Operating System 1

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. Discussions will 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 explain them to the class.

5. Explain the different functions of an OS.

Computer SoftwarePage 1 of 17

PC Techn o logy 1

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

Computer Software

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

Computer software is a program or set of instructions that tells the computer what to do. It enables computer hardware to perform specific tasks. If the processor is the brain of the computer, then the software is what the computer thinks (www.pcguide.com).

Application software• programs that are used to

accomplish specific tasks for computer users

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There are two classes of software: system software and application software. System software are programs that control the basic operations of a computer system such as saving files, printing files, accepting input from keyboard, and others. It helps run the computer hardware and computer system. System software includes operating systems, device drivers, utilities, and more. Application softwares, on the other hand, are computer programs that are used to accomplish specific tasks for computer users. Examples of application software are word processors, spreadsheets, presentations, database management software, games, and others.

The succeeding discussions focus on computer operating systems.

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Operating SystemPage 2 of 17

PC Technology 1

Operating System (OS)

software that contains instructions that coordinate all the activities among computer resources

serves as the middleman between applications and hardware

Operating System

Note to the instructor: Before presenting the slide, ask the students first to share what they have read about Operating System. Call on 2 to 3 students to give the definition of Operating System.

An operating system is a system software that manages the hardware (such as processor, memory, hard disk, etc.) and software resources of the computer system. It also provides interface for users to store, retrieve, and manipulate files. For example, operating systems recognize input from the keyboard, keep track of files on the hard disk and control disk drives. In general, an OS acts as an intermediary between software and hardware. General-purpose computers must

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have an operating system installed to run other programs and to allow a user to interact with the computer.

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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 shell is the outer layer while the kernel is the innermost part of the operating system, hence the terms shell and kernel.

OS ComponentsPage 3 of 17 Computer User

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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 checks user’s request for validity and correctness and then passes it to the kernel

Shell

user makes a request to the operating system through the shell

Computer User

Kernel Operating System

shell checks user’s request for validity and correctness and then passes it to the kernel

Shell

user makes a request to the operating system through the shell

kernel performs requested service

Kernel Operating System

kernel performs requested service

Operating System * Property of STIPage 3 of 17 The shell is the portion of the OS that relates to the user and

to applications. That is, in general, it is the shell that the user and applications interact with. It works with the operating system as a command processor, used to enter commands, and initiate the execution. Running applications actually form another layer around the shell so that the user interacts with the application to perform specific (more complicated) tasks.

The kernel is the core of an operating system. This part loads when you first turn on your computer. The kernel controls the computer hardware and performs the basic or low-level services being offered by the operating system. It stays in the memory while the computer is running to help manage memory, maintain the computer clock, start applications and assign resources such as devices, programs, data and information.

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

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Sample OperatingSystemsPage 4 of 17

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Sample OperatingSystems

Each operating system is designed to support 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 operating system is designed to support different types of hardware systems and user needs. The OS links the various elements of the computer system together through common hardware interface, a common programming interface and a common user interface.

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Operating System* Property of STI

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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 drive 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 termed basic disk operating system or BDOS.

The original operating system that came with the IBM PC was called PC-DOS developed by Microsoft. In this case, DOS referred to the operating system being resident on a disk. By some “loophole” in the license agreement between Microsoft and IBM, Microsoft was able to market a better version of PC- DOS called the MS-DOS (Microsoft DOS) which quickly surpassed PC-DOS in popularity. At present, DOS is used to refer to both PC-DOS and MS-DOS in general.

Operating System * Property of STIPage 5 of 17 Below is a screenshot of an MS-DOS 6.0 session. DOS uses

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

DOS is no longer popularly used in lieu of OS’s that use the more user-friendly graphical user interfaces such as Microsoft Windows. However, most Windows OS continue to support DOS to allow users to execute commands and complete specific tasks. In most cases, these are commands that allow finer control over the operating system and/or would be too dangerous to be at easy access of “non-advanced” users.

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UNIXPage 6 of 17

PC Techn o logy 1

Unix

It is a popular OS used to manage networks, 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 UNIXcommand prompt.

[piferr@neverland piferr]$ whoami piferr[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 was designed to be a time-sharing and multi-user system. These capabilities used to be exclusive to the larger mainframe computers. Most major hardware platforms have a proprietary OS derived from Unix such as the AIX for IBM computers and Solaris for Sun Microsystem. It and its derivatives have become the preferred OS among many computer professionals (hackers) and scientists due to system efficiency, stability, and security. (Trivia: The internet and the web were designed according to Unix requirements. Hence, Unix and its derivatives are considered native to the internet and web.)

Operating System * Property of STIPage 6 of 17 Below is a screenshot of a sample Unix command-line

session. 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, and date which shows the current system date and time.

Current versions include a graphical user interface capability.

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LinuxPage 7 of 17

Linux

Linux is a scaled-down version of Unix that was designed to provide a low-cost but efficient and secure operating system for personal computer users. The Open Source status of Linux along with its reputation for reliability, robustness and fast-performing system has made it popular. Various “versions” or “packages” of Linux, called distros (from distribution), exist, including Bayanihan Linux, a distro designed for the Philippines. Linux is also available in commercial versions such as Red Hat, LindowsOS, Slackware, SuSE and others. Below is the famous Linux logo.

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WindowsVersion

Description

Windows 3x Early Windows version including Windows 3.1 and 3.11. It uses the DOS system with a GUI that 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 NT Workstation is used for technical users and Windows NT Server is used for business.

Mac OS Page 8 of 17

Mac OS

Mac OS is available only for Apple Macintosh computers. The Mac OS has long been the model for ease of use and good user interface design. Newer versions also provide features such as built-in networking support and strong multimedia capabilities. Macintosh computers often are used by people working with graphics applications, by students in educational settings and by home users. Below is the Mac OS logo.

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WindowsPage 9 of 17

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Windows

The Windows operating system is the operating system most widely used on today’s personal computers.

Each Windows version developed was designed to provide additional features for specific users including home or business users.

Windows

The Windows operating system is the operating system most widely used on today’s personal computers. Microsoft has developed many versions of the Windows operating systems over the past few decades. Each version was designed to provide additional features for specific users including home and business users. (Windows Vista is the most recent version of Windows as of 2007).

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Windows 9x logo Windows XP,2003 Server andVista logo

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Windows VersionPage 10 of 17

Windows Versions

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Windows VersionsWindowsVersion

Description

Windows 3x Early Windows version including Windows 3.1 and 3.11. It uses the DOS system.

Windows 9xWindows ME (Millennium Edition). WindowsIt includes the Windows 95, Windows 98 and

WindowsNT

It comes in two versions: Windows NT Workstation and Windows NT Server. It is used for businesses and technical users.

Windows2000

An upgrade of Windows NT. It has several versions such as Windows 2000 Professional, Windows 2000 Server, Windows 2000Advanced Server and Windows 2000Datacenter Server.

WindowsXP

It combines the strength of Windows 2000 with the user-friendly features of Windows 98 and Windows ME.

WindowsServer2003

It is a network operating system with additional features for managing and maintaining a network.

WindowsVista

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

Operating System

* Property of STIPage 10 of 17

Windows2000

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

Windows XP It combines the strength of Windows 2000 with the user-friendly features of Windows 98 and Windows ME.

WindowsServer 2003

It is a network operating system with additional features for managing and maintaining a network.

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 Windows operating system. The Windows 3x provided a graphical user interface to what essentially still a DOS system. The Windows9x versions are true operating systems unlike Windows 3x operating environment. The Windows 9x rely on a DOS core while providing a user-friendly interface and advanced features such as Plug and Play (PnP), more integrated Internet capabilities and support for hardware devices such asDVS. (Optional: Plug and Play is a standard designed tomake installation of hardware devices easier allowing the connection of a device to a computer. After which the operating system recognizes that hardware has been changed since the last time the computer was started or while the computer was running. A server is a computer that controls access to the hardware, software and other resources on a network and provides a centralized storage area for programs, data and information.) The Windows NT version on the other hand contains more advanced security features, network support and user administration features. The Windows 2000 version is more of a network operating system, which provides additional features such as network support and increased stability. Windows XP provides an upgraded user interface, support for multiple users, better performance to help programs run faster and more support for multimedia such as audio and video. Windows Server 2003 provides increased security, enhanced file and print server support for remote access and more. Windows Vista is the most recent version of Windows as of 2007. It has updated graphical user interface, advanced multimedia and improved security.

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

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OS Functions

Regardless of the specific type of operating system, the OSperforms key functions such as providing a user interface, managing files and folders, running applications and

OS FunctionsPage 11 of 17

OS Functions

OS provides a user interface

Command-line interface

PC Technology 1

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 a program or waits for its next instruction from a user. If you are working with the OS, you see an interface on the monitor screen. This interface can be a command-line interface, a menu-driven interface or a graphical user interface.

Menu-driven interface Graphical user interface

OS manages files and folders

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Command-line interfaces – With this, you type commands or press specific keys to enter data and command to instruct the OS to perform operations. When working with a command-line interface such as

DOS, the set of commands entered which provides

Operating System * Property of STI

instructions is called command language. Network administrators and other users familiar with these commands use a command-line interface to configure devices, manage system resources and troubleshoot network connections.

Menu-driven interfaces – It provides menus such as a way to enter data and commands. Menu-driven interfaces are easier to learn than command-line interfaces because users do not have to learn the command language used to enter commands. Instead, they just have to select functions from a menu.

Graphical user interfaces – Most of today’s operating system use a graphical user interface (GUI). With GUI, you issue commands by selecting icons, buttons, windows or other graphical objects on screen. When an operating system is started, the initial screen appears with menus, commands and icons. This is called the desktop (in allusion to the work area of the user).

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 a disk, the disk must be formatted. The process of formatting a disk or partition places a file system on the drive. An operating system relies on an organizational method called a file system to use the space available on a disk to store and retrieve files and to store information about the disk’s directory or folder structure. The folder structure is defined during the formatting process.

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OS Manages Applications

An operating system is responsible for managing all other software on the PC including installing and running applications. An application depends on an OS to provide access to hardware resources, manage its data in memory and in secondary storage and perform any background tasks. For example, consider a situation in which Windows XP loads and executes an application. The application cannot run or even load itself without Windows XP, much as a document cannot be edited without a word processing program. Windows XP stays available to the application for the entire time the application is running.

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Installing and loading application software.

Application software typically is distributed on DVD- ROMs, CD-ROMS, or floppy disks or can be downloaded from the Internet. Because application software usually must be installed on a hard drive in order to run, application software comes with an install or setup program that installs the software to a hard drive. During installation, the install program creates folders on the hard drive and copies files to them. For Windows, the software installation process makes entries in the Windows registry, in addition to placing icons on the desktop and adding entries to the Start menu. Once an application is installed, an operating system provides a way to execute or load software. Windows XP provides four ways to load software for example the MS Word as shown in the figures below.

A. Using a Shortcut – double-click shortcut on a desktop

B. Using the Start Menu – click Start button on Windows taskbar, select All Programs and then click program name.

C. Using the Command Prompt – click Start button, click Run or Start menu, and then enter a command line or click browse to search for a program file to execute.

D. Using the Windows Explorer

Handling Multiple Programs

Some operating systems only allow one program to run at a time, while others allow multiple programs to run at once. A single tasking operating system allows only one program to run at a time. For example, if you were working on a spreadsheet and then wanted to check your e-mail, you would have to close the spreadsheet program before starting the e-mail program. DOS, which was used on older PCs, is a single tasking operating system. Today, PDAs and other small computing devices use single tasking operating systems while most PCs use a multitasking operating system. A multitasking operating system allows you to work with two or more programs that reside in memory at the same time. With a multitasking operating system, you could leave the spreadsheet program running while you launch your e-mail program.

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OS FunctionsPage 15 of 17

OS Functions

PC Technology 1

How an OS uses device drivers

Device drivers are small programs stored on the hard drive that tell the computer how to communicate with a specific device such as a printer, network card, or modem. Device drivers are software designed to

OS manages hardware – An OS also is responsible for communicating with hardware.

OS uses device drivers

OS uses system BIOS to manage devices

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interface with specific hardware devices. For example, a printer driver translates the commands sent by the printer to something more understandable by the operating system. A device driver is installed when the OS first is installed or when new hardware is added to the system. An OS provides some device drivers. The manufacturer of a specific hardware device also usually provides device drivers with the hardware device. In either case, unlike BIOS, devicedrivers usually are written for a particular OS.Operating System * Property of STI

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 of hardware devices easier. PnP applies to the OS, the system BIOS, and the hardware devices themselves. With PnP, if you connect a device to your computer, the OS recognizes that hardware has been changed since the last time the computer was started or while the computer was running. Fox example, if you connect a printer to a computer running Windows XP, the OS recognizes the device, determines the system resources needed by each device, and assigns hardware resources appropriately. Windows then determines which drivers are required to support each device and load those drivers. Of all the Windows versions, only Windows 3x and Windows NT do not support PnP.

How an OS uses system BIOS to manage devices.

The basic input/output system (BIOS) on the motherboard is stored on the ROM BIOS chip. The data and instructions stored on the ROM BIOS chip include the system BIOS, startup BIOS and the CMOS BIOS or CMOS setup. The OS communicates with simple devices such as floppy drives or keyboards, through the system BIOS. In addition, the system BIOS is used to access the hard drive. The system BIOS uses the information in CMOS setup to modify or supplement its default programming as needed.

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Booting Up YourComputerPage 16 of 17

Booting Up Your Computer

Before an operating system can perform its functions or communicate using the system resources, it must be loaded from disk to main memory when the computer starts. The process of starting or restarting a computer and loading the operating system is referred to as the boot process or booting.

(Trivia: The original term used is “bootstrapping” in allusion to lifting one’s self by the bootstraps when putting on boots. The process involves a small program built into the PC that loads a small loading module from the secondary storage device. This, in turn, loads the remainder of the OS and then transfers control over to it.)

Booting refers to either cold boot or warm boot. A cold boot or hard boot is turning on the computer that is powered off completely. Hence, the operating system is initialized from scratch. It involves turning on the computer with the on/off power button.

On the other hand, a warm boot or soft boot is the process of restarting a computer that already is powered on. A warm boot re-initializes only parts of the operating system, and under the control of the running operating system. With Windows XP, warm boot can be performed by clicking the Start button, clicking Turn Off Computer and then clicking Restart 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, when the system freezes up, always try using the warm boot first. A cold boot is more stressful on the machine than a warm boot because 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, the cold boot method is performed instead using the on/off button. Avoid turning the computer off and then immediately back on without a pause because this can damage the machine.

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Boot ProcessPage 17 of 17

Boot Process

The functions performed during the boot can be divided into four parts. Startup BIOS is in control for the first step and the beginning of the second step, when control is turned over to the 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, which involves surveying hardware resources and needs, and assigning system resources to meet those needs. The ROM BIOS startup program begins the startup process by reading configuration information stored in the CMOS RAM chip, DIP switches and jumpers and then comparing these information to the available hardware such as the CPU, video card, disk drive, hard drive and so on.

2. The ROM BIOS startup program searches for and loads an OS.

Most often the OS is loaded from drive C on the hard drive. Configuration information on the CMOS RAM chip tells startup BIOS on which devices (and sequence) to look for the OS. Most new BIOS’s support loading the OS from the hard drive, a floppy disk, an optical (CD-ROM or DVD) drive and/or a Zip drive. The BIOS checks the devices in turn, reads the beginning files of the first OS found, copies these into main memory and then turns control over to the OS.

3. The OS configures the system and completes its own loading.

The OS checks some of the same things that startup BIOS checked, such as available memory and whether that memory is reliable. Then the OS loads the software to control a mouse, CD-ROM, scanner and other peripheral devices. These devices generally have device drivers 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 application software automatically, as part of the boot process. To execute an application, the OS must first find the application software on the hard drive or other secondary storage device, copy the software into memory and then turn the control over it.

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