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.22.A.The devicesinclude the keyboard, mouse, joystick, light pen, and trackball.Figure 1.22.ATypical inputdevices.LIGHT PENMONITORJOYSTICKSYSTEMUNITPOWER H.D.D TURBO RESET TURBOTRACKBALLMOUSEKEYBOARDThe most widely used pointing device is the mouse.Mice are hand-held devices that produce input data by being moved across asurface, such as a desktop.They may have 1, 2, or 3 buttons thatcan be pressed in different combinations to interact with softwarerunning in the system.The mouse enables the user to move acursor, or some other screen image, around the display screen.When a position has been selected, clicking one or more of themouse buttons enables the user to choose options from an on-screen menu, rather than type in commands from a keyboard.Specialized graphics software enable the user to operate themouse as a drawing instrument.In this context, the mouse can beused to create elaborate pictures on the screen.The TrackballMouse detects positional changes through a rolling trackball onwhich it rides.The most widely used output device for personal computers is theCathode Ray Tube (CRT) video display monitor, similar to the oneshown in Figure 1.22.B.Video display monitors often include a A+ Certification Training Guide64tilt/swivel base that enables the user to position it at whateverangle is most comfortable.This offers additional relief from eye-strain by preventing the user from viewing the display at an angle.Viewing the screen at an angle causes the eyes to focus separately,which places strain on the eye muscles.MONITORFigure 1.22.BTypical outputdevices.LCDPANELPOWER H.D.D TURBO RESET TURBOPRINTERSmall notebook and laptop computers use non-CRT displays, suchas Liquid Crystal Display (LCD) and gas-plasma panels.These displaysystems are well suited to the portability needs of these computers.They are much lighter and more compact than CRT monitors andrequire much less electrical energy to operate.Both types of dis-play units can be operated from batteries.After the monitor, the next most frequently added output deviceis the character printer, which produces hard copy output on paper.It converts text and graphical data from the computer into printon a page.SoftwareObjectives After the system s components are connected together and theirpower connectors have been plugged into a receptacle, the system Chapter 1 Microcomputer Fundamentals65is ready for operation.However, one thing is still missing: the soft-ware.Without good software to oversee its operation, the mostsophisticated computer hardware is worthless.Three general classes of software actually need to be discussed:.System software.Applications software.Games and learning softwareThe bulk of the software discussed in this book deals with thesystem software category.This is because this type of softwaretends to require more technical skills to manipulate and, there-fore, most often involves the service person.System SoftwareObjectivesThe System Software category consists of special programs used bythe system itself to control the computer s operation.Two classicexamples of this type of software are the system s Basic Input/Out-put System (BIOS) program and the Disk Operating System (DOS).These programs control the operation of the other classes of soft-ware.The BIOS is located in a ROM IC device on the systemboard.Therefore, it is commonly referred to as ROM BIOS.TheDOS software is normally located on a magnetic disk.Basic Input/Output SystemsWhen a PC is turned ON, the entire system is reset to a predeter-mined starting condition.From this state, it begins carrying outsoftware instructions from its BIOS program.This small programis permanently stored in the ROM memory ICs located on thesystem board.The information stored in these chips is all the in-herent intelligence that the system has to begin with.A system s BIOS program is one of the keys to its compatibility.Tobe IBM PC-compatible, for example, the computer s BIOS mustperform the same basic functions that the IBM PC s BIOS does [ Pobierz całość w formacie PDF ]

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