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In this chapter, you learn what is output and what are output devices. Display devices are introduced, including CRT monitors, flat-panel displays, video cards, and high-definition television. You explore monitor quality and monitor ergonomics. Various types of printers are presented, such as impact printers, nonimpact printers, portable printers, plotters and large-format printers, and special-purpose printers. You find out about audio output and other output devices, including data projectors, facsimile machines, and multifunction devices. Finally, you become acquainted with terminals and output devices for physically challenged users.
Define the four categories of output
Output 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. An output device is any computer component capable of conveying information to a user.
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Identify the different types of display devices
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.
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Describe factors that affect the quality of a display device
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.
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Identify monitor ergonomic issues
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.
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Explain the differences among various types of printers
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 copy because 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.
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Describe the uses of speakers and headsets
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.
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Identify the purpose of data projectors, fax machines, and multifunction devices
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.
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Explain how a terminal is both an input and output device
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.
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Identify output options for physically challenged users
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.
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|Expand Your Knowledge|
Here you will find additional information that will expand and enhance your knowledge beyond that contained in your textbook. Compare this information to what may be provided in a traditional classroom by your instructor or peers.
For computer users, output may be the most significant stage of the information processing cycle. Output is the goal of input and processing. It provides the information users need to work and make decisions. Output used by a machine often is an intermediate result. Eventually it will be processed into a form that can be used by people.
Sound Blaster is the de facto standard for computer audio. You may be familiar with audio output from certain cars and vending machines: “Fasten seat belts” or “Please deposit twenty-five cents.” Voice output telephone calls promoting banks, services, or political candidates are increasingly common. Yet, audio output is not always welcome. Voice output once was employed in grocery store checkouts. Because of negative public reaction, however, it has been discontinued.
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Although “soft” implies a touchable quality, soft copy only has an electronic, intangible existence, unlike the physical presence of hard copy (printed material).
So much information today is in color that sales of monochrome monitors have plummeted. A number of less expensive monitors that use gray scaling, however, are popular among business users.
The CRT in a monitor uses from 15,000 to 20,000 volts to accelerate electrons from the gun to the screen. Servicing of monitors, therefore, only should be done by trained personnel. Color monitors sometimes are known as RGB monitors (for red, green, and blue). Red, green, and blue are light’s primary colors. These three fundamental colors are not the same as the three primary pigments you may have mixed in art class (red, yellow, and blue). Believe it or not, when red light and green light mix the result is seen as yellow light.
Application software sometimes requires a specific video standard for optimal performance. A factor to keep in mind when purchasing a monitor is that any video card capable of a higher resolution can run programs that require lower resolution levels – a concept called backward compatibility. The CGA standard monitor, introduced in 1981, had a 640 x 200 resolution and displayed four colors. Today’s SVGA monitor has a resolution more than 6 times better and can display 16.7 million colors. Although flat-panel displays use relatively little power and the clarity of the images they produce continues to improve, they are not as bright as CRT monitors. Because active matrix displays are much clearer than passive matrix displays, most of today’s notebook computers have active matrix displays. LCD screens often are backlighted but consume microwatts of power and give off virtually no heat. Gas plasma screens, while much brighter, consume hundreds or thousands of times more power than LCDs.
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In some ways, pixel images on a monitor are similar to the works created by pointillist painters like Georges Seurat.
The flickering that is seen on some monitors is a result of a too-slow refresh rate. Older monitors refresh images using a technique called interlacing, in which the an electron beam draws only half the horizontal lines with each pass. Most of today’s monitors are noninterlaced. For the eyes, noninterlaced monitors tend to be less tiring than interlaced monitors. All video display devices look better in a dark environment.
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Studies show that working in an ergonomically designed environment lessens fatigue, reduces injury, and increases productivity.
Varying requirements have led to the development of printers with different capabilities. In addition to the questions posed in Figure 6-15, the following factors should be considered when purchasing any printer:
- What is the total printer cost? (Supplies and maintenance should be weighed along with initial price.)
- How much is the printer used? (The duty cycle, or recommended maximum output per month, and the mean time between failure (MTBF), or estimated time before a component needs service, are key considerations.)
- What type of output will be produced? (A printer’s capabilities must match output requirements.)
- Who will use the output? (External correspondence requires better quality printing than internal-only reports.)
- Are multiple copies necessary? (Only impact printers can produce multiple copies on a single pass.)
- Is color required? (Color significantly adds to the cost of some printers.)
- Where will the printer be used? (Impact printers are noisy in closed locations, but are more resistant to extreme conditions.)
For a printer to function, the appropriate printer driver must be installed in the computer. Drivers are software that transform the computer’s output into signals a printer can understand and use. Most printer manufacturers include driver software. Because most printers are 1,000 times slower than computers, all printers have a buffer that temporarily stores a few pages, allowing the computer to dump output into the buffer and continue processing.
Print quality depends on dots per inch and the amount of overlap. Letter quality (LQ) print corresponds to that produced by a typewriter. Many impact printers produce near letter quality (NLQ) print, which is slightly less clear than letter quality. Although most dot-matrix printers use continuous-form paper (in which individual sheets are connected together), some also can use single-sheet paper without removing any paper by “parking” continuous-form paper while a single sheet is printed.
Nonimpact printers represent the fastest growing segment of the printer market. One attraction of nonimpact printers is their quiet operation. Imagine the noise level in an office with several impact printers operating simultaneously! Due to separate development, printer resolution is expressed in dots per inch while monitor resolution is stated in pixels per inch (which is dependent on dot pitch). The resolution of a high-end printer is about 10 times better than the resolution of an SVGA monitor. Although high resolution is good, more dpi requires additional memory.
Unlike other types of nonimpact printers, the image produced by ink-jet printers can smear if moistened. Although laser printers are popular, they do not handle all printing jobs well. Special feeders are needed to print multiple envelopes, and multipart forms cannot be used at all.
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Like other computer components, high-quality speakers are growing smaller. NXT has developed speakers for its flat-panel technology that deliver superior sound despite being only one sixty-fourth of an inch thick. The speaker technology has been licensed by NEC, Acer, and Mission and is included in their new PCs and notebooks.
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Other Output Devices
Data projectors are particularly useful when demonstrating computer software packages. A data projector, along with the modem-equipped notebook computer and portable printer, is part of the arsenal of business travelers. With these weapons, the “road warrior” can create, transmit, receive, and project sales presentations.
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Terminals also sometimes are called display terminals or video display terminals (VDTs). Historically, terminals have been dumb and dependent on a mainframe, to which they were connected by a cable, called an umbilical cord, for any processing. The advent of inexpensive personal computers gave rise to terminals with independent processing capabilities. Personal computers that function as intelligent terminals are connected to switch boxes that allow them to operate as PCs or to access a mainframe. Although they are intelligent terminals, some workstations are designed without disk drives so restricted data cannot be downloaded or copied. Some terminals, such as credit card authorization devices in department stores, look very little like normal computers. POS (point-of-sale) terminal printers are special-purpose printers used at supermarket checkouts. These usually are low-grade dot-matrix printers that have seven or nine pins.
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Output Devices for Physically Challenged Users
If, when using Windows, the Accessibility command does not appear on the Accessories submenu, you may have to install Accessibility Options. To install Accessibility Options, open the Add/Remove Programs Properties dialog box at the Windows Setup tab by clicking Start, pointing to Settings, clicking Control Panel, double-clicking Add/Remove Programs, and then clicking the Windows Setup tab. If you used a CD to install Windows, you will be prompted to insert it into your computer. Under Components, click to select the Accessibility Options check box and then click OK.
In Windows, the Accessibility Properties dialog box can be used to change both input and output options for physically challenged users. To open the Accessibility Properties dialog box, click the Start button, point to Settings, click Control Panel on the Settings submenu, and then double-click the Accessibility Options icon in the Control Panel dialog box. The Accessibility Properties dialog box can be used to change:
Keyboard options – StickyKeys (allows the shift, >alt, and ctrl keys, which usually are used with other keys, to be used by pressing one key at a time), FilterKeys (ignores brief or repeated keystrokes), and ToggleKeys (plays a tone when a toggle key is pressed)
Sound options – SoundSentry (generates visual warnings when a sound is made) and ShowSounds (displays captions for program speech and sound)
Display options – High Contrast (uses colors and fonts designed for easy reading)
Mouse options – MouseKeys (allows pointer to be controlled with the numeric keypad)
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