Although the mouse is a handy tool, some people do not like using a mouse or have difficulty maneuvering
one. For others, a mouse requires too much desktop space—a real problem when you are not working at a
For these reasons and
others, hardware makers
have developed devices that
duplicate the mouse's functionality but interact with
the user in different ways. The primary goals of these "mouse variants
" are to
provide case of use while taking up less space than a mouse. They all remain stationary and can even be built into the keyboard.
A trackball is a pointing device that works like an upside-down mouse
. You rest
your index finger or thumb on an exposed ball, then place your other fingers on
the buttons. To move the pointer around the screen, you roll the ball with your index finger or thumb. Because you do not move the whole device, a trackball requires less space than a mouse. Trackballs gained popularity with the advent of laptop computers, which typically are used on laps or on small work surfaces that
have no room for a mouse.
Fig. 1: Computer mouse trackball.
Trackballs come in different models, as shown in Fig. 1
. Some trackballs are large and heavy with a ball about the same size as a cue ball. Others are much smaller. Most trackballs feature two buttons, although three-button models are also available. Trackball units also are available in right- and left-handed
The trackpad (also called a touchpad) is a stationary pointing device that many
people find less tiring to use than a mouse or trackball. The movement of a finger
across a small touch-sensitive surface is translated into pointer movement on the
computer screen. The touch-sensitive surface may be only 1.5 or 2 inches square,
so the finger never has to move far. The trackpad's size also makes it suitable for
a notebook computer. Some notebook models feature a built-in trackpad rather
than a mouse or trackball (see Fig. 2
Fig. 2: Modern notebook computers and desktop
keyboards features a built-in trackpad.
Like mice, trackpads usually are separate from the keyboard in desktop computers and are attached to the computer through a cord. Some special keyboards
feature built-in trackpads. This feature keeps the pad handy and frees a port that
would otherwise be used by the trackpad.
Trackpads include two or three buttons that perform the same functions as
mouse buttons. Some trackpads are also “strike sensitive," meaning you can tap
the pad with your fingertip instead of using its buttons.
Pointers in the Keyboard
Many portable computers now feature a small joystick positioned near
the middle of the keyboard, typically
is controlled with either forefinger, and it controls the movement
of the pointer on screen. Because
users do not have to take their hands
off the keyboard to use this device,
they can save a great deal of time
and effort. Two buttons that perform the same function as mouse
buttons are just beneath the spacebar and are pressed with the thumb.
Fig. 3: joystick in keyboard.
Several generic terms have emerged for this device; many manufacturers refer to it as an integrated pointing device, while others call it a 3-D point stick. On the IBM ThinkPad line of notebook computers, the pointing device is called the TrackPoint (see Fig. 3).