networkadministrators and other users familiar with these

commands use a command-line interface to configuredevices, manage system resources and troubleshootnetwork connections.

Menu-driven interfacesIt provides menus such as away to enter data and commands. Menu-driveninterfaces are easier to learn than command-lineinterfaces because users do not have to learn thecommand language used to enter commands.Instead, they just have to select functions from amenu.


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Graphical user interfaces Most of todays operatingsystem use a graphical user interface (GUI). WithGUI, you issue commands by selecting icons, buttons,windows or other graphical objects on screen. Whenan operating system is started, the initial screenappears with menus, commands and icons. This iscalled the desktop (in allusion to the work area of theuser).

OS Manages Files and Folders

An operating system is responsible for storing and organizing

files on a secondary storage medium such as a CD-ROM,floppy disk or hard disk. Before any files can be stored on adisk, the disk must be formatted. The process of formatting adisk or partition places a file system on the drive. Anoperating system relies on an organizational method called afile system to use the space available on a disk to store andretrieve files and to store information about the disks directoryor folder structure. The folder structure is defined during theformatting process.

[OS Functions, Page 11 of 17]

OS Manages Applications

An operating system is responsible for managing all othersoftware on the PC including installing and runningapplications. An application depends on an OS to provideaccess to hardware resources, manage its data in memoryand in secondary storage and perform any background tasks.For example, consider a situation in which Windows XP loadsand executes an application. The application cannot run oreven load itself without Windows XP, much as a documentcannot be edited without a word processing program.Windows XP stays available to the application for the entiretime the application is running.


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OS FunctionsPages 12 to 14 of 17

Installing and loading application software.

Application software typically is distributed on DVD-ROMs, CD-ROMS, or floppy disks or can bedownloaded from the Internet. Because applicationsoftware usually must be installed on a hard drive inorder to run, application software comes with an installor setup program that installs the software to a harddrive. During installation, the install program createsfolders on the hard drive and copies files to them. ForWindows, the software installation process makesentries in the Windows registry, in addition to placingicons on the desktop and adding entries to the Startmenu. Once an application is installed, an operatingsystem provides a way to execute or load software.Windows XP provides four ways to load software forexample the MS Word as shown in the figures below.

A. Using a Shortcut double-click shortcut on adesktop

B. Using the Start Menu click Start button onWindows taskbar, select All Programs and thenclick program name.


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C. Using the Command Prompt click Start button,click Run or Start menu, and then enter acommand line or click browse to search for aprogram file to execute.

D. Using the Windows Explorer

Handling Multiple Programs

Some operating systems only allow one program torun at a time, while others allow multiple programs torun at once. A single tasking operating system allowsonly one program to run at a time. For example, if youwere working on a spreadsheet and then wanted tocheck your e-mail, you would have to close thespreadsheet program before starting the e-mailprogram. DOS, which was used on older PCs, is a

single tasking operating system. Today, PDAs andother small computing devices use single taskingoperating systems while most PCs use a multitaskingoperating system. A multitasking operating systemallows you to work with two or more programs thatreside in memory at the same time. With amultitasking operating system, you could leave thespreadsheet program running while you launch youre-mail program.

[OS Functions, Pages 12 to 14 of 17]


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OS FunctionsPage 15 of 17

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OperatingSystem

OS Functions

OS manages hardware An OS also isresponsible for communicating with

hardware.

OS uses device drivers

OS uses system BIOS to managedevices

How an OS uses device drivers

Device drivers are small programs stored on the harddrive that tell the computer how to communicate witha specific device such as a printer, network card, ormodem. Device drivers are software designed tointerface with specific hardware devices. Forexample, a printer driver translates the commandssent by the printer to something more understandableby the operating system. A device driver is installedwhen the OS first is installed or when new hardware isadded to the system. An OS provides some devicedrivers. The manufacturer of a specific hardwaredevice also usually provides device drivers with thehardware device. In either case, unlike BIOS, devicedrivers usually are written for a particular OS.

Installing a device in a system that supports Plug and

Play usually is a simple process. Plug and Play (PnP)is a standard designed to make installation ofhardware devices easier. PnP applies to the OS, thesystem BIOS, and the hardware devices themselves.With PnP, if you connect a device to your computer,the OS recognizes that hardware has been changedsince the last time the computer was started or whilethe computer was running. Fox example, if youconnect a printer to a computer running Windows XP,the OS recognizes the device, determines the systemresources needed by each device, and assignshardware resources appropriately. Windows thendetermines which drivers are required to support each

device and load those drivers. Of all the Windowsversions, only Windows 3x and Windows NT do notsupport PnP.

How an OS uses system BIOS to manage devices.

The basic input/output system (BIOS) on themotherboard is stored on the ROM BIOS chip. Thedata and instructions stored on the ROM BIOS chipinclude the system BIOS, startup BIOS and theCMOS BIOS or CMOS setup. The OS communicateswith simple devices such as floppy drives orkeyboards, through the system BIOS. In addition, the

system BIOS is used to access the hard drive. Thesystem BIOS uses the information in CMOS setup tomodify or supplement its default programming asneeded.

[OS Functions, Page 15 of 17]


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Booting Up YourComputerPage 16 of 17

Booting Up Your Computer

Before an operating system can perform its functions orcommunicate using the system resources, it must be loadedfrom disk to main memory when the computer starts. Theprocess of starting or restarting a computer and loading theoperating system is referred to as the boot processor booting.

(Trivia: The original term used is bootstrapping in allusion tolifting ones self by the bootstraps when putting on boots. Theprocess involves a small program built into the PC that loads asmall loading module from the secondary storage device.This, in turn, loads the remainder of the OS and then transferscontrol over to it.)

Booting refers to either cold boot or warm boot. A cold boot orhard boot is turning on the computer that is powered offcompletely. Hence, the operating system is initialized from

scratch. It involves turning on the computer with the on/offpower button.

On the other hand, a warm boot or soft boot is the process ofrestarting a computer that already is powered on. A warmboot re-initializes only parts of the operating system, andunder the control of the running operating system. WithWindows XP, warm boot can be performed by clicking theStart button, clicking Turn Off Computer and then clickingRestart as shown in the figure below.

Clicking the Restart button performs a warm boot.

If there is a need to reboot the computer, for example, whenthe system freezes up, always try using the warm boot first. Acold boot is more stressful on the machine than a warm bootbecause of the initial power surge through the equipment.Besides, a warm boot is also faster since fewer initializations

are performed. If the warm boot method does not work, thecold boot method is performed instead using the on/off button.

Avoid turning the computer off and then immediately back onwithout a pause because this can damage the machine.

[Booting Up Your Computer, Page 16 of 17]


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Boot ProcessPage 17 of 17

Boot Process

The functions performed during the boot can be divided intofour parts. Startup BIOS is in control for the first step and thebeginning of the second step, when control is turned over tothe OS.

1. Startup BIOS runs a process called the power-on self test(POST) and assigns system resources.

The ROM BIOS startup program performs a POST, whichinvolves surveying hardware resources and needs, andassigning system resources to meet those needs. TheROM BIOS startup program begins the startup process byreading configuration information stored in the CMOSRAM chip, DIP switches and jumpers and then comparingthese information to the available hardware such as theCPU, video card, disk drive, hard drive and so on.

2. The ROM BIOS startup program searches for and loadsan OS.

Most often the OS is loaded from drive C on the harddrive. Configuration information on the CMOS RAM chiptells startup BIOS on which devices (and sequence) tolook for the OS. Most new BIOSs support loading the OSfrom the hard drive, a floppy disk, an optical (CD-ROM orDVD) drive and/or a Zip drive. The BIOS checks thedevices in turn, reads the beginning files of the first OSfound, copies these into main memory and then turnscontrol over to the OS.

3. The OS configures the system and completes its ownloading.

The OS checks some of the same things that startupBIOS checked, such as available memory and whetherthat memory is reliable. Then the OS loads the softwareto control a mouse, CD-ROM, scanner and otherperipheral devices. These devices generally have devicedrivers stored on the hard drive. In case of Windows OS,the Windows desktop is loaded.

4. Application software is loaded and executed.

Sometimes an OS is configured to launch applicationsoftware automatically, as part of the boot process. Toexecute an application, the OS must first find theapplication software on the hard drive or other secondarystorage device, copy the software into memory and thenturn the control over it.

[Boot Process, Page 17 of 17]


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REFERENCES:

Mueller, Scott, (2006), Upgrading and repairing PCs(17th ed.),Que Publishing

Gookin, Dan, (2005), Troubleshooting your PC for dummies(2nd ed.), Wiley Publishing, Inc.

Press, B. and Press, M., (2004), PC upgrade and repair bible:desktop edition, Wiley Publishing, Inc.

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7 Operating System