Pointing Devices

Today's portable computers come with built-in pointing devices. Most of these pointing devices are one of three types: trackball, trackpoint, or trackpad.

• Trackball. This small ball (approximately .5 inch in diameter) is partially embedded in the keyboard below the spacebar. The user's fingers manipulate the ball. These devices are accurate and serviceable, but they are unpopular because of their tendency to gather dirt and dust, which dramatically reduces performance.

• Trackpoint. IBM developed the trackpoint, which many manufacturers install in their systems. It is a small, rubberized button (approximately .25 inch in diameter) located above B and below G and H on the keyboard. The user nudges it in any direction (rather like a tiny version of a joystick) to move the cursor around the screen. It is convenient because the user's hands don't need to leave the keyboard to manipulate the trackpoint.

• Trackpad. The trackpad (also known as the touchpad) is the most recent development of the three. It is an electromagnetically sensitive pad measuring about 1 inch × 2 inches located in the keyboard below the spacebar. It responds to the movement of a finger across its surface to move the cursor. Tapping the pad simulates mouse clicks (although buttons are also provided). It is a truly innovative device, but does tend to be overly sensitive to accidental touches and taps. It is also sensitive to humidity, so moist fingers can cause unpredictable performance.