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The typical mouse connects to a PC via either a PS/2 or USB cable, though some are use the wireless, often using Infra-red, or Bluetooth to connect to the PC; some still further use a traditional wireless frequency of 2.4 GHz or 5 GHz. Most PC mice have 2 buttons, however, many hardware manufacturers sell specialty mice with several. A notable exception to this is the Apple Macintosh mouse, which has only one button, using a keyboard key in combination with a click to simulate multiple buttons.
The mouse functions by moving over a smooth, flat surface (usually a mousepad, although this is less of a concern for optical mice for most surfaces) and reporting the movement back to the PC. Mice generally use one of two modes to detect movement; the first is a ball located in the bottom of the mouse. The ball moves across the surface, rolling two small mechanisms inside the mouse, which tell the computer the speed and direction in which the mouse is travelling.
The second, more common method, is called optical, and typically uses a red light and an image recognition unit to record movement. Recently, Logitech created a third type of movement tracking with lasers. Similar to optical input, this type of mouse uses the laser for image recognition to detect movement over the surface.
A similar input device is the trackball, which may appear similar to a mouse flipped on its back, with its ball pointed upwards, with a mouse button either side.