Input Devices
Input devices are devices that allow the user to input data into a computer. The most obvious input devices are pointing devices (mice and their equivalents) and keyboards. Other input devices include such things as microphones used in the case of voice recognition systems. This chapter is limited to discussion of keyboards and common pointing devices.
Pointing Devices
The most common pointing device is the mouse. Others include the trackball, touchpad, and track stick ("pencil eraser") controls found on some laptops. All but the last one come in different forms.
Pointing Device Types
Pointing devices can be divided into interface type, features, and detection system.
Mouse Interfaces
Mice can be connected to PCs in at least one of four ways: serial (DB-9 female connector), PS/2 (the small, round, 5-pin connector), USB, and infrared or radio frequency wireless. Many mice come with adapters so that an individual mouse can be used in both PS/2 and serial ports, or both PS/2 and USB ports. More information about these follows:
Serial: This is the original interface used in personal computers. Serial devices are hot-pluggable. Although new computers no longer come with serial mice, the vast majority of computers have serial ports, so a serial mouse is the perfect choice when the built-in PS/2 port fails. In fact, serial mice used to come with drivers on floppy disks, although Windows 95 and later have the drivers.
PS/2: This is the standard mouse interface for the vast majority of computers with ATX and similar motherboards. These computers have dedicated PS/2 mouse ports that can be used only for PS/2 pointing devices and those adapted to PS/2. These devices are not hot-pluggable; plug in and remove only with the computer's power off. There is no guarantee that ignoring this warning will fry the motherboard, but it is not worth the risk. Windows installs PS/2 mice transparently to the user unless the device has unusual features, in which case, a software disk might be needed.
Note Many laptops have one PS/2 port. A keyboard or a pointing device can be plugged into this port. Y-connectors are available that allow both a pointing device and a keyboard to be plugged in simultaneously. However, not all Y-connectors work with all brands of laptops; there are at least two types of Y-connectors for this purpose. Make sure to match up one that will work with the brand you're using.
USB: This is the standard mouse port for many new computers. However, because most computers still have PS/2 mouse ports, unless the mouse you want is available only in USB, it is a good idea to use a PS/2 mouse. This is because there are many devices that use USB ports, but only one that can use a PS/2 mouse port, so you might as well save the USB port for some other device. Most of the feature-laden mice use USB. USB devices are recognized and installed by Windows, and many come with software disks. Windows, however, has drivers for almost all commercially available mice. USB mice are also good choices for replacements when PS/2 ports fail.
Wireless: Wireless mice use one of the other interfaces in this list. They come in two varieties, infrared and radio frequency (RF). The RF types are usually preferred because the receiver and mouse do not have to be directly in line of site of each other. The mouse runs on battery power, so plan to have spare batteries on hand or at least hold on to a basic wired mouse in case of an emergency.
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