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5. CHAPTER. Input and Output. 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.

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Input and Output

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  • 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.

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  • 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.

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  • 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.

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  • 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).

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  • 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.

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  • 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.

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  • 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.

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

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  • 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.

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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.

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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.

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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

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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.

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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.

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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.

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  • 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.

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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.

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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.

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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.

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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.

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  • 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.

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  • 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.

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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.

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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.

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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.

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  • 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.

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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.

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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.

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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.

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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.

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  • Output is people-readable information.

  • Input (data) is processed inside the computer’s CPU into meaningful output (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.

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  • 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.

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

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

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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  • 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.

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  • 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)

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  • 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.

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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.

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  • 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

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  • 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.

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  • 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

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  • 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.

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  • 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.

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  • 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.

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  • 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.

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  • 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.

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  • 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.

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  • 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.

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  • 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.