1.1.3.2 Types of Pointing Devices

Perhaps the most commonly available pointing device is a ``mouse'' A mouse is a hardware device that can be moved on a surface. The pointer of a GUI mirrors the motion of a mouse. This way, a user can intuitively control the location of the pointer of a GUI.

This device is called a mouse because the original devices were corded, and the cord looked like the tail of a mouse. However, many computer mice are cordless, and so the name ``mouse'' is no longer appropriate. Note that a mouse typically has two to three buttons on it. We'll discuss how buttons are used later.

Although mice are intuitive for most users, they are not portable. For this reason, various pointing devices are invented for notebook computers, or situations where there is no space for a mouse. Most current notebook computers have touchpads. A touchpad is a device with a small flat surface (about 8cm by 6cm). It is touch sensitive. Consequently, a user can slide a finger tip across a touchpad, and the motion is mirrored by the pointer of a GUI. Most touchpads also come with two buttons.

IBM (now Lenovo) notebook computers have a touchpoint device, often in addition to a touch pad. A touchpoint is a hardware device that looks like the erase of a pencil. It is pressure sensitive. As a user applies pressure to a touchpoint in different directions, the pointer of an interface moves accordingly. The speed of movement depends on the amount of pressure applied. The touchpoint is a very compact device that does not use up much space on a keyboard, often between the `G', `H' and `B' keys. It is also considered more efficient because a user does not need to move his/her hand from the keyboard to the pointing device. Nonetheless, using a touchpoint effectively requires more practice than what most users are willing to invest.

Last, but not least, is the trackball. The trackball design actually predates the design of a mouse. A trackball device is a freely rotating ball that is located on a stationary device. The motion of the ball of a trackball device is mirrored by matching motion of the point of a GUI. A trackball has several advantages over a mouse. For example, it can be used with a large GUI display easily, without having to move-pick-up-move. A trackball also tends to be more accurate than a mouse for critical applications like computer aided design (CAD).