Definition
An Operating System is a software program or set of programs that mediate access between physical devices (such as a keyboard, mouse, monitor, disk drive or network connection) and application programs (such as a word processor, World-Wide Web browser or electronic mail client).
The operating system and its various components act as bridge between the users and computer. The user can easily interact with the computer system. The operating system also act as resource manager allocating different resources like memory and I/O devices to various programs and jobs that we required by the user.

The Purpose of Operating Systems
An operating system (OS) is a software program, but it is different from word processing programs, spreadsheets, and all the other software programs on your computer. As you may recall from Chapter 1, the OS is an example of system software—software that controls the system’s hardware and that interacts with the user and application software. In short, the operating system is the computer’s master control program. The OS provides you with the tools (commands) that enable you to interact with the PC. When you issue a command, the OS translates it into code that the machine can use. The OS ensures that the results of your actions are displayed on screen, printed, and so on. The operating system also acts as the primary controlling mechanism for the computer’s hardware.
The operating system performs the following functions:
ü Displays the on-screen elements with which you interact—the user interface.
ü Loads programs (such as word processing and spreadsheet programs) into the computer’s memory so that you can use them.
ü Coordinates how programs work with the computer’s hardware and other software.
ü Manages the way information is stored on and retrieved from disks.
In this lesson you will learn about the types of operating systems and the services they provide. Then you will learn about some of the enhancements you can make to your OS using utility software.

Functions of Operating System
Even the simplest operating system in a minicomputer or mainframe performs a number of resource management tasks or functions. These functions include job management, batch processing, on – line processing, data management, virtual storage and input / output management.

Job Management
Job Management software manages the jobs waiting to be processed. It recognizes the jobs, identifies their priorities, determines whether the appropriate main memory and secondary storage capability they require is available, and schedules and finally runs each job at the appropriate moment.

Batch Processing
System software is available to support the different methods of processing a job. With batch processing, the most basic method, data are accumulated and processed in groups. Payroll applications, for example are often processed this way. Once in every week, hourly records are grouped. and the payroll software is run.
Example: - Payroll preparation, Bill Preparation.

Online Processing or Real Time Processing
In online processing, data are processed instantaneously. For example, a sales person may need to find out whether a particular item requested by a customer is in stock for immediate shipment. Using an online system the request for information will be instantly acknowledged by the online software, and the appropriate steps will be taken to access the central database and return the requested information to the terminal from which the request was made. All of these steps take less than a few seconds, at the most. Most online operating systems have multi user and multitasking capabilities.
Example:- reservation systems. process control computers, where an alarm reaction time may be critical, is also real time system.

Data Management
In the process of managing the resources of the computer system, operating system software also manages the storage and retrieval of data. As the system software handles many of the details associated with the process, such details are not a primary concern for users of programmers writing application programs.

Virtual Storage
Operating systems also manages the allocation of main memory to specific job. Some operating systems have a feature called virtual storage. With this software it is possible to increase the capacity of main memory without actually increasing its size. This is accomplished by breaking a job into sequences of instructions, called pages or segments, and keeping only a few of these in main memory at a time; the reminder are kept on secondary storage devices. As a result, relatively large jobs can be processed by a CPU that in fact contains a relatively small memory.

Input/ Output Management
Operating systems also manage the input to and output from a computer system. This applies to the flow of data among computers, terminals, and other devices such as printers. Application programs use the operating system extensively to handle input and output devices as needed.

For large systems, the operating systems, the operating system has even greater responsibilities and powers. It is like a traffic policeman – it makes sure that the different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.

Types of Operating Systems
Operating systems can be organized into four major types: real-time, single- user/single-tasking, single-user/multitasking, and multi-user/multitasking. The following sections describe each type of OS.

Real-Time Operating Systems
A real-time operating system is a very fast, relatively small OS. Real-time OSs are often also embedded OSs, when they are built into the circuitry of a device and are not loaded from a disk drive. A real-time operating system is needed to run real-time applications; it may support multiple simultaneous tasks, or it may only support single-tasking. A real-time application is an application that responds to certain inputs extremely quickly—thousandths or millionths of a second (milliseconds or microseconds, respectively). Real-time applications are needed to run medical diagnostics equipment, life-support systems scientific instruments, and industrial systems.
Single-User/Single/Tasking Operating Systems
An operating system that allows a single user to perform just one task at a time is a single-user/single-tasking operating system. To a user, a “task” is a function such as printing a document, writing a file to disk, editing a file, or downloading a file from a network server. To the operating system, a task is a process, and small and simple OSs can only manage a single task at a time.
MS-DOS is one example of a single-tasking OS, and the Palm OS, used on the Palm handheld computers, is another (see Figure). Although such operating systems are limited by this characteristic, there is still a use for them, because they take up very little space on disk or in memory when they are running and do not require a powerful and expensive computer.

Single-User/Multitasking Operating Systems
A single-user/multitasking operating system is one that allows a single user to perform two or more functions at once. It takes a special operating system to keep two or more tasks running at once. The most commonly used personal computers usually run such OSs, including Microsoft Windows and the Macintosh Operating System (see Figure). The multitasking features of these OSs have greatly increased the productivity of people in a large variety of jobs because they can accomplish more in a shorter period of time. For instance, to an office worker, it is important to be able to send a large document to a printer and be able to do other work on his or her computer while it is being printed. It is also helpful for many types of workers to be able to have two or more programs open, to share the data between the two programs, and to be able to instantly switch between the two programs.
A disadvantage of a single-user/multitasking operating system is the increased size and complexity it needs to support multitasking, while keeping the related features users have come to expect, such as a graphical user interface, and the ability to share data between two or more open programs.
Multi-User/Multitasking Operating Systems
A multi-user/multitasking operating system is an operating system that allows multiple users to use programs that are simultaneously running on a single network server, a terminal server. This is not at all the same as connecting to a network server for the sake of accessing files and printers. As you will learn in Chapter, “Networks,” when a computer is connected to a server to access document files to edit, the client computer performs the processing work locally. Not so with a multi-user OS, which gives each user a complete environment, called a user session, on the server. Each user’s applications run within their user session on the server separate from all other user sessions. The software that makes this possible is called a terminal client. In a multi-user/multitasking operating system environment, all or most of the computing occurs at the server (see Figure). Examples of multi-user OSs include UNIX, VMS, and mainframe operating systems such as MVS.
The advantage of these operating systems is that they can be managed by simply making changes to one server, rather than to many desktop computers. They also allow the user to work with applications that require a more powerful computer than the user needs on the desktop to run the client. A disadvantage is that if the network connection to the server is broken, the user cannot do any work in the applications on the server.

Booting
Booting is a process in which your computer gets initialized. This process includes initializing all your hardware components in your computer and gets them to work together and to load your default operating system which will make your computer operational.
The System Boot Sequence consists of a series of events that the system performs when it is turned on (or rebooted with the reset switch). This always starts with the special boot program software that is in the system BIOS ROM on the motherboard. The BIOS performs several steps to test the system and make it ready before an operating system can be loaded. These steps are explained in detail here: The Master Boot Record and the System Boot Sequence.
Once the BIOS has completed its testing and system configuration, it begins the process of loading the operating system. The BIOS accomplishes this by searching the installed drives for a Master Boot Record in which is contained a boot code. Once found, the boot code is executed and the system is boot into the operating system. When looking for this Master Boot Record, the BIOS will search for boot devices (drives) in the order specified in the BIOS configuration settings controlling this aspect of the boot sequence. If it cannot find a boot device it will terminate with an error.
If the operating system is MS-DOS®, or any variant of Windows® other than Windows® NT or Windows® 2000, that starts out by booting the equivalent of DOS, then a specific operating system load sequence commences, which is referred to as the DOS Boot Process. If you are booting into Windows, additional steps are performed after the underlying MS-DOS® operating system has loaded.
The steps below takes you through the boot process from the hard disk. If you were to boot from a floppy disk, the steps would only differ slightly in the first few steps, as the floppy disk structures are slightly different. Floppies cannot be partitioned, and hence have no master boot record or partitions. This means that the master boot record issues are skipped.

MS-DOS boot process:
The BIOS, having completed its test and setup functions, loads the boot code found in the master boot record and then transfers control of the system to it. At that point, the master boot record code is executed. If the boot device is a floppy disk, the process skips to step 7 below.
The next step in the process is the master boot code examining the master partition table. It first must determine if there is an extended DOS partition, then it must determine if there is a bootable partition specified in the partition table.
If the master boot code locates an extended partition on the disk, it loads the extended partition table that describes the first logical volume in the extended partition. This extended partition table is examined to see if it points to another extended partition table. If it does, this second table is examined for information about the second logical volume in the extended partition. Logical volumes in the extended partition have their extended partition table chained together one to the next. This process continues until all of the extended partitions have been loaded and recognized by the system.
Once the extended partition information (if any) has been loaded, the boot code attempts to start the primary partition that is marked active, referred to as the boot partition. If no boot partitions are marked active, then the boot process will terminate with an error. The error message is often the same as that which occurs if the BIOS could not locate a boot device, generally shown on screen as "No boot device", but also can show up as "NO ROM BASIC - SYSTEM HALTED". If there is a primary partition marked active and there is an installed operating system, the boot code will boot it. The rest of the steps presume this example is of an MS- DOS primary partition.
At this stage, the master or volume boot sector is loaded into memory and tested, and the boot code that it contains is given control of the remainder of the boot process.
The boot code examines the disk structures to ensure that everything is correct. If not, the boot process will end in an error here.
During the next step, the boot code searches the root directory of the device being booted for the operating system files that contain the operating system. For MS-DOS, these are the files "IO.SYS", "MSDOS.SYS" and "COMMAND.COM".
If no operating system files are found, the boot program will display an error message similar to "Non-system disk or disk error - Replace and press any key when ready". Keep in mind that his message does not means that the system was never booted. It means that the BIOS examined the floppy disk for example and just rejected it because it couldn't boot an operating system. The volume boot code was indeed loaded and executed, as that is what posts the message when it can't find the operating system files.
In the final stages of the boot process, presuming that the operating system files are found, the boot program will load those operating system files into memory and transfer control to them. In MS-DOS, the first is IO.SYS and its code is executed. IO.SYS will then execute MSDOS.SYS. Then the more complete operating system code loads and initializes the rest of the operating system structures beginning with the command interpreter COMMAND.COM and then the execution of the CONFIG.SYS and AUTOEXEC.BAT files. At this point the operating system code itself has control of the computer.
If any of the Windows 95/98/ME versions were being started, the above would only be the beginning of the startup process. When MS-DOS starts in anticipation of loading these Windows versions, there are many more routines that are loaded and executed as part of the boot process, which includes such tasks such as reading the system registry, initializing hardware devices and starting the graphical user interface or operating system shell. We hope this has given you a better understanding of what occurs during the boot or startup process of your computer.

Types of Booting

The two main types of booting are:
1. A "cold boot" or a "hard reset," which occurrs when the computer (or micro processor system) is powered-up. The system has no history from the previous time it run, and needs to perform comprehensive initialization.
2. A "warm boot" or "soft reset," which occurrs when resetting the computer or micro processor system without interrupting its power supply. The continued supply of power allows certain initialization tasks to be skipped in the reboot, compared to the cold boot, and the re-initialization might complete sooner.

Configuring Devices
The operating system is also used to configure the devices connected to a computer system. Small program called device drivers (or just drivers) are used to communicate with peripheral devices, such as monitors, printers, and scanners. Most operating systems today include the drivers needed for the most commonly used peripheral devices. In addition, drivers often come on a disk or a CD packaged with the peripheral device, or they can be obtained from the manufacturers Web site. Most operating systems today look for new devices each time the PC boots and recognize new devices as they are connected to the PC. If a new device is found, the operating system will typically try to install the appropriate driver automatically in order to get the new hardware ready to use (see Figure) a feature called Plug and Play; Because USB and FireWire devices can be connected to a PC when the computer is running, those devices will be recognized and configured, as needed, whenever they are plugged into the PC.Once a device and its driver have been properly installed, they usually work fine. If the device driver file gets deleted or becomes corrupted, however, it will no longer work. Usually, the operating system detects this during the boot process and notifies the user that the driver needs to be reinstalled. The user can then reinstall the driver either by using the initial installation disk for that hardware or by downloading a new installation file from the manufacturer’s Web site, Device drivers also frequently need to be updated after you upgrade your operating system to a newer version. Some operating systems, such as Windows, have options to automatically check for operating system updates updated driver files—on a regular basis.

Providing a User Interface
When you work on a computer, you see and use a set of items on the screen. Taken together, these items are called the user interface. The two most common types of user interfaces are graphical and command line.

Command-Line Interfaces
Some older operating systems (such as Ms-DOS) and some current versions of UNIX and Linux feature a command-line interface, which uses typewritten commands—rather than graphical objects—to execute tasks. A command-line interface displays in character mode—using only equal-sized alphanumeric and other simple symbols. Users interact with a command-line interface by typing strings of characters at a prompt on the screen. In DOS, the prompt usually includes the identification for the active disk drive (a letter followed by a colon), a backslash (\), and a greater-than symbol (>), as in C:\>. As much as people prefer to work in a GUI, a command-line interface gives you a quick way to enter commands, and even now Windows has an optional command-line interface, called the Command Prompt (see Figure). This command prompt, however, is not DOS, and is most often used by administrators to run non-GUI programs for managing and troubleshooting Windows. In fact, any program that can be run in Windows can be launched from here, opening its own GUI window, if necessary.

Graphical User Interfaces
Most current operating systems, including all versions of Windows, the Macintosh operating system, OS/2, and some versions of UNIX and Linux, provide a graphical user interface (GUI, pronounced GOO-ee). Graphical user interfaces are so called because you use a mouse (or some other pointing device) to work with graphical objects such as windows, menus, icons, buttons, and other tools. These graphical tools all represent different types of commands; the GUI enables you to issue commands to the computer by using visual objects instead of typing commands. This is one of the key advantages of a graphical user interface; it frees you from memorizing and typing text commands.

Windows is one of several GUIs that use the desktop metaphor in which the background of the GUI is said to be a desktop on which you have your graphical tools and within which you can store your work. See Figure the Windows XP desktop. The small pictures on the desktop—called shortcuts—represent links to resources on the PC or network. Although shortcuts are often called icons, an icon actually is only the tiny graphic that represents an object, such as programs, folders, files, printers, and shortcuts. Using your mouse or other pointing device, you can move the pointer (a small graphic that moves in reaction to mouse movements) and choose (or activate) a shortcut, telling Windows you want to use the resource that the shortcut represents. For example, you can choose the Microsoft Word shortcut to launch that program. The items that appear on the desktop depend on the contents of the computer’s disks, the resources it can access, and the user’s preferences; therefore, any two Windows desktops can look different.
Certain elements always appear on the Windows desktop. As shown in Figure, the taskbar appears at the bottom of the Windows desktop; it is used to launch and manage programs. The Start button is a permanent feature of the taskbar; click it to open the Start menu. The Start menu contains shortcuts for launching programs and opening folders on a computer (see Figure). Shortcuts can be added to the desktop, the Start menu, and other areas. When you start a program in Windows, a button representing it appears on the taskbar.
You also can launch programs by clicking icons on the Quick Launch Bar, a special section at the left end of the taskbar where you can add icons for the purpose of quickly starting programs. Once you start a program, a button appears on the taskbar. When you have several programs on the desktop, one way in which you can switch between them is to click the program’s button on the taskbar.
When you right-click an object in Windows, a small menu usually appears containing the most common commands associated with that object. Depending on the version of Windows you are using, and whether you are using a specific application, this type of menu may be called a shortcut menu or a context menu. Either way, its function is the same: to provide quick access to commonly used commands related to the item you have right- clicked. Figure shows the short cut menu that appears when you right-click the desktop in Windows XP Professional.
When you launch a program, it is loaded into memory and begins to run. A running program may take up the whole screen, it may appear in a rectangular frame called a window, or it may appear only as a shortcut on the taskbar.

You access all the resources on your computer through windows. For example, you can view the contents of a disk in a window, run a program and edit a document in a window, view a Web page in a window, or change system settings in a window. A different window appears for each resource you want to use.

Above Figure shows Microsoft Word running in a window. Some menus and buttons, such as the ones shown here, appear in nearly every window you open. In the Windows GUI, programs share many of the same features, so you see a familiar interface no matter what program you are using. Among the common GUI features are the title bar, menu bar, toolbars, scroll bars, and various buttons. The title bar identifies the windows’ contents and it also contains the Minimize, Restore, and Close buttons, which let you hide the window, resize it, or close it altogether. The menu bar provides lists of commands and options for this specific program. Tool bars contain buttons that let you issue commands quickly. Scroll bars let you view parts of the program or file that do not fit in the window.
A graphical operating system lets you have multiple programs and resources running at the same time, but you can work in only one window at a time. The window that is currently in use is called the active window; its title bar appears in a deeper color shade than that of other visible open windows, and its taskbar button appears high lighted or “pressed in.” Unless all open windows are arranged side by side, the active window will appear on top of any inactive windows. You must select the window you want to use before you can access its contents. The process of moving from one open window to another is called task switching. You can either click an open window to activate it or click an open program’s taskbar button to activate its window.
You initiate many tasks by clicking icons and toolbar buttons, but you also can perform tasks by choosing commands from lists called menus. In most program windows, you open menus from a horizontal list called the menu bar. As shown in Figure, many programs feature a File menu, which typically contains commands for opening, closing, saving, and printing files. To execute or run one of the menu commands, you click it. In many cases, you can issue menu commands by using keyboard shortcuts instead of the mouse.



Dialog boxes are special-purpose windows that appear when the OS or application needs to give you some status and possible choice of actions or you need to tell a program (or the operating system) what to do next. A dialog box is so named because it conducts a “dialog” with you as it seeks the information it needs to perform a task. A dialog box can even have more than one page, in which case the pages are made available through tabs and look like a stack of tabbed pages. Figure shows a dialog box from Microsoft Word and describes some of the most common dialog box features.

Sharing Information
Many types of applications let you move chunks of data from one place to another. For example, you may want to copy a chart from a spreadsheet program and place the copy in a document in a word processing program (see Figure). Some operating systems accomplish this feat with a feature known as the Clipboard. The Clipboard is a temporary holding space (in the computer’s memory) for data that is being copied or moved. The Clipboard is available for use by applications running under the operating system. For example, if you want to move a paragraph in a word processor document, select the paragraph, then choose the cut command; data is removed from the document and placed on the Clipboard. (If you want to leave the original data in place, you can use the copy command; a copy is made of the data, and it is stored on the Clipboard but is not removed from the document.) After placing the insertion point in the document where you want to place the paragraph, you choose the Paste command; the data on the Clipboard is then placed into the document.
The Clipboard also can he used to move data from one document to another. For example, you can copy an address from one letter to another and thereby avoid reeking the address. The real versatility of the Clipboard, however, stems from the fact that it is actually a part of the operating system and not a particular application. As a result, you can use the Clipboard to move data from one program to another.




Running Programs
The operating system provides a consistent interface between application programs and the user. It is also the interface between those programs and other computer resources such as memory, a printer; or another program. Programmers write computer programs with built-in instructions—called system calls request services from the operating system. They are known as “calls” because the program has to call on the operating system to provide some information or service.
For example, when you want your word processing program to retrieve a file, you use the Open dialog box to list the files in the folder that you specify (see Figure). To provide the list, the program calls on the operating system. The OS goes through the same process to build a list of files whether it receives its instructions from you (via the desktop) or from an application. The difference is that when the request comes from an application, the operating system sends the results of its work back to the application rather than to the desktop.


Some other services that an operating system provides to programs, in addition to listing files, include
ü Saving the contents of files to a disk.
ü Reading the contents of a file from disk into memory.
ü Sending a document to the printer and activating the printer.
ü Providing resources that let you copy or move data from one document to another, or from one program to another.
ü Allocating RAM among the running programs.
ü Recognizing keystrokes or mouse clicks and displaying characters or graphics on the screen.
The versatility of the Clipboard has been extended further with a feature known in Windows as OLE, which stands for Object Linking and Embedding. A simple cut and paste between applications results in object embedding. The data, which is known as an object in programming terms, is embedded in a new type of document. It retains the formatting that was applied to it in the original application but its relationship with the original file is destroyed; that is, it is simply part of the new tile. Furthermore, the data may be of a type that the open application cannot change. Therefore, if you want to edit embedded data, simply double-click the embedded object, and the original application that created the data is opened to allow editing of the embedded data.
Object linking adds another layer to the relationship: The data that is copied to and from the Clipboard retains a link to the original document so that a change in the original document also appears in the linked data. For example, suppose that the spreadsheet and memo shown in Figure 6A. 13 are generated quarterly. They always contain the same chart updated with the most recent numbers. With object linking, when the numbers in the spreadsheet are changed, the chart in the report will automatically reflect the new figures. Of course, object linking is not automatic; you need to use special commands in your applications to create the link.
Managing Hardware
When programs run, they need to use the computer’s memory, monitor, disk drives, and other devices, such as a printer. The operating system is the intermediary between programs and hardware. In a computer network, the operating system also mediates between your computer and other devices on the network.
Buffering and Spooling
Some input and output devices are exceedingly slow, compared to today’s CPUs. If the CPU had to wait for these slower devices to finish their work, the computer system would face a horrendous bottleneck. For example, suppose a user just sent a 50-page document to the printer. Assuming the printer can output 10 pages per minute, it would take 5 minutes for the document to finish printing. If the CPU had to wait for the print job to be completed before performing other tasks, the PC would be fled up for 5 minutes-
To avoid this problem, most operating systems use two techniques—buffering and spooling. A buffer is an area in RAM or on the hard drive designated to hold input and output on her way in or out of the system. For instance, a keyboard buffer stores certain - - number of characters as they are entered via the keyboard, and a print buffer stores documents that are waiting to be printed. The process of placing items in a buffer so they can he retrieved by the appropriate device when needed is called spooling. The most common use of spooling and buffering is for print jobs. It allows multiple documents to be sent to the printer at one time, and they will print, one after the other, in the background while the computer mid user is performing tasks. The documents waiting to be printed are said to be in a queue, which designates the order the documents will he printed.
Processing Interrupts
The operating system responds to requests to use memory and other devices, keeps track of which programs have access to which devices, and coordinates everything the hardware does so that various activities do not overlap causing the computer to become confused and stop working. The operating system uses interrupt requests (IRQs) to help the CPU coordinate processes. For example, Figure shows what happens if you tell the operating system to list the files in a folder.
Working with Device Driver
In addition to using interrupts, the operating system often provides programs for working with special devices such as printers. These programs are called drivers because they allow the operating system and other programs to activate and use that is, “drive” the hardware device. Most new software you buy will work with your printer, monitor, and other equipment without requiring you to install any special drivers.
Enhancing an OS with Utility Software
Operating systems are designed to let you do most of the tasks you normally would want to do with a computer, such as managing files, loading programs, printing documents, and so on. But software developers are constantly creating new programs—called utilities—that enhance or extend the operating system’s capabilities, or that simply offer new features not provided by the operating system itself. As an operating system is improved and updated, the functionality of popular utilities is included with subsequent releases of the OS. There are thousands of different utility programs, and you can find many on the Internet—some free and some at a price ranging from very inexpensive to hundreds of dollars.
While it is difficult to give a definitive list of utility software categories, the most common types that ordinary people use are disk and file management, Internet security, and OS customization tools. To complicate matters further, there are many packaged utility suites that combine two or more utilities into one bundle. The following sections describe a small selection of popular utilities.
Backup Utilities
For safekeeping, a backup utility can help you copy large groups of files from your hard disk to another storage medium, such as tape or a CD-R disc. Many newer operating systems feature built-in backup utilities (see Figure), but feature-rich backup software is available from other sources. These utilities not only help you transfer files to a backup medium, they also help organize the files, update backups, and restore backups to disk in case of data loss.
Antivirus
A virus is a parasitic program that can delete or scramble files or replicate itself until the host disk is full. As you will learn in “Computing Keynotes: Viruses,” computer viruses can be transmitted in numerous ways, and users should be especially vigilant when downloading files over the Internet or reusing old diskettes that may be infected. An antivirus utility can examine the contents of a disk or RAM for hidden viruses and files that may act as hosts for virus code. Effective antivirus products not only detect and remove viruses; they also help you recover data that has been lost because of a virus.
Firewall
Your ISP and most corporations employ specialized computers on their Internet connections that are dedicated to examining and blocking traffic coming from and going to the Internet. Such a computer is called a firewall, and manufacturers such as Cisco, 3COM, and others offer these products at a very high price. These firewalls also require highly trained people to manage them. If you work in a corporation where a firewall is protecting the corporate network, leave the firewall function to the experts. At home, however, you will want to be sure to use either a smaller, less-expensive hardware firewall or install a software firewall utility on any computer directly connected to the Internet. Windows XP comes with a simple firewall that you can optionally turn on through the Properties dialog of each network connection. There are many third-party firewall programs, such as Kerio Winroute Pro.
Intrusion Detection
While a firewall offers protection from predictable intrusion, intrusion detection software reveals the types of attacks a firewall is thwarting, creating logs of the attempts and (depending on how you configure it) notifying you of certain types of intrusion attempts. In the competitive utility software field, intrusion detection is often added as a feature to firewall or bundled Internet security programs.
Screen Savers
Screen savers are popular utilities, although they serve little purpose other than to hide what would otherwise be displayed on the screen. A screen saver automatically appears when a keyboard or pointing device has not been used for a specified period of time. Screen savers display a moving image on the screen and were originally created to prevent displayed images from “burning” into the monitor. Today’s monitors do not suffer from this problem, but screen savers remain a popular utility because they can add personality to the user’s system.


Define Operating System

Explain the purpose of Operating System in Detail

Explain the function of operating system in detail

Explain different types of Operating system.

Explain the Difference between Character User Interface and Character User Interface.

What is booting? Name and explain two types of Booting

Write Short note on Managing Hardware

Define spooling

Define Utilities

What is Virus?

What is the use of Antivirus?

Write Short note on Screen Saver

Write short note on Firewall

What is the disadvantage of single-user/multitasking operating system?

Explain MS-DOS Process

The small pictures on the desktop called shortcuts represent links to resources on the PC or network

Icons are programs, folders, files, printers and shortcuts.

Start Button is a permanent feature of the taskbar.

Quick Launch Bar is a special section at the left end of the taskbar where you can add icons for the purpose of quickly starting programs.

Dialog Boxes are special purpose windows that appear when the OS or application needs to give you some status and possible choice of actions.

The Clipboard can be used to move data from one document to another.

A buffer is an area in RAM or on the hard drive designated to hold input and output on her way in or out of the system.

Clipboard retains a link to the original document so that a change in the original document also appears in the linked data.

A single-user/multitasking operating system is one that allows a single user to perform two or more functions at once.

A multi-user/multitasking operating system is an operating system that allows multiple users to use programs that are simultaneously running on a single network server, a terminal server.

The System Boot Sequence consists of a series of events that the system performs when it is turned on

The BIOS performs several steps to test the system and make it ready before an operating system can be loaded.

The operating system uses interrupt requests to help the CPU coordinate processes

Real-time applications are needed to run medical diagnostics equipment, life-support systems scientific instruments, and industrial systems.
The two most common types of user interfaces are graphical and command line.

The data, which is known as an object in programming terms, is embedded in a new type of document.