 |  Using Information Technology: A Practical Introduction to Computers and Communications, 5/e Brian K. Williams Stacey Sawyer
HARDWARE INPUT & OUTPUT: Taking Charge of Computing and Communications
Web SummaryInput & Output. Input Hardware consists of devices that translate
data into a form the computer can process.The people-readable form
of the data may be words, but the computer-readable form consists of binary
0s and 1s, or off and on electrical signals. Output Hardware consists of devices that translate information processed by the computer
into a form that humans can understand. The computer-processed information
consists of 0s and 1s, which need to be translated into words, numbers,
sounds, and pictures. - Input Hardware. Input Hardware -- devices that translate data into a form the computer
can process--may be divided into three categories: keyboards, pointing
devices, and source-data entry devices.
Keyboards: There are two categories of keyboards,
devices that convert characters into electrical signals readable by the
processor. The first is the traditional computer keyboard, which
has all the keys of a typewriter plus some that are unique. The second category,
specialty keyboards andterminals, includes three types
of terminals: (1) A dumb terminal has screen and keyboard and can input and output but not process data.
(2) An intelligent terminal
has screen, keyboard, and its own processor and memory. One example is the
automated teller machine (ATM), the self-service banking machine.
Another is the point-of-sale (POS) terminal, used to record purchases
in a store. (3) An internet terminal
provides access to the Internet. Examples are set-top boxes or Web
terminals, stripped-down network computers, online game players,
PC/TVs, and handheld wireless pocket PCs or personal digital
assistants (PDAs). Pointing Devices: Devices that control the cursor or pointer on
a screen are pointing devices. They include the mouse and its variants,
the touch screen, and various forms of pen input. (1) The mouse,
which directs a pointer on the display screen, is moved on the desktop.
Variants are the trackball, a movable ball mounted on a stationary
device; the pointing stick, which protrudes from the keyboard; and
the touchpad, a surface over which you move your finger. (2) The
touch screen is a display screen that is sensitive to touch. (3)
Devices for pen input include pen-based computer systems, in which
users write with a penlike stylus on a screen; light pens,
light-sensitive penlike devices; and digitizers,
which convert drawings to digital data--one example is the digitizing tablet.
Source Data-Entry Devices: Source-data entry devices create machine-readable
data on magnetic media or paper or feed it directly into the computer's processor.
As well as various scanning devices--imaging systems, bar-code readers, mark-
and character-recognition devices, and fax machines--they include audio-input
devices, video input, photographic input (digital cameras), voice-recognition
systems, sensors, radio-frequency identification devices, and human-biology
input devices. (1) Scanners use laser beams and reflected light to
translate images of text, drawings, and photographs into digital form. One
type is an imaging system,
which converts text, drawings, and photos into digital form that can be processed
or stored in a computer system. This has led to the new industry of electronic imaging,
the integration of separate images using scanners. Another scanning device
is the bar code reader,
which reads thezebra-striped barcodes
on products to translate them into digital code. Magnetic-ink character recognition (MICR)
reads check numbers; optical mark recognition (OMR)
reads pencil marks; optical character recognition (OCR)
reads preprinted characters, such as those on store price tags. The fax machine,
the last type of scanner, reads images and sends them over phone lines. Dedicated fax machines
only send and receive fax documents; fax modems
are modems with fax capabilities. (2) Audio-input devices translate analog
sounds (those with continuously variable waves) into digital 0s and 1s, either
through audio boards or MIDI boards. (3) Video-input cards translate analog
film and videotape signals into digital form, using either frame-grabber video
cards or full-motion video cards. (4) Digital cameras
use light-sensitive processor chips to capture photographic images in digital
form. (5) Voice-recognition systems convert speech into digital signals
by comparing electrical patterns produced by voices with prerecorded patterns
stored in a computer. (6) Sensors collect data directly from the environment
and transmit it to a computer. (7) Radio-frequency identification (or
RF-ID tagging)is based on an identifying tag bearing microchip that
contains code numbers; these numbers are read by radio waves of a scanner
linked to a database. (8) Human-biology input devices include biometric
systems, which use biometrics
the study of body characteristics, to identify people through biological characteristics,
and line-of-site systems, in which people point their eyes at a screen.
- Output Hardware. Output hardware converts machine-readable information into people-readable
form. Three types of output are softcopy, hardcopy, and other.
Softcopy: Softcopy refers to nonprinted data, such as that shown
on a display screen. A display screen (monitor, screen) shows programming
instructions and data as they are being input and information after it is
processed. Screen clarity is affected by dot pitch,
or space between pixels (the small units on screen that can be turned
on or off); by resolution, which involves the number of pixels per
square inch; and by refresh rate, the number of times per second
pixels are recharged. Two types of monitors are CRT and flat-panel. A CRT
(cathode-ray tube) is a vacuum tube. A flat-panel display
consists of two plates of glass separated by a layer of a substance in which
light is manipulated; one technology is liquid crystal display (LCD),
in which molecules of liquid crystal create images by transmitting or blocking
light. Flat-panel screens are either active-matrix display,
in which each pixel on screen is controlled by its own transistor and so
the image is brighter and sharper, or passive-matrix display,
in which a transistor controls a row or column of pixels. Two common color
and resolution standards for monitors are SVGA (the most common),
which can produce 16 million possible colors, and XGA, which can
produce 65,536 possible colors.
Hardcopy: Hardcopy
refers to printed output. A printer prints characters or images on
paper or another medium. Resolution of the image is measured by dpi (dots per inch), with more dots producing greater sharpness. Two types
of printers are impact printers and nonimpact printers. Impact printers
form images by striking a print hammer or wheel against an inked ribbon, leaving
an image on paper; one type is the dot-matrix printers,
which contains a print head of small pins. Nonimpact Printers
form characters or images without direct physical contact between printing
mechanism and paper. Three types of nonimpact printers are laser, ink-jet,
and thermal. A laser printers
creates images with dots like a photocopying machine; the printer uses a page description language,
software that describes the images to the printer. An ink-jet printers sprays electrically charged droplets of ink at high speed onto paper.
A thermal printer uses colored waxes and heat to burn dots onto special
paper. A special kind of printer, the plotter, which may be ink-jet
or electrostatic, produces high-quality graphics, such as maps, that are too
large for regular printers. Another category of printer is the multifunction printer,
which combines printing, scanning, copying, and faxing in one device.
Other Output: Other forms of output are sound, voice, and video. Sound-output
devices produce digitized sound. Voice-output devices convert digital
data into speech-like sounds. Video consists of photographic images,
played at 15-29 frames per second; in one form of video output called videoconferencing
people have online meetings using computers and communications devices that
enable them to see and hear one another.
- The Future of Input & Output. Increasingly, input will be performed
in remote locations and will rely on source data automation. Future source
data automation will include high-capacity bar codes, 3-D scanners, more sophisticated
touch devices, smarter smart cards, more diverse sensors, better voice recognition,
smaller electronic cameras, more sophisticated biometric devices, and even
brainwave input devices.
Output, too, is being performed in remote locations. On the horizon are
better, cheaper, and larger display screens; higher-fidelity audio using
wavetable synthesis and three-dimensional sound; and "real-time"
video using digital wavelet theory. Thanks to 3-D technology, three-dimensional
images can appear on computer displays and, through VRML software, users
of the World Wide Web can experience 3-D "virtual worlds." - Input & Output Technology & Quality of Life: Health & Ergonomics.
The use of computers and communications technology can have important effects
on our health. Some of these are repetitive stress (strain) injuries (RSIs)
such as carpal tunnel syndrome; computer vision syndrome,
such as eyestrain and headaches; and back and neck pains. Some people are
concerned about electromagnetic fields (EMFs),
waves of electrical and magnetic energy emitted from CRTs, cellphones, and
the like.
Negative health effects have increased interest in the field of ergonomics,
the study of the relationship of people to a work environment.
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