Touchpads and trackballs are both viable alternatives to a mouse, allowing users to manipulate an onscreen cursor intuitively and accurately. However, trackballs are a comparatively rare sight on both business and consumer laptop hardware, with the vast majority of manufacturers preferring to go with the touchpad. Looking at the reasons behind the touchpad's dominance of laptop control mechanisms gives a useful insight into the ways that users interact with electronic devices.

Comparison Although both devices are used for the same purpose, the touchpad and trackball differ widely in their use. A trackball can be thought of as an upturned mouse ball with surrounding buttons. You move the pointer on the screen by rotating the ball, and click as you would with a mouse. A touchpad, on the other hand, is a section of the laptop surface which is sensitive to finger movements. You move the onscreen pointer by touching the pad and swiping with your fingers.

Ergonomics One advantage touchpads have over trackballs is their construction. A touchpad consists of a few thin layers of capacitive material, while a trackball uses physical contacts to detect the movement of its ball. As such, touchpads can be made thinner than even small trackballs, and do not protrude from the laptop chassis itself. This makes them especially well suited to ultra-thin laptops such as the MacBook Air and Intel’s Ultrabook platform, which are usually designed to save space and reduce weight in every way possible.

Multi-Touch Many touchpads allow for some form of multi-touch or gesture-based input. A multi-touch touchpad is one that can recognize the contact of more than one finger at a time. This allows you to perform fairly complex actions -- such as zooming in or out and scrolling up and down a page -- using nothing but the touchpad, and without having to click on a separate onscreen element. However, the trackball has no equivalent feature, relying on traditional mouse-style commands to operate.

Buttons Although some touchpads do have physical buttons to click, many do not. Actions such as left-clicking and right-clicking are achieved by tapping a specific area of the pad. This increases flexibility, as it allows you to configure the “buttons” on their touchpad to your own personal preferences. For example, one user might prefer a simple left-click and right-click arrangement, while another might elect to have the bottom of the pad act as a “middle mouse button.” Trackballs, on the other hand, always require physical buttons to operate.

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