Encyclopedia of Computer Science and Technology

printers 381Microsoft PowerPoint is the most widely used presentationprogram. It includes the ability to import Excelspreadsheets, Word documents, or other items created byMicrosoft Office suite applications. The user can switchbetween outline view (which shows the overall structure ofthe presentation) to viewing individual slides or workingwith the slides as a collection.There are a number of alternatives available includingApple’s Keynote and Open Office, which includes a presentationprogram comparable to PowerPoint. Another alternativeis to use HTML Web-authoring programs to createthe presentation in the form of a set of linked Web pages.(PowerPoint and other presentation packages can also converttheir presentations to HTML.) Although creating presentationsin HTML may be more difficult than using aproprietary package and the results may be somewhat lesspolished, the universality of HTML and the ability to runpresentations from a Web site are strong advantages of thatapproach.A number of observers have criticized the general samenessof most business presentations. Some presentationdevelopers opt to use full-fledged animation, created withproducts such as Macromedia Director.Further ReadingImpress: More Power to Your Presentations. Available online. URL:http://www.openoffice.org/product/impress.html. AccessedAugust 17, 2007.Keynote (Apple iWork). Available online. URL: http://www.apple.com/iwork/keynote/. Accessed August 17, 2007.Lowe, Doug. PowerPoint 2007 for Dummies. Hoboken, N.J.: Wiley,2007.Rutledge, Patrice-Anne, Geetesh Bajaj, and Tom Muccolo. SpecialEdition Using Microsoft Office PowerPoint 2007. Indianapolis:Que, 2006.A dot-matrix printer uses an array of pins controlled by solenoids.Each character has a pattern of pins that are pushed against a typewriter-likeribbon to form the character on the paper.printersFrom the earliest days of computing, computer users neededsome way to make a permanent record of the machine’s output.Although results of a program could be punched ontocards or saved to magnetic tape or some other medium, atsome point data has to be readable by human beings. Thisfact was recognized by the earliest computer and calculatordesigners: Charles Babbage (see Babbage, Charles)designed a printing mechanism for his never-finished computing“engine,” and Williams Burroughs patented a printingcalculator in 1888.Typewriter-Like PrintersThe large computers that first became available in the 1950s(see mainframe) used “line printers.” These devices haveone hammer for each column of the output. A rapidly movingband of type moves under the hammers. Each hammerstrikes the band when the correct character passes by.Printing is therefore done line by line, hence the name. Lineprinters were fast (600 lines per minute or more) but like themainframes they served, they were bulky and expensive.The typewriter offered another point of departure fordesigning printers. A few early computers such as theBINAC (an offshoot of ENIAC) used typewriters riggedwith magnetically controlled switches (solenoids). However,a more natural fit was with the Teletype, inventedearly in the 20th century to print telegraph messages. Sincethe Teletype is already designed to print from electricallytransmitted character codes, it was easy to rig up a circuitto translate the contents of computer data into appropriatecodes for printing. (Since the Teletype could send as well asreceive messages, it was often used as a control terminal forcomputer operators or for time-sharing computer users intothe 1970s.)The daisy-wheel printer was another typewriter-likedevice. It used a movable wheel with the letters embeddedin slim “petals” (hence the name). It was slow (about10 characters a second), noisy, and expensive, but it wasthe only affordable alternative for early personal computerusers who required “letter-quality” output.Dot-Matrix PrintersThe dot-matrix printer, which came into common usein the 1980s, uses a different principle of operation thantypewriter-style printers. Unlike the latter, the dot-matrixprinter does not form solid characters. Instead, it uses an