A small Powerpoint about Input and Output Devices

1. Input and Output
Devices
Ethan Sawyer

2. The mouse is the most known about input device, the mouse is
able to work on almost any surface, the mouse has a small, red
light-emitting diode (LED) that bounces light off that surface onto
a complementary metal-oxide semiconductor (CMOS) sensor.
The CMOS sensor sends each image to a digital signal processor
(DSP) for analysis. The DSP, operating at 18 MIPS (million
instructions per second), is able to detect patterns in the images
and see how those patterns have moved since the previous image.
Based on the change in patterns over a sequence of images, the
DSP determines how far the mouse has moved and sends the
corresponding coordinates to the computer. The computer moves
the cursor on the screen based on the coordinates received from
the mouse. This happens hundreds of times each second, making
the cursor appear to move very smoothly.
Input - Mouse

3. The keyboard is the second most known about input device,
the keyboard is able to work on any surface. A computer's
keyboard is a small computer in its own right, complete
with a processor and other circuitry to interpret your
keystrokes. Most of this circuitry runs the computer's key
matrix, which is the grid of circuits beneath the keys. In
most keyboards, these circuits are incomplete under each
key. When you press a key, it completes the circuit and
allows an electrical current to pass through. The processor
detects that completed circuit and compares its location on
the key matrix with the character map, or lookup table,
which tells the processor what that keystroke represents.
Input - Keyboard

4. A touchpad allows users to drag their fingers along in the
direction they want the mouse pointer to go. It does this by
sensing the pressure of the finger along a vertical and
horizontal electrode grid just beneath the surface "skin." AC
travels through the electrodes to the circuits. These circuits
check the capacitance of both grid layers against each other.
This determines where the pointer is and where it should be
moved to. It's sort of an electronic version of triangulation
in that the touchpad has to take your three-dimensional
movements, figure out where your finger is and where it's
going, and then translate this into two-dimensional
movement of the pointer on the screen.
Input - Touch Pad

5. Output - Screen - LCD
LCD technology works by blocking light. An LCD is made of two pieces of
polarized glass that contain a liquid crystal material between them. A
backlight creates light that passes through the first piece of glass. At the
same time, electrical currents cause the liquid crystal molecules to align
to allow varying levels of light to pass through the second piece of glass
and create the images you see. These monitors have several advantages
over the traditional cathode ray tube (CRT) technology. LCDs have a
slimmer design and consume less energy. Plus, they have a much better
resolution (the number of individual dots of color, called pixels
contained in a display.) They also give less eyestrain because they don't
display a flicker like CRT monitors do. And they are more adjustable, you
can adjust the height, tilt or swivel or mount them on a wall.

6. Output - Projector - LCD
LCD stands for Liquid Crystal Display. The way this places an image on a screen is
fascinating and not nearly as complex as you might imagine. A bulb is set up to shine
a fairly powerful light through a prism. The prism splits the light into its component
colors and these are sent through small LCD screens. The screens themselves are
sent signals to allow just so much of the light through at specific pixel locations. The
light is then beamed through a lens onto a screen where the images can be seen by
the human eye. One of the first advantages of digital LCD projectors deals with
colour saturation. LCD designs generate better colour saturation than DLP designs.
This is because DLP projectors aim too boost brightness at the expense of colour
saturation. Therefore, digital LCD projectors will provide an image that is more rich.
One of the first disadvantages of digital LCD projectors is pixilation. These projectors
produce images using individual pixels which can become visible on large screens.
This will give the appearance of looking through a screened door when using digital
LCD projectors on large screens. This is normally a problem when watching video
instead of looking at data.

7. Output - Speakers
When speakers are at work, an electric signal reproduced by an amplifier passes through
the speaker wire which varies in terms of its frequency and its power. The signal enters the
speaker through the binding posts and the wiring inside the cabinet and is sent to the
voice coil. The force on the voice coil undulates back and forth, as the signal's amplitude
and frequency changes. The voice coil rapidly vibrates along the axis of the magnet
structure causing the cone to vibrate. The air molecules immediately around the cone are
pressurized and they translate into the sounds we hear.
Speakers are usually provided with the computer, they're very simple to operate, they
help blind people who would otherwise have difficulty using a computer, they can be
useful for alerting computer users, even when they're busy, such as in pop-ups. But, they
can take up a fair amount of desk-space, compared to headphones and they can distract
people around you therefore disrupting a communal work area.