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Lesson 11. Peripherals > Understanding Device Classes - Pg. 242

Peripherals 242 Understanding Device Classes Mac OS X groups devices into device classes, or types, to determine how to interact and support the devices' functionality. Most applications are not concerned with what buses' devices are connected. All they need to know are the types of devices connected. The operating system handles interaction across the various buses. For example, when using the Finder, you are able to retrieve files from a storage device whether the device is connected via FireWire, USB, or ATA. The three most common types of devices are human input devices, digital cameras and scanners, and storage devices. Human Input Devices One of the most common device types connected to a Macintosh computer is a human input device, part of the human interface device (HID) class. The HID class includes all of the devices that allow you to input data or control the computer. Some of the devices in this class include mice, keyboards, joysticks, and graphics tablets. Digital Cameras and Scanners To support digital cameras and scanners, Mac OS X includes the Image Capture framework. When you plug in a supported digital camera, or press a scanner's Scan button, Mac OS X detects the action and opens an appropriate application to handle the camera or scanner. By default, iPhoto (/ Applications) opens for cameras, and Image Capture (/Applications) opens for scanners. You can specify alternate applications in the Preferences menu in the Image Capture utility. Mac OS X supports digital cameras in three ways: it directly supports those that implement Photo Transfer Protocol (PTP); it uses the mass storage driver to access those that emulate a storage device and mount automatically on the desktop; and the Image Capture utility connects to cameras that have an Image Capture plug-in (/Library/Image Capture/Devices).