llightpen
l enabled users to point to a
spot on a screen and to perform a select, position, or other task
l it allows direct control by
pointing to a spot on the display
l incorporates a button for the
user to press when the cursor is resting on the desired spot on the screen
l lightpen has three
disadvantages: users' hands obscured part of the screen,
l users had to remove their
hands from the keyboard, and
l users had to pick up the
lightpen
ltouchscreen
l allows direct control touches
on the screen using a finger
l early designs were rightly
criticized for causing fatigue, hand-obscuring-the-screen,
l
hand-off-keyboard, imprecise pointing, and the
l eventual smudging of the
display
l lift-off strategy enables
users to point at a single pixel
l the users touch the surface
l then see a cursor that they
can drag around on the display
l when the users are satisfied
with the position, they lift their fingers off the display to activate
l can produce varied displays
to suit the task
l are fabricated integrally
with display surfaces