Ch# 6 What Is Out Put?

CH# 6 WHAT IS OUT PUT? Out put is data that has been processed into a useful form. That is, computer process input (data) into output (information).

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Types of Out put • While working with a computer, a user encounters four basic categories of output: text, graphics, audio, and video.

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• Text-Example of text-based documents are memorandums, letters, announcements, press release, reports, advertisements, newsletters, envelopes, and mailing labels. • Graphics-Documents often include graphics to enhance their visual appeal and convey information. 06-SPA-11 (P.2)

• Audio-Users insert their favorite music CD in a CD or DVD drive and listen to the music while working on the computer.

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• Video-As with audio, software and Web sites often include video clips to enhance understanding. Users watch a live or prerecorded news repots, view a movie, see a doctor perform a life-saving surgery, observe a hurricane in action, or enjoy a live performance of their favorite jazz band on the computer.

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DISPLAY DEVICES • A display device, or simply display, is an output device that visually conveys text, graphics, and video information. Information on a display device, sometimes called soft copy, exists electronically and appears for a temporary period.

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Types of Display Devices • Two types of display devices are CRT monitors and flat-panel display.

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CRT MONITORS • A CRT monitor is a desktop monitor that is similar to a standard television because it contains a cathode-ray tube. A cathode-ray tube (CRT) is a large, sealed glass tube. The front of the tube is the screen. Tiny dots of phosphor material coat the screen on a CRT. Each dot consists of a red, a green, and a blue phosphor. The three dots combine to make up each pixel.

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A pixel is a single point in an electronic image. Inside the CRT, an electron beam moves back and forth across the back of the screen. This causes the dots on the front of the screen to glow, which produces an image on the screen. CRT monitors for desktop computers are available in various sizes, with the more common being 15,17,19,21, and 22 inches. 06-SPA-11 (P.2)

Quality of a CRT Monitor • The quality of a CRT monitor depends largely on its resolution, dot pitch and refresh rate. Resolution describes the sharpness and clearness of an image. Manufactures state the resolution of a monitor in pixels. For example, a monitor set at an 800-*600 resolution display, up to 800 pixels per horizontal inch and 600 pixels per vertical inch, for total of 480,000 pixels to create a screen image.

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HOW VIDEO TRAVELS FROM THE PROCESSOR TO A CRT MONITOR • Step 1: The processor sends digital video data to the video card. • Step 2: The video card’s digital-to-analog converter (DAC) converts the digital video data to an analog signal. • Step 3: The analog signal is sent through a cable to the CRT monitor. 06-SPA-11 (P.2)

• Step 4: The CRT monitor separates the analog signal into red, green, and blue signals. • Step 5: Electron guns fire the three color signals to the front of the CRT. • Step 6: An image is displayed on the screen. When the electrons hit phosphor dots on the back of the screen. 06-SPA-11 (P.2)

FLAT PANEL DISPLAYS • A flat-panel display is a display device with a shallow depth that does not use CRT technology. LCD monitors, LCD screens, gas plasma monitors, and many HDTV’s are types of flat-panel displays.

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LCD Monitors and Screen • An LCD monitor, also called an LCD flat panel monitor, is a desktop monitor that uses a liquid crystal display instead of a cathode-ray tube to produce images (Figure 6-9). These monitors produce sharp, flicker-free images.

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LCD Technology • A liquid crystal display (LCD) uses a liquid compound to present information on a display computer LCD’s typically have fluorescent tubes that emit light waves toward the liquid crystal cells, which are sandwiched between two sheets of material (Figure 6-12). When an electrical charge passes through the cells, the cells twist. This twisting causes some light waves to be blocked and allows others to pass through, creating images on the display. 06-SPA-11 (P.2)

Gas Plasma Monitors • A gas plasma monitor is a display device that uses gas plasma technology, which substitutes a layer of gas for the liquid crystal material in an LCD monitor. When voltage is applied, the gas release ultraviolet (UV) screen to glow and form an image.

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PRINTERS • A printer is an output device that produces text. And graphics on a physical medium such as paper or transparency film. Printed information, called hard copy, exists physical and is a more permanent form of output than that presented on a display device (soft copy).

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Impact Printers • An impact printer forms characters and graphics on a piece of paper by striking a mechanism against an inked ribbon that physically contacts the paper. Impact printers characteristically are noisy because of this striking activity. • Two commonly used types of impact printers are dot-matrix printers and line printers.

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Dot-Matrix Printers • A dot-matrix printers is an impact printer that produces printed images when tiny wire pins on a print head mechanism strike an inked ribbon. When the ribbon presses against the paper, it creates dots that form characters and graphics.

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LINE Printers • A line printer is a high-speed impact printer that prints an entire line at a time (Figure 6-18). The speed of a line printer is measured by the number of lines per minute (1pm) it can print. Some line printers print as many as 3,000 1pm.

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Non impact Printers • A non impact printer forms characters and graphics on a piece of paper without actually striking the paper. Some spray ink, while others use heat or pressure to create images.

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