Г. В. Царева
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UNIT IVOUTPUT DEVICES  INTRODUCTORY TEXTWe interact with computers by entering instructions and data into them. After this information has been processed internally, we can see the results on the screen of the monitor. The characters and pictures that we see on the screen are made up of dots, also called picture elements (pixels). The total number of pixels in which the display is divided both horizontally and vertically is known as the resolution. If the number of pixels is very large we obtain a high resolution display and therefore a sharp image. Depending on your budget, there are a lot of options out there when it comes to computer monitors. With so many choices to consider, it is important to determine your needs before making your purchase. Important considerations are space available, size needed, and budget. CRT (Cathode Ray Tube) computer monitors were the most common computer monitors until flat panel screens became affordable. Similar to older TVs, CRT monitors still typically have much better contrast ratios and viewing angles than other computer monitor alternatives. LCD (Liquid Crystal Display) computer monitors save a lot of space and can even be mounted on walls. They provide a wide viewing angle and come in sizes typically ranging from 17-inches to 60-inches. Plasma computer monitors are less commonly used with computers due to their high operating temperatures, high power consumption, and fixed resolution. Touchscreen computer monitors provide a new way of interacting with your computer with a touch-sensitive screen. This allows users to interact directly with the application on screen without need for a mouse or keyboard. OLED (Organic Light Emitting Display) computer monitors are much thinner and brighter than LCD or Plasma screens. OLED monitors can also be placed on transparent surfaces, such as glass, allowing the user to see through them when not active. Printing is the final stage in creating the document. That is the purpose of the printers joined to the computing equipment. There are different types of printers and the results you can obtain with different types of printers vary substantially. It must be taken into account that printers vary in cost, speed, print quality and other factors such as noise or compatibility. First daisywheel and dot-matrix printers were of impact type that made them very noisy. Dot-matrix printers use a set of closely spaced pins and a ribbon to print letters or other characters on a page. Dot-matrix printers vary in terms of speed and the number of pins they have (between 50 and 500cps and the number of pins between 9 to 24). Dot matrix printers are commonly used for printing invoices, purchase orders, shipping forms, labels, and other multi-part forms. Dot matrix printers can print through multi-part forms in a single pass, allowing them to produce more pages than even high-speed laser printers. One common type of non-impact printer is an ink-jet printer. It operates by firing a fine spray of quick-drying ink onto paper. The ink jet is formed into the required character by electrostatic fields. Almost all inkjets offer a color option as standard, in varying degrees of resolution. Inkjet printers are capable of producing high quality print which almost matches the quality of a laser printer and quite fast printing at the rate of up to about 400 cps. Laser printers are extremely fast, printing a complete page at a time. They scan the image with a laser beam and transfer it to paper with a special ink powder. They are constantly being improved. In terms of speed and quality they are preferred by experts for different reasons: they have a wider range of scalable fonts, they can emulate different language systems, they can produce graphics, and they have many other advantages. Plotters are a special kind of printer. Plotters use ink and fine pens held in a carriage to draw very detailed designs on paper. They are used for construction plans, engineering drawings and other technical illustrations. Finally, multifunction printers: combine top-quality color ink-jet or laser printing with plain-paper and PC faxing, color copying and color scanning , telephoning- all in one convenient, space-saving machine. If you work from home or have a small office a multifunctional device may be ideal. |