Buttons and a rotary encoder for the scrollwheel
round out the unit. Although optical mice outperform mechanical mice in most environments,
they require a slightly textured or speckled surface to work well (hence,
the sudden popularity of speckled and woodgrain patterns on office furniture instead
of the solid colors popular a few years ago). I??™ve found that they may be sensitive to
bright light at a low angle (such as sunlight at sunrise or sunset), which may cause
them to skip or temporarily stop functioning.
1.10
1.10 Display Hardware 13
The memory and raw processing capability of many modern optical
mice exceeds that of the first computer used to run Unix!
Keyboards
Like mice, keyboards are sometimes used in parallel. This is most common on laptops,
where an add-on numeric keypad may be used along with the built-in keyboard,
or a larger external keyboard is used in preference to the internal one.
Keyboards typically have PS/2 or USB connectors; USB versions always operate at
low speed (1.5 Mbps). The keyboard sends a scancode corresponding to a button
location when that button is pressed, and sends another code when that button is
released. This permits the system to detect how long buttons are held down and in
what combination.
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