Transcript 5 Input and Output

5
Input and
Output
5
Objectives:
• To understand that input and output
devices are essentially translators.
• To understand that input devices
translate symbols that people
understand, into symbols that
computers can process.
5
• To understand that output devices
translate machine output to output
people can comprehend.
Input
• Input is any data or instructions that are
used by a computer.
• It can come directly from the user or
from other sources.
5
• You can enter data and issue
commands using your keyboard, voice,
by pointing to items, and by writing on
special devices.
Input
• Input devices are hardware devices that
convert people-readable data into machinereadable form.
• Common input devices are the keyboard to
enter text and a mouse to issue commands.
• Other input devices are scanning, image
capturing, digitizing, and audio-input devices.
5
Input
• Input devices must translate human
language to machine language.
• The computer can only understand
machine language, which is
represented by a binary system of
electronic signals (0s and 1s).
5
KEYBOARD ENTRY
• The keyboard is a common way to input
data.
• The keyboard combines a typewriter
keyboard with a numeric keypad and
special keys.
• The keyboard converts numbers,
letters, and special characters into
electrical signals.
5
• Traditional, ergonomic, and folding are
types of keyboards.
Keyboards
• Numeric Keypad - Enters numbers,
arithmetic symbols, controls cursor or
insertion point.
• Function Keys - Shortcut for specific
tasks such as F1 for online Help.
5
• Escape Key - Typically cancels a
selection or a procedure.
• Windows Key - Displays the Start menu.
Keyboards
• Spacebar - Enters blank spaces between
characters.
• Navigation Keys - Control the cursor or
insertion point on the screen.
• Toggle Keys - Keys that turn a feature on or
off – Caps Lock, Num Lock, Scroll Lock.
• Combination Keys - Keys that perform an
action when held down in combination with
5
another key – Ctrl, Alt, Shift.
Keyboards
• Special Keys - Keys above arrow keys
to the right of keyboard.
5
POINTING DEVICES
• Pointing devices provide a comfortable
interface with the system unit, by
accepting point gestures and converting
them into machine-readable input.
• Use of pointing devices reduces human
errors that may occur during keyboard
entry.
5
• Direct entry includes pointing, scanning,
and voice-input devices.
Pointing Devices
• The pointing devices used in direct entry
include the following:
• Mouse – a device that controls the cursor or
pointer displayed on the monitor.
• Touch Screen – a special kind of monitor
screen covered with a plastic layer.
• Light Pen – a light-sensitive pen like device.
5
Types of Mouse Devices:
•
Mechanical Mouse
–
–
•
Optical Mouse
–
–
–
–
5
Has a ball on the bottom and is attached to the system
unit with cable.
Controls the pointer when rolled on a tabletop.
Does not require a flat surface.
Has no moving parts.
Emits and senses light to detect movement.
Can be used on any surface, is more precise.
Types of Mouse Devices:
•
Cordless Mouse
–
–
–
5
Typically, part of a portable computer.
Battery-powered device that uses radio waves or
infrared light waves.
Wireless, eliminates cord, frees up desk space
Types of Mouse Devices:
• Joystick
– The most popular input device for computer games.
– Controls game actions by varying pressure, speed, and
direction of the joystick.
– Can use buttons and triggers to specify commands or
initiate specific actions.
5
Types of Mouse Devices:
Related Devices
Trackball (roller ball) – control the pointer by rotating
a ball with your thumb
Touch surfaces – control the pointer by moving and
tapping your finger on the surface of a pad
Point stick - controls the pointer by directing the stick
with your finger. Located in the middle of the
keyboard.
5
Types of Mouse Devices:
•
Touch Screen Features
–
–
–
•
Light Pen Features
–
5
Behind the plastic layer of the touch screen are
crisscrossed invisible beams of infrared light.
Touching the screen with a finger can activate actions
or commands.
Touch screens are often used in ATMs, information
centers, restaurants, and or stores.
–
When the light pen is placed against the monitor, it
closes a photoelectric circuit.
The photoelectric circuit identifies the spot for
entering or modifying data.
SCANNING DEVICES
• Scanners copy or reproduce text as well as
images.
• Scanned data can be a written document, an
inventory tag, a price tag, a graphic image, or
even a photograph.
• A scanner device reads the data or
information and then converts it into a form
that the system unit can process.
5
Optical Scanners
• An optical scanner copies or reproduces text as well
as images.
• These devices record the light and dark areas as well
as color of the scanned document.
• After the image has been scanned, it can be
displayed, printed on paper, and stored for later uses.
• There are two basic types of scanners.
5
Optical Scanners
• Flatbed scanner – is much like a copy machine.
The image is placed on a glass surface. The
scanner records the image from below.
• Portable scanner – a handheld device that the user
slides across the image, making direct contact.
5
Bar-Code Reader
• Bar code readers identify the product
and search for a match in a computer
database.
• Supermarkets use bar-code reader
systems called the Universal Product
Code (UPC).
5
• A point-of-sale terminal will display the
price and name of the product.
Character and Mark Recognition
Device Features
• Can be used by mainframe computers or powerful
microcomputers.
• There are three kinds of character and mark
recognition devices:
• Magnetic-ink character recognition (MICR)
– Reads numbers on the bottom of checks.
• Optical-character recognition (OCR)
– Reads special preprinted characters, such as those on utility and
telephone bills. Example: Wand readers
5 • Optical-mark recognition (OMR)
– Reads marks on tests – also called mark sensing.
IMAGE CAPTURING DEVICES
• create or capture original images
• include digital cameras and digital video
cameras
• Digital Camera Features
– Images are recorded in the camera’s memory rather than on
film.
– You can take a picture and view it immediately.
– Prices are typically higher than regular cameras.
– Popular with real estate agents to capture pictures of homes
for Web pages.
5
IMAGE CAPTURING DEVICES
• Digital Video Camera Features
– Record motion digitally on a disk or in the camera’s
memory.
– The image quality is better and the price is higher than
traditional video cameras.
– Webcams are specialized digital video cameras that capture
images and send them to a computer for broadcast over the
Internet.
5
Digitizing Devices
• Convert a sketch or figure into a form that can
be processed by a computer.
• These devices have some type of flat surface
and a writing device.
• As the user moves the writing device across
the surface, the digitizing device records the
movement as a series of points and sends
this information to the computer.
• Two widely used digitizing devices are
graphic tablets and digital notebooks.
5
Graphic Tablets
• The item to be copied is placed on a flat
digitizing tablet.
• A special stylus connected to a computer is
used to trace the item.
• The computer records the position of the item
on the digitizing tablet.
• After the item is traced, its image can be
displayed on the screen, and printed or
stored in the computer.
5 • Graphic tablets are often used by designers,
architects, and engineers.
Digital Notebook Features
• Uses a special pen to write on a regular
notepad positioned on top of an
electronic pad or tablet.
• A signal from pen is sent to and stored
in the underlying electronic pad.
5
• Notes can be transferred to a
microcomputer to be viewed, edited or
printed.
AUDIO-INPUT DEVICES
5
•
Audio-input devices convert speech
into a digital code.
•
The most widely used audio-input
device is the microphone.
•
A microphone, sound card, and
software form a voice recognition
system.
Voice Recognition
System Features
5
•
Voice recognition systems can be used to operate
microcomputers or create documents.
•
Some voice recognition systems must be “trained”
to the particular user’s voice.
•
Training is done by matching the user’s spoken
words to previously stored patterns.
•
Advanced systems can recognize the same word
spoken by many different people.
•
Some systems can translate from one language to
another.
Voice Recognition
System Features
5
•
Portable systems can connect to a computer
system through system unit serial ports.
•
There are two types of voice recognition systems:
•
Discrete Speech – directly converts the spoken
word into printed material.
•
Continuous Speech – able to accept dictation as
well as spoken commands.
Discrete-Speech
Recognition Features
5
•
Common in business in preparing memos and
other written documents.
•
Widely used in legal and medical professions.
•
Audio signal is converted to a digital signal then
analyzed using a special program.
•
Program recognizes individual words based on
their sound and stores them in a file.
•
The system cannot distinguish between such
distinctions as they’re, their, and there. Captured
dictation must be reviewed to make corrections.
•
File can be retrieved, edited, and printed using a
standard word-processing program.
Continuous-Speech
Recognition Features
•
Key technology of the twenty-first century.
•
More natural and conversational than discrete word
systems.
•
Able to recognize individual words and phrases in
content.
•
Able to distinguish between same-sounding words
such as there, their, and they’re.
•
Can be used to accept commands to operate
applications such as Word and Excel.
5 •
Two well-known systems are NaturallySpeaking
from Dragon Systems and ViaVoice from IBM.
Output
• Output is people-readable information.
• Input (data) is processed inside the computer’s CPU
into meaningful output (information).
INPUT  PROCESSING  INFORMATION
• Output devices are any hardware used to provide or
to create output from the computer.
• Output devices translate the machine-readable
information into people-readable information.
5
Ouput
5
•
The three most widely used output devices
for microcomputers include:
•
Monitors - output images formed on a
screen.
•
Printers - output images formed on paper.
•
Audio system - output in form of sounds.
MONITORS
• Some monitors are used on the
desktop; others are portable.
• Two important characteristics of a
monitor are size and clarity.
5
Monitor Size
• A monitor’s size is indicated by the
diagonal length of its viewing area.
• Common sizes for monitors are 15, 17,
19, and 21 inches.
• Larger monitors can display more
information at one time.
5
• Larger monitors are more expensive.
Monitor Clarity
• A monitor’s clarity is indicated by its
resolution.
• Resolution is measured in pixels.
• Pixels are individual dots of picture elements
that form images on a monitor.
• The greater the resolution (more pixels), the
better the clarity of the image.
5
Monitor Standards
•
Standards have been created to indicate a
monitor’s color and resolution capabilities.
•
The four most common monitor standards
today are:
•
SVGA (Super Video Graphics Array)
–
–
•
XGA (Extended Graphic Array)
–
–
5
Has a minimum resolution of 800 by 600 pixels.
Primarily used with 15-inch monitors.
Has a resolution of 1024 by 768 pixels.
Popular today with 17-inch and 19-inch monitors.
Monitor Standards
•
SXGA (Super Extended Graphics Array)
–
–
•
UXGA (Ultra Extended Graphics Array)
–
–
–
5
Has a resolution of 1280 by 1024 pixels.
Popular with 19-inch and 21-inch monitors.
The newest and highest standard.
Popularity expected to increase with 21-inch monitor
use.
Primarily used for high end engineering design and
graphics arts.
Desktop Monitor - The
Cathode-Ray Tube (CRT)
•
The Cathode-Ray Tube (CRT) is the most common
type of monitor for home and office.
•
It is typically placed directly on the system unit or
desktop.
•
It is similar in size and technology to televisions.
•
The advantages of CRTs are low cost and excellent
resolution.
•
The disadvantage of CRTs is size.
5 •
Figure 5-19, page 127 shows a picture of a CRT
monitor.
Flat Panel Monitors
•
•
•
•
5
Also known as liquid crystal display (LCD)
monitors.
Uses a technology that involves liquid
crystals.
Are much thinner than CRTs.
Have been used for portable computers.
Flat Panel Monitors
• Passive-matrix (dual-scan monitor)
– Creates images by scanning the entire screen.
– Requires very little power.
– Clarity of image is not as sharp as active-matrix.
• Active-matrix
5
–
–
–
–
Does not scan down the screen to form images.
Each pixel is independently activated to form images.
More colors with better clarity can be displayed.
Are more expensive and require more power.
Other Monitors
• E-books are handheld, book-sized devices that
display text and graphics.
• The device uses special cartridges or the Web to
download content such as newspapers, magazines
and entire books.
• The cost of producing and distributing e-book content
is less than publishing and delivering traditional print
media.
• Many experts predict that e-books will soon become
as commonplace as today’s traditional books.
5
Other Monitors
• Data Projectors
– Data projectors are specialized devices similar to slide
projectors.
– These devices connect to microcomputers and project
computer output just as it would appear on a traditional
monitor.
– Data projectors are frequently used for to deliver
presentations created from presentation graphics
programs like PowerPoint.
5
Other Monitors
• HDTV is all-digital high-definition television (HDTV).
• HDTV delivers a clearer and more detailed widescreen picture.
• Digital output enables users to freeze video
sequence to create still images.
• Frozen images can be digitized and output as artwork
or stored on disks.
5
• This technology is useful to graphic artists,
publishers, and educators.
PRINTERS
•
Three popular kinds of printers used
with microcomputers are:
•
Ink-Jet – the most widely used printer.
–
5
–
–
–
Sprays small droplets of ink at high speed
onto the surface of the paper.
Produces a letter-quality image.
Permits printing in a variety of colors.
Reliable, quiet, and inexpensive.
PRINTERS
•
Laser – used in applications requiring highquality output.
–
–
–
–
Uses a technology similar to that used in
photocopying machines (laser beam).
Produces images with excellent letter and graphics
quality.
More expensive than ink-jet printers.
There are two categories of laser printers:
•
5
•
Personal – inexpensive and used by many single users. (4-6
pages a minute)
Shared – more expensive and shared by a group of users.
(over 30 pages a minute)
PRINTERS
•
Thermal – widely used to produce very
high quality color artwork and text.
–
–
–
5
Uses heat elements to produce images on
heat-sensitive paper.
Not as popular because of cost and
requirement of specially treated paper.
Produces near-photographic output.
Other types of printers:
• Dot Matrix
5
– Was once the most widely used microcomputer
printer.
– Forms characters or images using a series of
small pins on a print head.
– Are inexpensive and reliable, but noisy.
– Often used for draft documents or documents
that will not be shown to customers.
Printers
• Chain
– Designed to serve minicomputers, mainframes, and
communications networks.
– Expensive, high-speed machines
• Plotters
5
– Special-purpose output devices
– Used to produce charts, maps, architectural drawings,
and 3-D illustrations
– Produce high-quality multicolor documents or larger
size documents
AUDIO-OUTPUT DEVICES
–
–
–
–
–
–
5
–
Audio-output devices translate audio information
from the computer into sounds that people can
recognize and understand.
Audio-output devices use prerecorded vocalized
sounds to produce output.
Most widely used audio-output devices are stereo
speakers and headphones.
Devices are connected to a sound card in the system
unit.
Sound card is used to capture sound as well as play it
back.
Voice output is not as difficult to create as voice
input.
The computer “speaks” synthesized words.
AUDIO-OUTPUT DEVICES
•
5
Examples of voice output uses:
– Soft-drink machines, the telephone, and in
cars.
– Voice output can be used as a tool for
learning.
– Can help students study a foreign language
– Used in supermarkets at the checkout counter
to confirm purchases
– Most powerful capability is to assist the
physically challenged
COMBINATION INPUT AND
OUTPUT DEVICES
•
Fax Machine Features
–
–
–
–
5
–
Fax machines are also called facsimile transmission
machines.
In transmission, the sending fax converts the image to
a format for telephone lines.
The receiving fax then converts the telephone format
back to its original image.
Dedicated fax machines are stand-alone devices for
sending and receiving images over telephone lines.
Most computers systems now have fax/modem
boards that provide fax and modem capabilities.
COMBINATION INPUT AND
OUTPUT DEVICES
• Multifunctional devices
5
– Multifunctional devices have input and output
capabilities such as scanner, fax, and copying
machine.
– These devices offer a cost and space advantage.
– Disadvantage of these systems is the quality
and functionality is not quite as good as
separate function devices.
– Multifunctional devices are widely used in
home and small business offices.
COMBINATION INPUT AND
OUTPUT DEVICES
• Internet Telephone
5
– Internet telephony, also known as telephony,
uses the Internet to connect two or more people
via telephone.
– This requires the Internet, a special service
provider, a sound card, and special software.
– This service is not available in all locations but
is gaining in popularity.
COMBINATION INPUT AND
OUTPUT DEVICES
• Terminals
– A terminal is an input and output device that
connects you to a mainframe called a host
computer or server.
– There are four kinds of terminals: Dumb,
Intelligent, Network and Internet.
5
COMBINATION INPUT AND
OUTPUT DEVICES
• Dumb Terminal
– Used to input and receive data only.
– It cannot process data independently.
– A terminal used by an airline reservation clerk
to access a mainframe computer for flight
information is an example of a dumb terminal.
5
COMBINATION INPUT AND
OUTPUT DEVICES
• Intelligent Terminal
5
– Includes a processing unit, memory, and secondary
storage.
– It uses communications software and a telephone
hookup or other communications link.
– A microcomputer connected to a larger computer by a
modem or network link is an example of an intelligent
terminal.
– An increasingly popular type is the Net PC. These lowcost and limited microcomputers typically have only
one type of secondary storage, a sealed system unit, and
no expansion slots.
COMBINATION INPUT AND
OUTPUT DEVICES
• Network Terminal
5
– Also known as a thin client or network
computer.
– It is a low cost alternative to an intelligent
terminal.
– Most network terminals do not have a hard
drive.
– This type of terminal relies on a host computer
or server for application or system software.
COMBINATION INPUT AND
OUTPUT DEVICES
• Internet Terminal
– Is also known as a Web terminal or Web
appliance.
– It provides access to the Internet and displays
Web pages on a standard television set.
– It is used almost exclusively in the home.
5