Information Technology Reference
In-Depth Information
Summary
Selecting and Using Input Devices
Input devices
allow the user to communicate with the computer. The most common input
devices are a
keyboard
and
mouse
, both of which can be either wired or wireless. A keyboard can
have an
ergonomic
design to prevent hand and wrist strain. Devices that lack a real keyboard use a
virtual keyboard
(software-based) to enable user input.
A pointing device controls the onscreen pointer in the user interface. A mouse can be
mechanical
or
optical
. Other pointing devices include
trackball
and
touchpad
. Some computers have a
touch
screen
on which your finger can serve as a pointing device. A
drawing tablet
enables you to input
drawings using a
stylus
.
A scanner
digitizes
a hard-copy photo using a
charge-coupled device (CCD)
. A scanner can
be part of a
multi-function device (MFD)
that also includes a printer and copier. A
bar code
reader
is a specialized type of scanner used for reading
Universal Product Code (UPC)
symbols.
Magnetic bar code readers
and
radio frequency identification (RFID) chips
are other types of
scanning devices, as are
optical mark recognition (OMR)
systems and
magnetic-ink character
recognition (MICR)
systems.
A capture device captures new content, rather than scanning existing content. Examples include
digital cameras
and
digital video cameras
. A
webcam
is a digital video camera that must remain
connected to a computer in order to function.
Audio input can be used to control a computer with commands and to input music and sounds.
Audio input requires an
audio adapter
(sound card). When using a microphone for audio input,
voice recognition software
interprets speech by matching words in a database;
speech recogni-
tion software
is teachable software that learns an individual's pronunciation.
Selecting and Using Output Devices
A
display screen
is a video screen the computer uses for outputting information to the user. A
stand-alone display screen is called a
monitor
.
Liquid crystal display (LCD)
is a popular type
of flat-screen monitor technology. A newer alternative is
organic light-emitting diode (OLED)
.
An LCD screen can be either
active matrix
(a version of which is
thin-film transistor
) or
passive
matrix
. In active matrix, each
pixel
has its own transistor. A
high-definition TV (HDTV)
can
also be used as a computer monitor via a
high-definition multimedia interface (HDMI)
.
Cathode ray tube (CRT)
is an older monitor technology that uses a vacuum tube and electron
guns to light up colored phosphors on a glass screen. Phosphors are arranged in triads of red,
green, and blue.
Some specialized display types include
e-paper
(for book readers),
digital whiteboards
, and
digi-
tal projectors
. Projector brightness is measured in lumens.
A display screen has a
maximum resolution
, expressed as a number of pixels horizontally and
vertically. The ratio of horizontal to vertical is its
aspect ratio
. The
refresh rate
is the number of
times per second the display is refreshed. The number of bits needed to describe the color of a
pixel is the
color depth
. A
display adapter
tells the display screen what to do.
The key factors in selecting a printer include initial cost, cost per page for
consumables
, print
resolution (expressed in
dots per inch
), speed, color, interface, and paper handling.
