55

5555CH

AP

TE

R

Input and Output

55

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.

• To understand that output devices translate machine output to output people can comprehend.

55

• Input is any data or instructions that are used by a computer.

• It can come directly from the user or from other sources.

• You can enter data and issue commands using your keyboard, voice, by pointing to items, and by writing on special devices.

Input

55

• Input devices are hardware devices that convert people-readable data into machine-readable 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.

Input

55

• 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).

Input

55

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.

• Traditional, ergonomic, and folding are types of keyboards.

55

Keyboards

• Numeric Keypad - Enters numbers, arithmetic symbols, controls cursor or insertion point.

• Function Keys - Shortcut for specific tasks such as F1 for online Help.

• Escape Key - Typically cancels a selection or a procedure.

• Windows Key - Displays the Start menu.

55

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 another key – Ctrl, Alt, Shift.

55

Keyboards

• Special Keys - Keys above arrow keys to the right of keyboard.

55

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.

• Direct entry includes pointing, scanning, and voice-input devices.

55

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.

55

Types of Mouse Devices:• Mechanical Mouse

– Has a ball on the bottom and is attached to the system unit with cable.

– Controls the pointer when rolled on a tabletop.

• Optical Mouse– 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.

55

Types of Mouse Devices:• Cordless Mouse

– Typically, part of a portable computer.– Battery-powered device that uses radio waves or

infrared light waves.– Wireless, eliminates cord, frees up desk space

55

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.

55

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.

55

Types of Mouse Devices:• Touch Screen Features

– 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.

• Light Pen Features– 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.

55

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.

55

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.

55

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.

55

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).

• A point-of-sale terminal will display the price and name of the product.

55

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

• Optical-mark recognition (OMR)– Reads marks on tests – also called mark sensing.

55

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.

55

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.

55

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.

55

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.

• Graphic tablets are often used by designers, architects, and engineers.

55

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.

• Notes can be transferred to a microcomputer to be viewed, edited or printed.

55

AUDIO-INPUT DEVICES

• 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.

55

Voice Recognition System Features• 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.

55

Voice Recognition System Features• 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.

55

Discrete-Speech Recognition Features• 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.

55

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.

• Two well-known systems are NaturallySpeaking from Dragon Systems and ViaVoice from IBM.

55

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.

55

Ouput

• 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.

55

MONITORS

• Some monitors are used on the desktop; others are portable.

• Two important characteristics of a monitor are size and clarity.

55

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.

• Larger monitors are more expensive.

55

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.

55

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)– Has a minimum resolution of 800 by 600 pixels.– Primarily used with 15-inch monitors.

• XGA (Extended Graphic Array)– Has a resolution of 1024 by 768 pixels.– Popular today with 17-inch and 19-inch monitors.

55

Monitor Standards• SXGA (Super Extended Graphics Array)

– Has a resolution of 1280 by 1024 pixels.

– Popular with 19-inch and 21-inch monitors.

• UXGA (Ultra Extended Graphics Array)– The newest and highest standard.

– Popularity expected to increase with 21-inch monitor use.

– Primarily used for high end engineering design and graphics arts.

55

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.

• Figure 5-19, page 127 shows a picture of a CRT monitor.

55

Flat Panel Monitors• 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.

55

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– 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.

55

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.

55

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.

55

Other Monitors

• HDTV is all-digital high-definition television (HDTV).

• HDTV delivers a clearer and more detailed wide-screen 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.

• This technology is useful to graphic artists, publishers, and educators.

55

PRINTERS • Three popular kinds of printers used

with microcomputers are:

• Ink-Jet – the most widely used printer.– 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.

55

PRINTERS • Laser – used in applications requiring high-

quality 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:• 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)

55

PRINTERS • Thermal – widely used to produce very

high quality color artwork and text.– 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.

55

Other types of printers:

• Dot Matrix– 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.

55

Printers

• Chain– Designed to serve minicomputers, mainframes, and

communications networks.– Expensive, high-speed machines

• Plotters – Special-purpose output devices – Used to produce charts, maps, architectural drawings,

and 3-D illustrations– Produce high-quality multicolor documents or larger

size documents

55

AUDIO-OUTPUT DEVICES – 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.

55

AUDIO-OUTPUT DEVICES• 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

55

COMBINATION INPUT AND OUTPUT DEVICES • Fax Machine Features

– 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.

55

• Multifunctional devices– 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

55

• Internet Telephone– 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

55

• 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.

COMBINATION INPUT AND OUTPUT DEVICES

55

• 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.

COMBINATION INPUT AND OUTPUT DEVICES

55

• Intelligent Terminal– 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 low-cost and limited microcomputers typically have only one type of secondary storage, a sealed system unit, and no expansion slots.

COMBINATION INPUT AND OUTPUT DEVICES

55

• Network Terminal– 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

55

• 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.

COMBINATION INPUT AND OUTPUT DEVICES