They are also used for applications that require

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Unformatted text preview: r solid. The arrangement of pins in an 18-pin print head of a dot-matrix printer is shown in Figure 9.27. Since dot matrix printers produce printed output as patterns of dots, they can print any shape of character that a programmer can describe. This allows the printer to print many special characters, different sizes of print, and the ability to print graphics such as charts and graphs. Dot-matrix printers are impact printers because they print by hammering the pins on the inked ribbon to leave ink impressions on the paper. Hence they can be used to produce multiple copies by using carbon paper or its equivalent. However due to impact printing, dot-matrix printers are noisy as compared to non-impact printers. Since dot-matrix printers use inked ribbon to produce printed output, they are usually monochrome. However, some dot-matrix printers use a ribbon having rows of two to three colors to produce printed output in selected few colors. Figure 9.27. The arrangement of pins in an 18-pin print head of a dot-matrix printer. It permits dots to overlap to increase the244 I Foundations of Computing Dot-matrix printers are normally slow with speeds usually ranging between 30 to 600 characters per second. However they are cheap in terms of both initial cost and cost of operation. Hence they are preferred by individuals and organizations for generating printed outputs if the speed and quality of printing are not important factors. They are also used for applications that require multicopy output such as shipping forms and invoices, which rely on impact for generating multiple copies. InkJet Printers InkJet printers are character printers that form characters and all kinds of images by spraying small drops of ink on to the paper. The print head of an inkjet printer contains up to 64 tiny nozzles, which can be selectively heated up in a few micro seconds by an integrated circuit register. When the register heats up, the ink near it vapourizes and is ejected through the nozzle and makes a dot o...
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