Monday, May 30, 2011
Operating Systems and Utility Programs
Chapter 8: Operating Systems and Utility Programs
Describe The Two Types Of SoftwareTwo types of software are application software and system software. Application software consists of programs that perform specific tasks for users, such as a word processing program, e-mail program, or Web browser. System software consists of the programs that control the operations of a computer and its devices. The two types of system software are operating systems and utility programs. An operating system (OS) is a set of programs containing instructions that coordinate all the activities among computer hardware devices. A utility program performs a specific task, usually related to managing a computer, its devices, or its programs.
Booting is the process of starting or restarting a computer. When you turn on the computer, the power supply sends an electrical signal to devices located in the system unit. The processor chip resets itself and looks for the ROM chip that contains the BIOS (basic input/output system), which is firmware that holds the startup instructions. The BIOS executes the power-on self test (POST) to make sure hardware is connected properly and operating correctly. The POST results are compared with data in a CMOS chip on the motherboard. If the POST completes successfully, the BIOS searches for specific operating system files calledsystem files. Once located, the boot drive (the drive from which your personal computer starts), loads the system files from storage (the hard disk – usually drive C) into memory (RAM) and executes them. Next, the kernel of the operating system loads into memory and takes control of the computer. The operating system loads configuration information. In Windows XP, the registry consists of several file that contain the system configuration information. When complete, the Windows XP desktop and icons display, and programs in the StartUp folder are executed.
A user interface controls how you enter data and instructions and how information displays on the screen. Two types of user interfaces are command-line and graphical. With a command-line interface, you type keywords or press special keys to enter data or instructions. A graphical user interface (GUI) allows you to use menus and visual images such as icons, buttons, and other graphical objects to issue commands. A menu is a set of commands from which you can choose. Anicon is a small image that represents a program, an instruction, a file, or some other object.
Most operating systems perform similar functions that include managing programs, managing memory, scheduling jobs, configuring devices, accessing the Web, monitoring performance, providing housekeeping services, and administering security. Managing programs directly affects your productivity. A single user/single tasking operating system allows only one user to run one program at a time. A multitasking operating system allows a single user to work on two or more applications that reside in memory at the same time. A multi-user operating system enables two or more users to run a program simultaneously.
A multiprocessing operating system can support two or more CPUs running programs at the same time. Managing memory involves assigning items to an area of memory while they are being processed. The purpose of memory management is to optimize use of random access memory (RAM). With virtual memory (VM), the operating system optimizes memory by allocating a portion of a storage medium, usually the hard disk, to function as additional RAM. Scheduling jobs(operations the processor manages) involves determining the order in which jobs are processed.
Spooling increases efficiency by placing print jobs in a buffer (an area of memory or storage where data resides while waiting to be transferred) until the printer is ready, freeing the processor for other tasks. Configuring devices establishes communication with each device in the computer. A device driver is a small program that tells the operating system how to communicate with a device. Accessing the Web may entail including a Web browser and e-mail program in the operating system. Monitoring performance helps to identify and solve system problems.A performance monitor is a program that assesses and reports information about various system resources and devices. Providing housekeeping services entails performing storage and file management functions. A file manager performs such functions as formatting and copying disks; listing the files on a storage medium; checking the amount of used and unused space on a storage medium; organizing, copying, deleting, moving, and sorting files; and creating shortcuts (icons on the desktop that run a program when clicked).
Administering security involves establishing user accounts on a network. Each account typically requires a user name and a password to log on, or access, the network.
A stand-alone operating system is a complete operating system that works on a desktop or notebook computer. A network operating system (also callednetwork OS or NOS) is an operating system that supports a network. A network is a collection of computers and devices connected together via communications media and devices such as cables, telephone lines, and modems. In some networks, the server is the computer that controls access to the hardware and software on a network and provides a centralized storage area. The other computers on the network, called clients, rely on the server(s) for resources.
Stand-alone operating systems include DOS, Windows 3.x, Windows 95, Windows NT Workstation, Windows 98, Windows 2000 Professional, Windows Millennium Edition, Windows XP Home Edition, Windows XP Professional Edition, Mac OS, OS/2 Warp Client, UNIX, and Linux. UNIX and Linux also function as network operating systems.
DOS (Disk Operating System) refers to several single user, command-line and menu-driven operating systems developed in the early 1980s for personal computers. Windows 3.x refers to early operating environments that, although not operating systems, provided a graphical user interface to work in combination with DOS and simplify its use. Windows 95 is a true multitasking operating system – not an operating environment – with an improved graphical interface. Windows NT Workstation is a client operating system that can connect to a Windows NT Server. Developed as an upgrade to Windows 95, the Windows 98 operating system is easier to use and more integrated with the Internet. Windows 98 includes Microsoft Internet Explorer, a popular Web browser, Windows Explorer, a file manager, and an Active Desktop™ that works similarly to Web links. Windows 2000 Professional is a complete, reliable multitasking client operating system for business desktop and business notebook computers. Windows Millennium Edition is an operating system that has features specifically for the home user.Windows XP is Microsoft’s fastest, most reliable Windows operating system, providing quicker startup, better performance, and a new, simplified visual look.Windows XP Home Edition is an upgrade to Windows Millennium Edition, while Windows XP Professional Edition is an upgrade to Windows 2000 Professional.The Mac OS, the latest version of the Macintosh operating system (the first commercially successful graphical user interface), is a multitasking operating system available only on Apple computers. OS/2 Warp Client is IBM’s GUI multitasking client operating system that supports networking, Java, the Internet, and speech recognition.
Network operating systems include NetWare, Windows NT Server, Windows 2000 Server, Windows .NET Server, OS/2 Warp Server for E-business, UNIX, Linux, and Solaris™. Novell’s NetWare is a widely used network operating system designed for client/server networks. Windows NT Server is the operating system used by servers in the Windows NT client/server network environment. The Windows 2000 Server family consists of three products: Windows 2000 Server (for the typical business network), Windows 2000 Advanced Server (for e-commerce applications), and Windows 2000 Database server (for demanding, large-scale applications). Windows .NET Server is an upgrade to Windows 2000 Server. The Windows .NET Server family includes four products:Windows .NET Standard Server (for the typical small- to medium-sized business network), Windows .NET Enterprise Server (for medium- to large-sized businesses, including those with e-commerce applications), Windows .NET Datacenter (for business with huge volumes of transactions and large-scale databases), and Windows .NET Web Server (for Web server and Web hosting businesses).
OS/2 Warp Server for E-business is IBM’s network operating system designed for all sizes of business.
UNIX is a multitasking, command-line operating system implemented on many different types of computers. Because it is both a stand-alone operating system and a network operating system, some call UNIX a multipurpose operating system. Linux is a popular, free, multitasking UNIX-type operating system. Solaris™, a version of UNIX developed by Sun Microsystems, is a network operating system designed for e-commerce applications.
The operating system on most handheld computers and small devices, called an embedded operating system, resides on a ROM chip. Popular embedded operating systems include Windows CE, Pocket PC OS, and Palm OS®. Windows CE is a scaled-down Windows operating system designed for use on wireless communications devices and smaller computers such as handheld computers, in-vehicle devices, and Web-enabled devices. Pocket PC OS is a scaled-down operating system developed by Microsoft that works on a specific type of handheld computer, called a Pocket PC. The Palm OS® is the operating system used on Palm handheld computers from Palm, Inc., and Visor handheld computers from Handspring™.Most operating systems include several utility programs that perform specific tasks related to managing a computer, its devices, or its programs. A file viewer is a utility that allows you to display and copy the contents of a file. A file compression utility shrinks the size of a file. A diagnostic utility compiles technical information about a computer’s hardware and certain system software programs and then prepares a report outlining any identified problems. An uninstaller is a utility that removes an application, as well as any associated entries in 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 disk defragmenter is a utility that reorganizes files and unused space on a computer’s hard disk so data can be accessed more quickly and programs can run faster. A backup utility copies, or backs up, selected files or an entire hard drive onto another disk or tape. A screen saver is a utility that causes the monitor’s screen to display a moving image on a blank screen if no keyboard activity occurs for a specified period.
System SoftwareSoftware is a key component of any information system. Of the total number of corporate dollars spent on computing, the software share is increasing while the hardware share is decreasing. Typically, different sizes of computers use different operating systems, and even the same types of computers may not use the same operating system. The operating system that a computer uses sometimes is called the software platform, or platform. Application software packages often require a specific software platform. A cross-platform application, however, is one that runs on multiple operating systems.
When you turn on a computer after it has been powered off, you are performing a cold boot. When you restart a computer that already has been powered on, you are performing a warm boot. Your typically can perform a warm boot by pressing a combination of keys on the keyboard (in Windows, CTRL+ALT+DEL), selecting options from a menu, or pressing a Reset button on the computer.
If you watch the screen closely as the POST is conducted, the value for the total amount of memory can be seen to change as it is measured in the memory test. If the POST results do not match the data on the CMOS chip, an appropriate message should appear. The boot program typically is the first side, first track, and first sector of the hard disk. When you install an operating system, one of the installation steps involves making an emergency disk from which you can start your computer if the hard disk is damaged.
You can interact with an operating system directly (as you do when copying files, moving files, formatting disks, and so on) or indirectly (as you do when working with an application program). An operating system is intended to be transparent; that is, it does not have to be understood, considered, or even known. The operating system with which an application program will work is specified on the application software package. The application programs you want to use should be considered before deciding on an operating system, and the operating system must be considered when choosing application software.
A graphical user interface is designed to be easier to use (more user-friendly) than a command-line interface. As an example of this user-friendly nature, consider how a relatively simple task, such as deleting a file, is performed with a command-line interface and with a GUI. With a command-line interface, you might type delfollowed by the file name in quotation marks. Therefore, you must remember the command, type it correctly, and use the proper syntax. On the other hand, with a GUI you need only select (click) the file name in the file manager window and then click the Delete command on a menu or the Delete button on a toolbar. Although most people find a GUI the easiest interface to use, some long-time computer virtuosos still feel a command-line user interface is more efficient.
Early operating systems were single user/single tasking, but today most operating system are multitasking. Multitasking can be cooperative, in which programs switch when they reach a logical break point, or preemptive, in which programs switch based on priority and an allocated amount of time. Early versions of Windows used cooperative multitasking; Windows 95 and subsequent versions use preemptive multitasking. Upon termination, most programs relinquish their space in memory, which then is reallocated by the operating system. Some programs, however, stay in memory after they terminate. As a class, these programs are called TSR (Terminate and Stay Resident) programs.
Virtual memory is employed with multitasking operating systems to maximize the number of programs that can use memory at one time. Paging, or the technique of swapping items between memory and storage, was developed before processors could address directly more than 1 MB of memory. All printers have buffers, and printer manufacturers are eager to sell DRAM. The term spooling comes from the observation that placing print jobs temporarily in a buffer is somewhat like winding thread onto a spool so that it can be used at a later time. Today, adding and configuring devices is easier because most devices support Plug and Play, which means the computer can recognize a new device and automatically load the necessary drivers. A feature of Windows 95, Plug and Play initially was greeted with mixed reviews. In fact, some wags claimed the new technology was more accurately called, “Plug and Pray.”Processor utilization – the amount of time that the processor is working and not idle – is one way of monitoring system performance. In addition to the programs that come with most operating systems, several utility programs are available to monitor system performance. Formatting a disk is the process of preparing it for reading and writing. Today, most floppy and hard disks are preformatted by the manufacturer. If you format a disk that already contains data, the formatting process erases the file location information, but it does not erase the actual files on the disk. Therefore, if you accidentally format a disk, often you can unformat it with a utility program. System security usually is most important for large systems or networks. For single-user PCs, adequate system security can be a key in the user’s pocket.
Many early operating systems were device dependent and proprietary. Device-dependent operating systems run only on a specific type of computer. Proprietary software is privately owned and limited to a specific vendor or computer mode. Today, the trend is towards device-independent operating systems that run on many manufacturers’ computers. Software that is not proprietary (i.e., that can work with a variety of computer models) sometimes is called portable or generic. Most of the operating systems discussed in this section are portable. When an operating system is proprietary, usually it is to boost hardware sales.
Operating systems for Apple computers and most mainframes initially were proprietary. Steve Wozniak, cofounder of Apple Computers, believes the decision to make its innovative Macintosh operating system proprietary was one of the company’s greatest mistakes. “We had the most beautiful operating system,” Wozniak writes, “but to get it you had to buy our hardware at twice the price.” Wozniak now feels the operating system should have been licensed.
Bill Gates, founder of Microsoft and one of the wealthiest men in the world, began his fortune with the MS-DOS operating system. Although developed for IBM, Microsoft retained the rights to the operating system and licensed the source code to several hardware manufacturers, which resulted in multiple variations. An application written for one type of DOS, however, will work with any other variation. A number follows each version of PC-DOS or MS-DOS. The integer portion of the number indicates a major release, while the decimal portion indicates updates. Thus, MS-DOS 6.2 means major version six, which has been updated twice. To a great extent, the popularity of DOS was a result of the large number of applications written to work with the operating system.
Windows 1.0, released in 1985, was Microsoft’s first attempt with a graphical user interface. It was not until five years later, however, with the release of Windows 3.0, that computer users began to take Windows seriously. Windows required 2 MB of memory (with 4 MB recommended) and an 80386 or newer processor, so it could not be used with many older PCs. Nevertheless, because Windows 3.0 was easier to use than DOS, eventually most software was written, and many popular DOS programs were rewritten, to work with Windows.Despite the advantages of Windows 95 and a heavily-funded promotional campaign, a poll of DOS and Windows 3.x users showed not everyone immediately embraced the new operating system. When asked how likely they were to adopt Windows 95 within the next six months, respondents replied:
Why are people often reluctant to adopt a new operating system?
- extremely likely 10%
- possible 35%
- not likely 53%
- don’t know 2%
The inclusion of Internet Explorer in the Windows 98 operating system led to an antitrust suit against Microsoft. Prosecutors insisted that the incorporation of a browser was an attempt by Microsoft to eliminate competition from rival Web browsers (such as Netscape Navigator). Microsoft maintained that the addition simply was an enhancement to the operating system. Although Microsoft advertised Windows 98 less heavily than Windows 95, many vendors took up the slack. One retailer offered Windows 98 with the opportunity to buy a new computer for $98. The promotion evidently worked. A buyer waited in line 11 hours for a chance to buy the new operating system and discount computer. When asked if he would have come out simply for Windows 98 (his current computer ran Windows 3.1), he replied, “Not a chance.”
Windows 2000 was released in February, 2000 and was touted as a boon for all businesses, from small companies with no more than two desktop computers to large corporations with vast networks. Windows Millennium is a result of Microsoft’s recognition that the needs of business and home users are different.
For years, the Macintosh operating system had features that made it far easier to use than other operating systems. For example, people could give files sensible names (like “Letter to Grandma”) instead of the cryptic, eight-character strings (like “letgrand.txt”) demanded by DOS and Windows 3.x. While Windows 95 incorporated many of these features, Macintosh devotees still feel their operating system is easier to use. Until recently, the Macintosh operating system was proprietary. In 1994 the operating system was licensed, but experts feel Apple’s promotion has been lukewarm. New standards let IBM computers run Apple software. More than 4,000 applications are designed to run under the Mac OS. Microsoft has developed the more popular Mac OS applications.
IBM supplies OS/2 (Operating System/2) Warp with its high-end personal computers. OS/2 originally was developed jointly by IBM and Microsoft to replace MS-DOS. As an interim measure, Microsoft developed Windows, an operating environment to work with DOS. The eventual popularity of Windows, coupled with the initial poor sales of OS/2, resulted in Microsoft and IBM going their separate ways, with Microsoft concentrating on Windows and IBM continuing to develop OS/2. Features offered in OS/2 Warp include:
- An enhanced graphical user interface
- Integrated business application software
- Speaker-independent speech recognition software
- Desktop objects that allow users to connect directly to the Internet
- Integrated Java programming language that allows Java applications to run without a Web browser
- Support for multiple CPUs using multiprocessing
Despite the current dominance of Windows, some believe Linux is the operating system of the future. Because Linux is freeware, users can modify and improve the program code. In addition, Linux is capable of running efficiently with less powerful processors, even the 80386. The story of Linux’s originator, Linus Torvalds, is told in the Technology Trailblazer on page 8.25.
The latest Palm handheld computer, Palm IIIC, offers a color screen. When paired with a portable, expandable, attachable, nearly full-sized keyboard and file compression software, some reviewers say the Palm IIIC almost can replace a laptop. The Visor handheld computer runs the same operating system as the Palm but offers several additional features – videogames, cell telephone, modem, MP3 player, and two-way pager – at about half the cost.
Utilities generally reside in storage until summoned by the user or operating system kernel. Microsoft was the target of several lawsuits for allegedly incorporating utility programs developed by others into their DOS operating system. Some versions of DOS were modified because of this litigation. In light of the ever-increasing number of utility programs included with operating systems, will a market remain for separate utility programs?
In addition to the utilities mentioned in this chapter, other Windows 98 utilities include:- DirectX – Enhances multimedia capabilities on the computer, providing better playback of different types of multimedia and managing 3-D graphics better than console computers.
- Drive Converter (FAT 32) – Converts the hard drive to the FAT32 file system, an enhancement that stores data more efficiently, creating extra disk space and helping programs run faster.
- Registry Checker – Finds and fixes registry problems each time the computer is started, automatically scanning the registry for inconsistent data structures.
- System File Checker – Keeps track of critical files that make the computer run, restoring the files if they are moved or changed.
- Microsoft Magnifier – Makes the screen more readable by displaying a magnified portion in a separate window and making it possible to alter the color scheme and contrast of the magnification window for easier visibility.
- Desktop enhancers – Change the desktop look and organization, allowing users to create and switch between multiple desktops.
- File conversion – Converts from one file format to another so that a file can be used by another application.
- Internet organizers – Helps in the management and use of favorite Web sites, searching the Web and reporting on site changes.
- Antivirus programs – Prevent, detect, and remove computer viruses. Viruses and antivirus programs are explored in Chapter 12.
Storage
Chapter 7: Storage
Memory, which is composed of one or more chips on the motherboard, is a temporary holding place for data and instructions during processing. The contents ofvolatile memory, such as RAM, are lost when the power to the computer is turned off. The contents of nonvolatile memory, such as ROM, are not lost when power is removed from the computer. Storage holds items such as data, instructions, and information for future use; that is, storage holds these items while they are not being processed. Storage is nonvolatile, which means the items in storage are retained even when power is removed from the computer. Compared to memory, the access time (the time it takes to locate a single item) for storage is slow.
A storage medium (media is the plural) is the physical material on which items are kept. A storage device is the computer hardware that records and retrieves items to and from a storage medium. Storage devices can function as sources of input and output. When storage devices transfer items from a storage medium into memory – a process called reading – they function as sources of input. When storage devices transfer items from memory to a storage medium – a process calledwriting – they function as sources of output. Types of storage media include floppy disks, hard disks, compact discs, tape, PC Cards, microfilm, and microfiche.
A floppy disk is a portable, inexpensive storage medium that consists of a thin, circular, flexible plastic disk with a magnetic coating enclosed in a square-shaped plastic shell. A floppy disk drive (FDD) is a device that can read from and write on a floppy disk. When you insert a floppy disk into a floppy disk drive, a shutteron the disk’s plastic shell slides to the side to expose the disk’s recording surface. A floppy disk is a type of magnetic media because it uses magnetic patterns to store items. Data is stored in tracks and sectors. A track is a narrow recording band that forms a full circle on the surface of the disk. The disk’s storage locations consist of pie-shaped sections, which break the track into small arcs called sectors. For reading and writing purposes, sectors are grouped into clusters. A clusterconsists of two to eight sectors and is the smallest unit of space used to store data. Formatting is the process of preparing a disk for reading and writing.
A high-capacity disk drive is a disk drive that uses disks with capacities of 100 MB and greater (remember, a typical floppy disk can store only up to 1.44 MB). High-capacity disks are used to store large graphics, audio, or video files and for backup. A backup is a duplicate of a file, program, or disk that can be used if the original is lost, damaged, or destroyed. Three high-capacity disk drives are the SuperDisk™ drive, the HiFD™ drive, and the Zip® drive. The SuperDisk™ drivereads from and writes on a 120 MB or 250 MB SuperDisk™. The HiFD™ (High-Capacity FD) drive reads from and writes on a 200 MB HiFD™ disk. TheZip® drive is a high-capacity disk drive that uses a Zip® disk. The Zip® disk is larger and thicker than a 3.5-inch floppy disk and can store 100 MB or 250 MB of data.
A hard disk, or hard disk drive, consists of several inflexible, circular platters that store items electronically. A platter in a hard disk is made of aluminum, glass, or ceramic and is coated with a material that allows items to be recorded magnetically on its surface. Each platter has two read/write heads, one for each side. Because of the stacked arrangement of the platters, the location of the read/write heads often is referred to by its cylinder, which is the location of a single track through all platters. Some computers improve hard disk access time by using a disk cache, which is a portion of memory that the processor uses to store frequently accessed items. A hard disk can be divided into separate areas, called partitions, each of which functions as if it were a separate hard disk drive.
An Internet hard drive is a service on the Web that provides storage to computer users. People use Internet hard drives to:
- Eliminate the need to transport files when away from a desktop computer
- Instantaneously save large audio, video, and graphics files when surfing the Web
- Make audio files, video clips, or pictures available to family, friends, co-workers, and customers
- Immediately view time-critical data and images while away from a main office or location
- Store offsite backups of data
A compact disc (CD) is a flat, round, portable metal storage medium that usually is 4.75 inches in diameter and less than one-twentieth of an inch thick. Compact discs store items using microscopic pits (indentations) and land (flat areas) that are in the middle layer of the disc. A high-powered laser light creates the pits in a single track, divided into evenly spaced sectors, that spirals from the center to the edge of the disc. A low-powered laser reads items by reflecting light off the disc surface. The reflected light is converted into a series of bits that the computer can process.
With proper care, a compact disc is guaranteed to last five years, but could last up to 50 years. Compact discs should not be stacked or exposed to excessive heat, cold, sunlight, or contaminants. A compact disc should be held by its edges (do not touch the underside of the disc) and placed in its protective case, called a jewel box, when it is not being used. You can clean the bottom surface with a soft cloth and warm water or a specialized CD cleaning kit, and you can repair scratches on the bottom surface with a specialized compact disc repair kit.
A CD-ROM, or compact disc read-only memory, is a compact disc that uses the same laser technology as audio CDs. For a computer to read items stored on a CD-ROM, you insert the disc into a CD-ROM drive or CD-ROM player. When viewing animation or video, the speed of a CD-ROM drive, or data transfer rate, is important. A higher the data transfer rate, results in smoother playback of images and sounds.
Most standard CDs are single-session because manufacturers record (write) all items to the disc at one time. Variations of standard CD-ROMs, such asPhotoCD, CD-R (compact disc-recordable), and CD-RW (compact disc-rewritable), are multisession, which means additional data, instructions, and information can be written at a later time. A PhotoCD is a compact disc that contains digital photographic images. A CD-R (compact disc-recordable) is a multisession compact disc onto which you can record your own items. A CD-RW (compact disc-rewritable) is an erasable disc you can write on multiple times.
A DVD-ROM (digital video disc-ROM) is an extremely high-capacity compact disc capable of storing from 4.7 GB to 17 GB. In order to read a DVD-ROM, you must have a DVD-ROM drive. You also can obtain recordable and rewritable versions of DVD. A DVD-R (DVD-recordable) allows you to write on it once and read (play) it many times. With the new rewritable DVD, called a DVD+RW, you can erase and record on the disc multiple times.
Tape, one of the first storage media used with mainframe computers, is a magnetically-coated ribbon of plastic capable of storing large amounts of data and information at low cost. Because it requires sequential access, or consecutive reading and writing of data, tape is used for long-term storage and backup. (Floppy disks, hard disks, and compact discs all use direct access, which means you can locate a data item immediately, without having to move through all the items stored in front of it.)
An enterprise storage system is a strategy that focuses on the availability, protection, organization, and backup of storage in a company. To implement an enterprise storage system, a company uses a combination of techniques. A server stores items needed by users on a network. A RAID system ensures that data is not lost. A tape library is a high-capacity tape system that works with multiple tape cartridges for storing backups of data, information, and instructions. A CD-ROM jukebox holds hundreds of CD-ROMs that can contain application programs and data. An Internet backup can store data, information, and instructions on the Web. A network attached storage (NAC) is an easy way to add hard disk space to a network. A storage area network (SAN) is a high-speed network that connects storage devices.
A PC Card is a thin, credit card-sized device that fits into a PC Card slot on a notebook or personal computer. PC Cards are used to add storage, memory, communications, and sound capabilities. A smart card stores data on a thin microprocessor embedded in a card similar in size to an ATM card. Two types of smart cards exist: intelligent and memory. An intelligent smart card contains a processor and has input, process, output, and storage capabilities. A memory card has only storage capabilities.
Microfilm and microfiche store microscopic images of documents on roll or sheet film. Microfilm uses a 100- to 215-foot roll of film. Microfiche uses a small sheet of film, usually about four inches by six inches. Libraries and large organizations use microfilm and microfiche to archive relatively inactive documents and files.
Output
Chapter 6: Output
Define The Four Categories Of OutputOutput is data that has been processed into a useful form called information. Four types of output are text, graphics, audio, and video. Text consists of characters (letters, numbers, punctuation marks, or any other symbol requiring one byte of computer storage space) that are used to create words, sentences, and paragraphs.Graphics are digital representations of nontext information such as drawings, charts, photographs, and animation (a series of still images in rapid sequence that gives the illusion of motion). Audio is music, speech, or any other sound. Video consists of images played back at speeds to provide the appearance of full motion. Anoutput device is any computer component capable of conveying information to a user.
A display device is an output device that visually conveys text, graphics, and video information. Information shown on a display device is called soft copy because the information exists electronically and is displayed for a temporary period of time. Display devices include CRT monitors, LCD monitors and displays, gas plasma monitors, and televisions. A CRT monitor is a monitor that is similar to a standard television set because it contains a cathode ray tube. A cathode ray tube (CRT) is a large, sealed, glass tube. The front of the tube is a screen coated with phosphor material that glows as an electron beam moves back and forth, which produces an image on the screen. LCD monitors and LCD displays use liquid crystal to present information on the screen. A liquid crystal display (LCD) has liquid crystals between two sheets of material. When an electric current passes through the crystals, they twist, causing some light waves to be blocked and allowing others to pass through, which creates the images.
Similar to an LCD display, a gas plasma monitor is a flat-panel display. A gas plasma monitor, however, substitutes a layer of gas for the liquid crystal material. When voltage is applied, the gas releases ultraviolet light that causes pixels on the screen to glow and form an image. An NTSC converter converts a computer’s digital signal into an analog signal that a standard television set can display. High-definition television (HDTV) is a type of television set that works with digital broadcasting signals and supports a wider screen and higher resolution than a standard television set.
The quality of a CRT monitor depends largely on its resolution, dot pitch, and refresh rate. The quality of an LCD monitor or display depends primarily on its resolution.A CRT monitor’s screen is coated with tiny dots of phosphor material, called pixels, that glow when electrically charged to produce an image. Resolution, which describes the sharpness and clearness of that image, is related directly to the number of pixels a monitor can display. The greater the number of pixels the display uses, the better the quality of the image. Dot pitch, a measure of image clarity, is the distance between each pixel on a display. The smaller the distance between pixels (dot pitch), the sharper the image. Refresh rate is the speed that a monitor redraws images on the screen. Refresh rate should be fast enough to maintain a constant, flicker-free image.
The resolution of an LCD monitor or display generally is proportional to the size of the monitor or display. That is, the resolution increases for larger monitors and devices.
The goal of ergonomics is to incorporate comfort, efficiency, and safety into the design of items in the workplace. Features that address monitor ergonomic issues include controls to adjust the brightness, contrast, positioning, and height and width of images. Newer monitors have digital controls that allow you to fine-tune the display. Many monitors also have a tilt and swivel base so the angle of the screen can be altered to minimize neck strain and glare. Monitors produce a small amount of electromagnetic radiation (EMR), which is a magnetic field that travels at the speed of light. High-quality monitors should comply with MPR II, a standard that defines acceptable levels of EMR for a monitor.A printer is an output device that produces text and graphics on a physical medium such as paper or transparency film. Printed information is called hard copybecause the information exists physically and is a more permanent from of output. Printers can be grouped in two categories: impact and nonimpact.
Impact printers form characters and graphics by striking a mechanism against an ink ribbon that physically contacts the paper. A dot-matrix printer is an impact printer that prints images when tiny wire pins on a print head mechanism strike an inked ribbon. A line printer is an impact printer that prints an entire line at one time. Two popular types of line printers are band printers and shuttle-matrix printers.
Nonimpact printers form characters and graphics without actually striking the paper. An ink-jet printer is a nonimpact printer that sprays drops of ink onto a piece of paper. A laser printer is a nonimpact printer that creates images using a laser beam and powdered ink, called toner. A thermal printer is a nonimpact printer that generates images by pushing electrically heated pins against heat-sensitive paper. Although the print quality of standard thermal printers generally is low, two special types of thermal printers, thermal wax-transfer printers and dye-sublimation printers, have a much higher print quality.
Some printers are used for special purposes. A photo printer is a color printer that can produce photo lab quality pictures as well as printing everyday documents. A label printer is a small printer that prints on an adhesive type material that can be placed on a variety of items. A portable printer is a small, lightweight printer that allows a mobile user to print from a notebook or handheld computer while traveling. Plotters are sophisticated printers used to produce high-quality drawings such as blueprints, maps, and circuit diagrams. A large-format printer, which operates like an ink-jet printer but on a larger scale, creates photo-realistic quality color prints.
An audio output device produces music, speech, or other sounds. Two commonly used audio output devices are speakers and headsets. Most personal computers have an internal speaker that outputs low-quality sound. Many users add high-quality stereo speakers or purchase PCs with larger speakers built into the sides of the monitor. A woofer can be added to boost low bass sounds. A headset plugged into a port on the sound card allows only the user to hear sound from the computer.
A data projector takes the image on a computer screen and projects it onto a large screen so that an audience of people can see the image. Two smaller, lower priced data projectors are an LCD projector, which uses liquid crystal display technology, and a digital light processing (DLP) projector, which uses tiny mirrors. A facsimile (fax) machine transmits and receives documents over telephone lines. A fax modem is a communication device that allows you to send (and sometimes receive) electronic documents as faxes. A multifunction device (MFD) is a single piece of equipment that looks like a copy machine but provides the functionality of a printer, scanner, copy machine, and sometimes a fax machine.
A terminal is a device that performs both input and output because it consists of a keyboard (input), a monitor (output), and a video card. A dumb terminal has no processing power and cannot function as an independent device. Dumb terminals connect to a host computer that performs the processing and then sends the output back to the dumb terminal. An intelligent terminal has memory and a processor that has the capability of performing some functions independent of the host computer. Some special-purpose terminals perform specific tasks and contain features designed for a particular industry. A point-of-sale (POS) terminal is a special-purpose terminal used to record purchases at the point where a consumer buys a product or service. An automatic teller machine (ATM) is a self-service, special-purpose terminal used to access your bank account.
For users with mobility, hearing, or vision disabilities, many different types of output devices are available. For example, hearing-impaired users can instruct programs to display words instead of sound. With the Windows operating system, physically challenged users can set options to make programs easier to use. Visually impaired users can change the size or color of text to make words easier to read. Blind users can use speech output, where the computer reads information that displays on the screen. A Braille printer outputs information in Braille onto paper.
Input
Chapter 5: Input
Describe The Two Types Of InputInput is any data or instructions entered into the memory of a computer. Two types of input are data and instructions. Data is a collection of unorganized items that can include words, numbers, pictures, sounds, and video. A computer processes data into information, which is organized, meaningful, and useful. Instructions can be in the form of programs, commands, or user responses. A program is a series of instructions that tells a computer how to perform the tasks necessary to process data into information. A command is an instruction given to a computer program. A user response is an instruction you issue to the computer by responding to a question posed by a computer program. Any hardware component that allows you to enter data, programs, commands, and user responses into a computer is an input device.
The keyboard is an input device that contains keys you press to enter data into a computer. Desktop computer keyboards usually have from 101 to 105 keys, while keyboards for smaller computers contain fewer keys. All keyboards have a typing area used to type letters of the alphabet, numbers, punctuation marks, and other basic characters. Many desktop computer keyboards also have a numeric keypad designed to make it easier to enter numbers, function keys programmed to issue commands and accomplish certain tasks, arrow keys used to move the insertion point (a symbol on the screen that indicates where the next typed character will display), and toggle keys that can be switched between two different states.
A standard computer keyboard sometimes is called a QWERTY keyboard because of the layout of its typing area. An enhanced keyboard has 12 function keys along the top row, 2 ctrl keys, 2 alt keys, and a set of arrow and additional keys between the typing area and the numeric keypad. Cordless keyboards transmit data via infrared light waves. Keyboards for notebook and handheld computers usually have smaller and fewer keys than desktop computers. A portable keyboard is a full-sized keyboard you can attach to and remove from a handheld computer. Some manufacturers have designed ergonomic keyboards to reduce the chance of workplace injuries. The goal of ergonomics is to incorporate comfort, efficiency, and safety into the design of workplace items.
In a graphical user interface, the pointer is a small symbol on the screen. A pointing device is an input device that allows you to control the pointer. Common pointing devices include the mouse, trackball, touchpad, pointing stick, joystick, touch screen, light pen, and a stylus. A mouse is a pointing device, designed to fit comfortably under the palm of your hand, that is moved across a flat surface. A trackball is a stationary pointing device with a ball mechanism on its top. A touchpad is a flat, rectangular pointing device that is sensitive to pressure and motion. A pointing-stick is a pressure-sensitive pointing device shaped like a pencil eraser that is positioned between keys on the keyboard. A joystick is a vertical lever mounted on a base. A light pen is a handheld device that contains a light source or can detect light. A touch screen is a touch-sensitive display on the screen. A stylus looks like a ballpoint pen but uses pressure, instead of ink, to write text and draw lines. An electronic pen can be used on a graphics tablet, which consists of a flat, rectangular, electronic plastic board used to input graphical data.
As you move a mouse across a flat surface, the movement is translated into signals that are sent to the computer, and the pointer on the screen also moves. When you move the mouse to the right, the pointer moves to the right on the screen. For Windows users, the top of a mouse has at least two buttons and sometimes also a wheel. Generally, you use a mouse to move the pointer on the screen to an object and then press a button, or click, to perform a certain action on that object. Other operations you can perform using a mouse include right-click, double-click, drag, right-drag, rotate wheel, and press wheel button.
A mechanical mouse has a rubber or metal ball on its underside. When the ball rolls in a certain direction, electronic circuits in the mouse translate the movement into signals that are sent to the computer. For better traction, you should place a mechanical mouse on a mouse pad. An optical mouse has no moving parts; instead it uses devices that emit and sense light to detect the mouse’s movement. An optical mouse can be used on nearly all surfaces, is more precise than a mechanical mouse, and does not require cleaning. A cordless mouse, or wireless mouse, is a battery powered device that transmits data using wireless technology, such as radio waves or infrared light waves. A cordless mouse uses technology very similar to that of a cordless keyboard.
Voice input is the process of entering data by speaking into a microphone that is attached to the sound card on a computer. Voice recognition is the computer’s capability of distinguishing spoken words. The first voice recognition programs were speaker dependent. With speaker-dependent software, the computer makes a profile of your voice, which means you have to train the computer to recognize your voice. Today, most voice recognition programs use speaker-independent software, which has a built-in set of word patterns and does not have to be trained to recognize your voice. Some voice recognition software requires discrete speech, meaning that you have to speak slowly and separate each word with a short pause. Most voice recognition products, however, support continuous speech, allowing you to speak in a flowing conversational tone.
To satisfy the input needs of many different types of users, handheld computers provide many different ways to input data. A handheld computer typically includes a basic stylus. With the stylus, you can enter data using an on-screen keyboard or using handwriting recognition software that translates handwritten letters and characters into symbols the computer understands. Other input alternatives available with some handheld computers include attaching a full-sized keyboard, transferring data from a desktop computer, using voice input, and attaching a digital camera.
A digital camera is used to take pictures and store the photographed images digitally instead of on traditional film. Pictures are stored on a storage medium, such as a floppy disk, SuperDisk, Clik! disk, PC Card, compact flash card, memory stick, mini-CD, or microdrive. Many digital cameras allow you to review and edit the images while they are in the camera. You also can download, or transfer a copy of, the stored image to a computer. Once on a computer, the pictures can be edited with photo-editing software, printed, faxed, sent via electronic mail, included in another document, or posted to a Web site. There are three basic types of digital cameras. A studio camera is a stationary digital camera used for professional studio work. A field camera is a portable camera, often used by photojournalists, that has many lenses and other attachments. A point-and-shoot camera is more affordable and lightweight and provides acceptable quality photographic images for the home or small business user.
Video input, or video capture, is the process of entering a full-motion recording into a computer and storing the video on a storage medium. Many video devices use analog video signals. To input video from these devices, the device is plugged into a video capture card, an expansion card that converts the analog signal into a digital signal the computer can understand. A digital video (DV) camera is a new generation of video camera that records video as digital signals, instead of using analog signals, and therefore does not require a video capture card. Video files can demand huge amounts of storage space. Video compression reduces the size of video files by recognizing that only a small portion of an image changes from frame to frame. Instead of storing every frame in its entirety, a video compression program might store an initial frame and then store only the changes from one frame to the next. A video decoder is a card that decompresses video. A video digitizer can be used to capture an individual frame from a video and save the still picture in a file.
A PC camera is a DV camera that allows home users to record, edit, capture video and still images, and make video telephone calls on the Internet. During a video telephone call, both parties can see each other as they talk. Although usually placed on top of the monitor and attached to a computer’s USB port, some PC cameras are portable and can be used anywhere. A Web cam is a video camera whose output displays on a Web page. Some Web sites have live Web cams that display still pictures and update the displayed images at specified time intervals.
Scanners and optical readers can capture data from a source document, which is the original form of the data. A scanner is a light-sensing input device that reads printed text and graphics and then translates the results into a form a computer can use. One of the more popular scanners is a flatbed scanner, which works similarly to a copy machine except it creates a file of the document in memory instead of a paper copy. Many scanners include OCR software, which converts a scanned image into a text file that can be edited. An optical reader uses a light source to read characters, marks, and codes and converts them into digital data that a computer can process. Three types of optical readers are optical character recognition, optical mark recognition, and bar code scanner. Optical character recognition (OCR) is a technology that reads typewritten, computer printed, or handwritten characters from ordinary documents and translates the images into a form that the computer can understand. Optical mark recognition (OMR) devices read hand-drawn marks such as circles or rectangles. A bar code scanner uses laser beams to read bar codes, which are identification codes consisting of vertical lines and spaces of different widths. Another type of reader, called a magnetic-ink character recognition (MICR) reader, reads text printed with magnetized ink and is used almost exclusively by the banking industry.
Identify Alternative Input Devices For Physically Challenged UsersWhether at work or at home, it may be necessary to obtain input devices that address physical limitations. Voice recognition is ideal for blind or visually impaired users, but several other input devices also are available. A keyguard, which is placed over the keyboard, allows people with limited hand mobility to rest their hands on the keyboard and guides a finger or pointing device so that only one key is pressed. Keyboards with larger keys and on-screen keyboards on which keys are pressed using a pointing device also can help. Pointing devices such as small trackballs controlled with a thumb or one finger and head-mounted pointers also are available for users with motor disabilities. Two new developments are gesture recognition and computerized implant devices. With gesture recognition the computer will be able to detect human motions. Computerized devices implanted in the brain will allow paralyzed individuals to transmit signals to the computer.
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