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Pointing Devices NUMERIC PADS POINTING DEVICES Powered By Docstoc
                      A separate set of
Numeric   keypad          on some keys
                        that keyboards
                   contain the numbers
                     0 through 9 and a
                          point decimal
                     arranged as on an
                       adding machine.
                      Numeric keypads
                      make it easier to
                   enter large amounts
                        data of numeric

Non-Programmable   Programmable
           Pointing Devices
A pointing device is an input interface that
allows a user to input data to a computer
using physical gestures - point, click, and
drag - for example, by moving a hand-held
mouse across the surface of the physical
desktop and activating switches on the
mouse. Movements of the pointing device are
echoed on the screen by movements of the
.pointer (or cursor) and other visual changes
While the most common pointing device by
far is the mouse, many more devices have
been developed.
  This is the most common form of pointing
device for computers. Typically it has up to
three keys and may have a scrolling wheel.
The mouse's motion typically translates into
 the motion of a pointer on a display, which
 ..allows for fine control of a user interface.
 The user should have the ability to modify
  the speed of movement of the cursor, the
    distance moved by the cursor and the
              .double-click interval
Motion and targeting
Most computer operating systems allow the user to adjust the speed that
the pointer moves on the screen when the mouse is moved. People with
restricted movement can use very small motions to move the pointer a
long distance on the screen. Alternatively for those who struggle with
targeting accuracy the pointer movement can be slowed so that targets
are easier to hit .

                  Targets are items or areas on the screen that can be
clicked, such as buttons and links on web pages. Targets can also be
made easier to click if they are made larger. This can be accomplished by
reducing the screen resolution or fine-tuning the display options.
There are also some third-party accessibility utilities available to help
people who have difficulty with motion and targeting, particularly for
those with a hand tremor.
Alternative pointing devices
Roller / Track Ball

                       Roller or trackballs consist of a small ball rotating
freely in a fixed bed containing sensors to detect rotation of the ball about
two axes. These devices are sometimes incorporated in public access
terminals since, unlike a mouse, they do not need a surface to work on and
they are more resistant to vandals .

People with a mobility impairments use trackballs as an alternative input
device. The control surface of a trackball is easier to manipulate and the
buttons can be activated without affecting the pointer position. Some
physically impaired users find trackballs easier since they only have to move
their thumb relative to their hand, instead of moving the whole hand, while
others incur unacceptable fatigue of the thumb .Elderly people sometimes
have difficulty holding a mouse still while double-clicking; the trackball allows
them to let go of the cursor while using the button. However trackballs can
be problematic for users with poor manual dexterity, and they have a
tendancy to be slightly slower than a mouse.
DJ Supplementary switch

 Many people find that the most difficult part of using a mouse is
  holding it steady while pressing the button. One solution is to
   consider adding an external switch to act as the left or right
                     .mouse button, or both

                           Specialist joysticks, classed as an

assistive technology pointing device, are used to replace the
computer mouse for people with fairly severe physical disabilities
by pluging into the USB port and controlling the mouse pointer .
They can be of either displacement or force type. Displacement
joysticks are by far the most common type and are what most
people envisage when they consider joysticks. Force applied to the
handle causes it to move over several degrees (usually between 20
and 30).
This movement is detected and converted to an electrical signal by
a potentiometer or a non-contacting technology device.
Displacement joysticks are better for positioning accuracy than
positioning speed, but it is essential that they return to the default
position (usually the centre) when released .

 This is a computer display screen that is sensitive to touchscreen A
    human touch, allowing a user to interact with the computer by
 touching an active area, target or control such as pictures or words
on the screen. Touchscreens are activated by the insertion or removal
  active areas or targets ,controls of the fingertip or by pressing the
   . .)with a mouthstick, headstick, or other similar device (stylus)

 A touchpad (also trackpad) is a pointing device consisting of
specialized surface that can translate the motion and position
of a user's fingers to a relative position on screen. They are a
   common feature of laptop computers and also used as a
substitute for a computer mouse where desk space is scarce.
  Touchpads vary in size but are rarely made larger than 10
                      .square centimetres
  The most common technology used to operate touchpads
entails sensing the capacitance of a finger, or the capacitance
   between sensors. Because of the property being sensed,
capacitance-based touchpads will not sense a stylus or other
  similar implement. Gloved fingers or prosthetic limbs will
                 .generally also be problematic
Light Pen

 A light pen is a computer input device in the form
of a light-sensitive wand used in conjunction with a
 computer's monitor. It allows the user to point to
   displayed objects, or draw on the screen, in a
   similar way to a touchscreen but with greater
 positional accuracy. A light pen can work with any
    CRT-based display, but not with LCD screens,
         .projectors and other display devices
 The light pen became moderately popular during
the early 1980s. Due to the fact that the user was
   required to hold his or her arm in front of the
  screen for long periods of time, the light pen fell
    .out of use as a general purpose input device
Eye tracking

Eye tracking devices can be a powerful alternative for
individuals with no control, or only limited control, over
.their hand movements
A camera mounted on a computer monitor is focused
on one eye. The available software processes the
camera image to determine where the user is looking
(gaze point), and the cursor is then placed at the gaze
point. "Mouse clicks" are done with either a slow eye
blink, eye gaze or a supplementary switch. Special
software allows the person to type, and may include
word-completion technology to speed up the process.
.These systems can be very costly