Magister Teknik Elektro
Pertemuan V
Input & Output
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.
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.
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• Keyboards
– 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 and terminals, includes
three types of terminals:
– (1) A dumb terminal has screen and keyboard and can input and
output but not process data. Why it's important: Dumb terminals are
used, for example, by airline reservations clerks to access a mainframe
computer containing flight information.
– (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.
» Why it's important: Such a terminal can perform some functions
independent of any mainframe to which it is linked. Examples
include the automated teller machine (ATM), a self-service
banking machine connected through a telephone network to a
central computer, and the point-of-sale (POS) terminal, used to
record purchases at a store's customer checkout counter.
Recently, many intelligent terminals have been replaced by
personal computers.
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Caption: Dumb terminals38
by airline reservations clerks
– (3) An internet terminal
» Terminal that provides access to the Internet. There are
several variants of Internet terminal: (1) the set top box or
web terminal, which displays web pages on a TV set; (2)
the network computer, a cheap, stripped-down computer
that connects people to networks; (3) the online game
player, which not only lets you play games but also
connects to the Internet; (4) the full-blown PC/TV (or
TV/PC), which merges the personal computer with the
television set; and (5) the wireless pocket PC or personal
digital assistant (PDA), a handheld computer with a tiny
keyboard that can do two-way wireless messaging.
» Why it's important: In the near future, most likely, Internet
terminals will be everywhere.
» Related Industry: WebTV is a well-known example of a
web terminal. There are two components to WebTV: the
set top box, and the subscription-based online service.
Microsoft Corporation purchased the latter, known as
WebTV Networks in 1997. It is now known as MSN TV.
Philips Magnavox manufactures the set top boxes.
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• Pointing Devices
– Devices that control the cursor or pointer on a screen
– 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, Movable ball, mounted on top of a stationary
device, that can be rotated using your fingers or palm. It looks
like the mouse turned upside down. Instead of moving the
mouse around on the desktop, you move the trackball with the
tips of your fingers. Why it's important: Trackballs require less
space to use than does a mouse.
– Pointing stick, which protrudes from the keyboard; and the
touchpad, a surface over which you move your finger. Why it's
important: Pointing sticks are used principally in videogames, in
computer-aided design systems, and in robots.
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• (2) The touch screen is a display screen that is
sensitive to touch.
– You find touch screens in kiosks, ATMs, airport tourist
directories, hotel TV screens (for guest checkout), and
cam-pus information kiosks making available everything
from lists of coming events to (with proper ID and
personal code) student financial-aid records and grades.
• (3) Devices for pen input include pen-based
computer systems, in which users write with a
pen-like stylus on a screen; light pens, lightsensitive penlike devices; and digitizers, which
convert drawings to digital data--one example is
the digitizing tablet.
– Pen computers use handwriting recognition software
that translates handwritten characters made by the
stylus into data that is usable by the computer.
– Why it's important: Many handheld computers and
PDAs have pen input, as do digital notebooks.
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– Digitizing Tablet
• One form of digitizer; an
electronic plastic board on
which each specific location
corresponds to a location on
the screen. When you use a
puck, the tablet converts
your movements into digital
signals that are input to the
• Why it's important: Digitizing
tablets are often used to
make maps and engineering
drawings, as well as to trace
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• 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.
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• (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 the
zebra-striped barcodes on products to translate them into digital code.
– Magnetic-ink character recognition (MICR) reads check numbers
(Scanning technology that reads magnetized-ink characters printed at
the bottom of checks and converts them to digital form. Why it's
important: MICR technology is used by banks to sort checks.);
– optical mark recognition (OMR) reads pencil marks (Scanning
technology that reads pencil marks and converts them into computerusable form. Why it's important: OMR technology is used to read the
College Board Scholastic Aptitude Test (SAT) and the Graduate Record
Examination (GRE). );
– optical character recognition (OCR) reads preprinted characters,
such as those on store price tags. Scanning technology that reads
special preprinted characters in a particular font (typeface design) and
converts them to digital code. Why it's important: OCR characters
appear on utility bills and price tags on department-store merchandise.
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Caption: Optical characters and an OCR device
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– 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; Specialized device that does nothing except
send and receive fax documents. Why it's important: Fax
machines permit the transmission of text and graphic data
over telephone lines quickly and inexpensively.
• fax modems are modems with fax capabilities.
– Input device installed as a circuit board inside the computer's
system cabinet; a modem with fax capability that enables you
to send signals directly from your computer to someone else's
fax machine or computer fax modem. Why it's important: With
this device, you don't have to print out the material from your
printer and then turn around and run it through the scanner on
a fax machine. The fax modem allows you to send information
more quickly than if you had to feed it page by page into a
machine. Fax modems are installed inside portable computers,
including pocket PCs and PDAs. If you can also link up a
cellular phone to a fax modem in your portable computer, you
can send and receive wireless fax messages no matter where
you are in the world.
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Fax modem
Dedicated Fax Machine
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• (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.
– Why it's important: Voice-recognition technology is useful in situations
where people are unable to use their hands to input data or need their
hands free for other purposes.
• (6) Sensors collect data directly from the environment and transmit
it to a computer.
– Why it's important: Although you are unlikely to see such input devices
connected to a PC in an office, they exist all around us, often in nearly
invisible form. Sensors can be used to detect all kinds of things: speed,
movement, weight, pressure, temperature, humidity, wind, current, fog,
gas, smoke, light, shapes, images, and so on. In aviation, for example,
sensors are used to detect ice buildup on airplane wings and to alert
pilots to sudden changes in wind direction.
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Caption: Earthquake sensor.
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Voice Recognition System
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• (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.
• Also known as RF-ID tagging; a source data-entry technology
based on an identifying tag bearing a microchip that contains
specific code numbers. These code numbers are read by the radio
waves of a scanner linked to a database.
• Why it's important: Drivers with RF-ID tags can breeze through
tollbooths without having to even roll down their windows; the toll is
automatically charged to their accounts. Radio-readable ID tags are
also used by the Postal Service to monitor the flow of mail, by
stores for inventory control and warehousing, and in the railroad
industry to keep track of rail cars.
• (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.
• Science of measuring individual body characteristics. Why it's
important: Biometric security devices identify a person through a
fingerprint, voice intonation, or other biological characteristic. For
example, retinal-identification devices use a ray of light to identify
the distinctive network of 38
slidesvessels at the back of the eyeball.
Caption: Humane Society employee scanning a pet cat implanted with an RF-ID microchip to identify its owner.
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Output Hardware converts machine-readable
information into people-readable form. Three
types of output are softcopy, hardcopy, and
Softcopy refers to non-printed data, such as that
shown on a display screen. Data on a display
screen or in audio or voice form. This kind of output
is not tangible; it cannot be touched.
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
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• Why it's important: Dot pitch is one of the measures of
display-screen crispness. For a .28dp monitor, for instance,
the dots are 28/100ths of a millimeter apart. Generally, a dot
pitch of .28dp will provide clear images.
• Pixel: Short for "picture element"; the smallest unit on the
screen that can be turned on and off or made different
shades. Why it's important: Pixels are the building blocks that
allow text and graphical images to be displayed on a screen.
• Resolution: Clarity or sharpness of display-screen images;
the more pixels there are per square inch, the finer the level
of detail attained. Resolution is expressed in terms of the
formula horizontal pixels x vertical pixels. Each pixel can be
assigned a color or a particular shade of gray. Standard
resolutions are 640 x 480, 800 x 600, 1024 x 768, 1280 x
1024, and 1600 x 1200 pixels. Why it's important: Users need
to know what screen resolution is appropriate for their
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• Refresh rate: number of times per second that
screen pixels are recharged so that their glow
remains bright. In general, displays are refreshed
45–100 times per second.
– Why it's important: The higher the refresh rate, the more
solid the image looks on the screen--that is, the less it
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Dot pitch
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• 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
– CRT: (Cathode ray tube)
Vacuum tube used as a
display screen in a
computer or video
display terminal. Why it's
important: This
technology is found not
only in the screens of
desktop computers but
also in television sets
and flight-information
monitors in airports.
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– Flat-panel screens
• 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.
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Caption: Softcopy vs. 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 non-impact 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. (PDL) Software that describes the shape and
position of characters and graphics to the printer. PostScript and PCL
are common page description languages. Why it's important: Page
description languages are essential to desktop publishing.
» Non-impact printer that creates images with dots. As in a
photocopying machine, images are produced on a drum, treated
with a magnetically charged ink-like toner (powder), and then
transferred from drum to paper.
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Laser 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.
» Printer that uses colored waxes and heat to produce
images by burning dots onto special paper. The
colored wax sheets are not required for black-andwhite output. Thermal printers are expensive, and
they require expensive paper. Why it's important: For
people who want the highest-quality color printing
available with a desktop printer, thermal printers are
the answer.
– 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.
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Caption: How an ink-jet printer works.
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• 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.
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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; higherfidelity audio using wave table synthesis and threedimensional 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."
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Input & Output Technology & Quality of
Life: Health & Ergonomics
The use of computers and communications
technology can have important effects on our
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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