Chapter 7: Operating Systems and Utility programs
OBJECTIVES
After completing this chapter, you will be able to:
1. Identify the types of system software
2. Describe the functions of an operating system
3. Explain the purpose of the utilities included with most operating systems
4. Summarize the features of several stand-alone operating systems
5. Identify devices that use embedded operating systems
6. Explain the purpose of several stand-alone utility programs
SYSTEM SOFTWARE
OPERATING SYSTEM FUNCTIONS
Starting a Computer
Providing a User Interface
Managing Programs
Managing Memory
Scheduling Jobs
Configuring Devices
Establishing an Internet Connection
Monitoring Performance
Providing File Management and Other Utilities
Controlling a Network
Administering Security
PROGRAMS
File Manager
Image Viewer
Personal Firewall
Uninstaller
Disk Scanner
Disk Defragmenter
Diagnostic Utility
Backup Utility
Screen Saver
TYPES OF OPERATING SYSTEMS
DOS
Windows XP
Mac OS X
UNIX
Linux
NETWORK OPERATING SYSTEMS EMBEDDED OPERATING SYSTEMS
Antivirus Programs
Spyware Removers
Internet Filters
File Compression
File Conversion
CD/DVD Burning
Personal Computer Maintenance
Red Hat
Symbian
Alan Kay
Linus Torvalds
When you purchase a personal computer, it usually has system software installed on its hard disk System software consists of the programs that control or maintain the operations of the computer and its devices. System software serves as the interface between the user, the application software, and the computer’s hardware.
Two types of system software are operating systems and utility programs. This chapter discusses the operating system and its functions, as well as several types of utility programs for personal computers.
An operating system (OS) is a set of programs containing instructions that coordinate all the activities among computer hardware resources. Most operating systems perform similar functions that include starting a computer, providing a user interface, managing programs, managing memory, scheduling jobs, configuring devices, establishing an Internet connection, monitoring performance, and providing file management utilities. Some operating systems also allow users to control a network and administer security (Figure 7-1).
In most cases, the operating system is installed and resides on the computer’s hard disk. On handheld computers and many mobile devices, however, the operating system may reside on a ROM chip.
Different sizes of computers typically use different operating systems. For example, a mainframe computer does not use the same operating system as a personal computer. Even the same types of computers, such as desktop computers, may not use the same operating system. Furthermore, the application software designed for a specific operating system may not run when using another operating system. For example, PCs often use Windows XP, and iMacs use Mac OS X. When pur chasing application software, you must ensure that it works with the operating system installed on your computer.
The operating system that a computer uses sometimes is called the platform. On purchased application software, the package identifies the required platform (operating system). A cross- platform program is one that has multiple versions, and each version runs identically on multiple operating systems.
Many different operating systems exist; however, most operating systems provide similar functions. The following sections discuss functions common to most operating systems. The operating system handles many of these functions automatically, without requiring any instruction from a user.
Booting is the process of starting or restarting a computer. When turning on a computer that has been powered off completely, you are performing a cold boot. A warm boot, by contrast, is the process of using the operating system to restart a computer. With Windows XP, for example, you can perform a warm boot by selecting a button in a dialog box (Figure 7-2). Some computers have a reset button that when pressed restarts the computer as if it had been powered off.
When you install new software, often an on-screen prompt instructs you to restart the computer. In this case, a warm boot is appropriate.
Each time you boot a computer, the kernel and other frequently used operating system instructions are loaded, or copied, from the hard disk (storage) into the computer’s memory (RAM). The kernel is the core of an operating system that manages memory and devices, maintains the computer’s clock, starts applications, and assigns the computer’s resources, such as devices, programs, data, and information. The kernel is memory resident, which means it remains in memory while the computer is running. Other parts of the operating system are nonresident, that is, these instructions remain on the hard disk until they are needed.
When you boot a computer, a series of messages may be displayed on the screen. The actual information displayed varies depending on the make and type of the computer and the equipment installed. The boot process, however, is similar for large and small computers.
FIGURE 7-2 To reboot a running computer, click the Restart button in the Turn off computer dialog box.
When I am finished using the computer, can I simply turn it off?
No! You must use the operating system’s shut-down procedure so various processes are closed in sequence and items in memory released properly. Depending on the computer, several shut-down options exist. The Turn Off command removes power from the computer. Restart does a warm boot. Hibernate saves all documents in memory and then turns off the computer. Stand By places the entire computer in a low-power state but does not turn it off. With the Hibernate and Stand By options, the next time you resume work on the computer, the desktop is restored to exactly how you left it. For more information, visit scsite.com/dcf2e/ch7/faq and then click Shut-Down Options.
You interact with software through its user interface. That is, a user interface controls how you enter data and instructions and how information is displayed on the screen. Two types of user interfaces are command-line and graphical. Operating systems sometimes use a combination of these interfaces to define how a user interacts with a computer.
COMMAND-LINE INTERFACE
To configure devices, manage system resources, and troubleshoot network connections, network administrators and other advanced users work with a command- line interface. In a command-line interface, a user types commands or presses special keys on the keyboard to enter data and instructions (Figure 7-3a). Command-line interfaces often are difficult to use because they require exact spelling, grammar, and punctuation. Minor errors, such as a missing period, generate an error message. Command-line interfaces, however, give a user more control to manage detailed settings.
GRAPHICAL USER INTERFACE
Most users today work with a graphical user interface. With a graphical user interface (GUI), you interact with menus and visual images such as buttons and other graphical objects to issue commands (Figure 7-3b). Many current GUI operating systems incorporate features similar to those of a Web browser.
FIGURE 7-3a (command-line interface)
Some operating systems support a single user and only one running program at a time. Others support thousands of users running multiple programs. How an operating system handles programs directly affects your productivity.
A single user/single tasking operating system allows only one user to run one program at a time. PDAs, smart phones, and other small computing devices often use a single user/single tasking operating system.
A single user/multitasking operating system allows a single user to work on two or more programs that reside in memory at the same time. Users today typically run multiple programs concurrently. It is common to have an e-mail program and Web browser open at all times, while working with application programs such as word processing or graphics.
FIGURE 7-3 Examples of command-line and graphical user interfaces.
When a computer is running multiple programs concurrently, one program is in the foreground and the others are in the background. The one in the foreground is the active program, that is, the one you currently are using. The other programs running but not in use are in the background. In Figure 7-4, the PowerPoint program, which is showing a slide show, is in the foreground, and three other programs are running in the background (Paint Shop Pro, Encarta Encyclopedia, and iTunes).
FIGURE 7.4 The foreground program, PowerPoint, is displayed on the desktop. The other programs (Paint Shop Pro, Encarta Encyclopedia, and iTunes) are in the background.
The foreground program typically is displayed on the desktop but the background programs often are partially or completely hidden behind the foreground program. You easily can switch between foreground and background programs. To make a program active (in the foreground) in Windows XP, click its program button on the taskbar. This causes the operating system to place all other programs in the background.
A multiuser operating system enables two or more users to run programs simultaneously. Networks, midrange servers, mainframes, and supercomputers allow hundreds to thousands of users to connect at the same time, and thus are multiuser.
A multiprocessing operating system supports two or more processors running programs at the same time. Multiprocessing involves the coordinated processing of programs by more than one processor. Multiprocessing increases a computer’s processing speed.
A computer with separate processors also can serve as a fault-tolerant computer. A fault-tolerant computer continues to operate when one of its components fails, ensuring that no data is lost. Fault-tolerant computers have duplicate components such as processors, memory and disk drives. If any one of these components fails, the computer switches to the duplicate component and continues to operate. Airline reservation systems, communications networks, automated teller machines, and other systems that must be operational at all times use fault-tolerant computers.
The purpose of memory management is to optimize the use of random access memory (RAM). RAM consists of one or more chips on the motherboard that hold items such as data and instruc tions while the processor interprets and executes them. The operating system allocates, or assigns, data and instructions to an area of memory while they are being processed. Then, it carefully monitors the contents of memory. Finally, the operating system releases these items from being monitored in memory when the processor no longer requires them.
Virtual memory is a concept in which the operating system allocates a portion of a storage medium, usually the hard disk, to function as additional RAM. As you interact with a program, part of it may be in physical RAM, while the rest of the program is on the hard disk as virtual memory. Because virtual memory is slower than RAM, users may notice the computer slowing down while it uses virtual memory.
The operating system uses an area of the hard disk for virtual memory, in which it swaps (exchanges) data, information, and instructions between memory and storage. The technique of swapping items between memory and storage is called paging. When an operating system spends much of its time paging, instead of executing application software, it is said to be thrash ing. If application software, such as a Web browser, has stopped responding and the hard disk’s LED blinks repeatedly, the operating system probably is thrashing.
The operating system determines the order in which jobs are processed. A job is an operation the processor manages. Jobs include receiving data from an input device, processing instructions, sending information to an output device, and transferring items from storage to memory and from memory to storage.
A multiuser operating system does not always process jobs on a first-come, first-served basis. Sometimes, one user may have a higher priority than other users. In this case, the operating sys tem adjusts the schedule of jobs.
Sometimes, a device already may be busy processing one job when it receives a second job. This occurs because the processor operates at a much faster rate of speed than peripheral devices. For example, if the processor sends five print jobs to a printer, the printer can print only one doc ument at a time.
While waiting for devices to become idle, the operating system places items in buffers. A buffer is a segment of memory or storage in which items are placed while waiting to be transferred from an input device or to an output device.
The operating system commonly uses buffers with print jobs. This process, called spooling, sends print jobs to a buffer instead of sending them immediately to the printer. The buffer holds the information waiting to print while the printer prints from the buffer at its own rate of speed. By spooling print jobs to a buffer, the processor can continue interpreting and executing instructions while the printer prints. This allows users to work on the computer for other tasks while a printer is printing. Multiple print jobs line up in a queue (pronounced Q) in the buffer. A pro gram, called a print spooler, intercepts print jobs from the operating system and places them in the queue (Figure 7-5).
A driver is a small program that tells the operating system how to communicate with a specific device. Each device on a computer, such as the mouse, keyboard, monitor, printer, and scanner, has its own specialized set of commands and thus requires its own specific driver. When you boot a computer, the operating system loads each device’s driver.
If you attach a new device to a computer, such as a printer or scanner, its driver must be installed before you can use the device. For many devices, the computer’s operating system may include the necessary drivers. If it does not, you can install the drivers from the CD or disk pro vided with the purchased device.
Today, many devices and operating systems support Plug and Play. Plug and Play means the operating system automatically configures new devices as you install them. With Plug and Play, a user can plug in a device, turn on the computer, and then use the device without having to configure the system manually.
Operating systems typically provide a means to establish Internet connections. For example, Windows XP includes a New Connection Wizard that guides users through the process of setting up a connection between a computer and an Internet service provider (Figure 7-6).
Some operating systems also include a Web browser and an e-mail program, enabling you to begin using the Web and communicate with others as soon as you set up the Internet connection. Some also include a built-in firewall to protect computers from unauthorized intrusions.
FIGURE 7-5 Spooling increases both processor and printer efficiency by placing print jobs in a buffer on disk before they are printed. This figure illustrates three jobs in the queue with one job printing.
For more information, visit scsite.com/dcf2e/ ch7/weblink and then click Plug and Play.
FIGURE 7-6 To display the New Connection Wizard in Windows XP, click the Start button, point to All Programs, point to Accessories, point to Communications, and then click New Connection Wizard on the Communications submenu.
Operating systems typically contain a performance monitor. A performance monitor is a program that assesses and reports information about various computer resources and devices.
The information in performance reports helps users and administrators identify a problem with resources so they can try to resolve any problems. If a computer is running extremely slow, for example, the performance monitor may determine that the computer’s memory is being used to its maximum. Thus, you might consider installing additional memory in the computer.
Operating systems often provide users with the capability of managing files, viewing images, securing a computer from unauthorized access, uninstalling programs, scanning disks, defragmenting disks, diagnosing problems, backing up files and disks, and setting up screen savers. A later section in the chapter discusses these utilities in depth. Read At Issue 7-1 for a related discussion.
Some operating systems are network operating systems. A network operating system, or network OS, is an operating system that organizes and coordinates how multiple users access and share resources on a network. Resources include hardware, software, data, and information. For example, a network OS allows multiple users to share a printer, Internet access, files, and programs.
Some operating systems have network features built into them. In other cases, the network OS is a set of programs separate from the operating system on the client computers that access the net work. When not connected to the network, the client computers use their own operating system. When connected to the network, the network OS may assume some of the operating system functions.
The network administrator, the person overseeing network oper ations, uses the network OS to add and remove users, computers, and other devices to and from the network. The network administrator also uses the network operating system to install software and administer network security.
AT Issue Who Is Responsible for Operating System Security?
A few years ago, the Sasser worm infected almost one million computers in the stretch of a weekend. Surprisingly, most computer users already had the necessary means to stop this worm before it even got started. The Windows XP operating system comes equipped with built-in firewall protection, but, by default, the feature was turned off. Microsoft later released a service pack, or update, for the operating system in which the feature was turned on by default. Most operating system manufacturers allow users automatically to download and install up-to-date security patches. It is up to the users to make use of this service properly and make certain that their operating system software is up-to-date. Sometimes, as was the case with the Sasser worm, the updates come too late. Often, users are not technically savvy enough to keep up with the security updates or to configure a network connection with a firewall properly. Who should be responsible for operating system security? Why? Should operating system manufacturers be required to send security updates to computer users? Why or why not? Should users be required to take responsibility for worms and viruses that they spread to others due to lax security? Why or why not?
The network administrator uses the network OS to establish permissions to resources. These permissions define who can access certain resources and when they can access those resources.
For each user, the network administrator establishes a user account, which enables a user to access, or log on to, a computer or a network. Each user account typically consists of a user name and password (Figure 7-7). A user name, or user ID, is a unique combination of characters, such as letters of the alphabet or numbers that identifies one specific user. Many users select a combination of their first and last names as their user name. A user named Henry West might choose H West as his user name.
A password is a private combination of characters associated with the user name that allows access to certain computer resources. Some operating systems allow the network administrator to assign passwords to files and commands, restricting access to only authorized users.
To prevent unauthorized users from accessing computer resources, keep your password confidential. While entering your password, most computers hide the actual password characters by displaying some other characters, such as asterisks (*) or dots. After entering a user name and password, the operating system compares the user’s entry with a list of authorized user names and passwords. If the entry matches the user name and password kept on file, the operating system grants the user access. If the entry does not match, the operating system denies access to the user.
The operating system records successful and unsuccessful logon attempts in a file. This allows the network administrator to review who is using or attempting to use the computer. Network administrators also use these files to monitor computer usage.
To protect sensitive data and information as it travels over the network, a network operating system may encrypt it. Encryption is the process of encoding data and information into an unreadable form. Network administrators can set up a network to encrypt data as it travels over the network to prevent unauthorized users from reading the data. When an authorized user attempts to read the data, it automatically is decrypted, or converted back into a readable form.
Test your knowledge of pages 250 through 258 in QuizYourself 7-1.
QUIZ YOURSELF 7
Instructions: Find the true statement below. Then, rewrite the remaining false statements so they are true.
1. A buffer is a small program that tells the operating system how to communicate with a specific device.
2. A warm boot is the process of using the
4. The program you currently are using is in the background, and the other programs running but not in use are in the foreground.
5. Two types of system software are operating systems and application programs.
Quiz Yourself Online: To further check your knowledge of system software and functions common to most operating systems, visit scsite.com/dcf2e/ch7/quiz and then click Objectives 1 — 2.
FIGURE 7.7 Most multiuser operating systems allow each user to log on, which is the process of entering a user name and a password into the computer.
Choose a password that no one could guess. Do not use any part of your first or last name, your spouse’s or child’s name, telephone number, street address, license plate number, Social Security number, and so on. Be sure your password is at least six characters long, mixed with letters and numbers. For more information, visit scsite.com/dcf2e/ch7/faq and then click Passwords.
A utility program, also called a utility, is a type of system software that allows a user to perform maintenance-type tasks, usually related to managing a computer, its devices, or its programs. Most operating systems include several built-in utility programs (Figure 7-8). Users often buy stand-alone utilities, however, because they offer improvements over those included with the operating system. Utility programs included with most opera ting systems provide the following functions: managing files, viewing images, securing a computer from unauthorized access, uninstalling programs, scanning disks, defragmenting disks, diagnosing problems, backing up files and disks, and setting up screen savers. The following sections briefly discuss each of these utilities.
A file manager is a utility that performs functions related to file management. Some of the file management functions that a file manager performs are for matting and copying disks; displaying a list of files on a storage medium (Figure 7-9); checking the amount of used or free space on a storage medium; and organizing, copying, renaming, deleting, moving, and sorting files.
Formatting is the process of preparing a disk for reading and writing. Most floppy and hard disk manufacturers preformat their disks. If you must format a floppy disk or other media, you can do so using the file manager.
An image viewer is a utility that allows users to display, copy, and print the contents of a graphics file. With an image viewer, users can see images without having to open them in a paint or image-editing program. Windows XP includes an image viewer called Windows Picture and Fax Viewer (Figure 7-10). To display a file in this image viewer, simply double-click the thumbnail of the image in the file manager, such as the one shown in Figure 7-9.
FIGURE 7.8 Many utilities available in Windows XP are accessible through the Accessories and System Tools submenus.
FIGURE 7.9 With Windows Explorer, which is the file manager included with Windows XP, users can display a list of graphics files on a disk. In this case, thumbnails of the files are displayed.
FIGURE 7-10 Windows Picture and Fax Viewer allows users to see the contents of a graphics file.
A personal firewall is a utility that detects and protects a personal computer from unauthorized intrusions. Personal firewalls constantly monitor all transmissions to and from a computer.
When connected to the Internet, your computer is vulnerable to attacks from a hacker. A hacker is someone who tries to access a computer or network illegally. Users with broadband Internet connections, such as through DSL and Internet cable television service, are even more susceptible than those with dial-up access because the Internet connection is always on.
The latest update to Windows XP automatically enables the built-in personal firewall upon installation. This firewall, called Windows Firewall, is easy to access and configure (Figure 7-11). If your operating system does not include a personal firewall or you want additional protection, you can purchase a stand-alone personal firewall utility or a hardware firewall, which is a device such as a router that has a built-in firewall.
An uninstaller is a utility that removes a program, as well as any associated entries in the system files. When you install a program, the operating system records the information it uses to run the software in the system files. The uninstaller deletes files and folders from the hard disk, as well as removes program entries from the system files.
A disk scanner is a utility that (1) detects and corrects both physical and logical problems on a hard disk and (2) searches for and removes unnecessary files. A physical disk problem is a problem with the media such as a scratch on the surface of the disk. A logical disk problem is a problem with the data, such as a corrupt file.
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