Learning Objectives • Identify several types of input and output devices and explain their functions. Chapter 5 • Describe the characteristics of the input equipment that most users encounter regularly, Input and Output namely, keyboards and pointing devices. • Explain what source data automation is and discuss how scanners and other devices can be used to accomplish it. Learning Objectives, cont’d. Overview • This chapter covers: • List several types of multimedia input devices and discuss their purposes. – Equipment designed primarily for input of • Describe the characteristics of the output equipment that programs and data into the computer most users encounter regularly, namely, display devices system, or for output, or for both. and printers. • Many other types of input/output devices • Discuss several types of multimedia output equipment. exist, but this chapter covers a good • Explain what a multifunction device is and list some sampling of the most widely used ones. advantages and disadvantages of using such a device. Input and Output Keyboards • Keyboards can differ in number of keys, key • Input devices convert data and programs that arrangement, types of special keys, and touch. people can understand into a form – QWERTY – widely used comprehensible to the CPU. – Dvorak – not used often • Output devices convert the strings of bits used • Function keys enable software packages to be by the computer back into a form that people customized to meet a user's applications needs. can understand. • The numeric keypad makes it easy to enter numbers quickly. 1 Ergonomic Keyboards • Designed to reduce or minimize repetitive strain injury of wrists – Provide more natural, comfortable position of wrists, arms, and hands Pointing Devices: Mouse • The most common pointing device – Movement on flat surface causes Common mouse movement of pointer on screen operations are clicking, • Several types scrolling, and dragging – Mechanical - small ball on underside rolls as and dropping. mouse is moved – Optical - uses a light beam to monitor mouse movement – Cordless - uses either infrared or radio waves, rather than a cord, to connect to computer Pointing Devices: Electronic Electronic Pens Use Pens • Electronic pen: an alternative to the mouse to • Graphics tablet select objects or to write or draw on the screen – User moves stylus or puck • Types: across board – light pen (uses light-sensitive cell in its tip) – Used to create or trace precise – stylus (usually plastic) drawings • Devices that use pen input: • • Pen-based computing – Signature capture devices –Use pen-like stylus to input data – Graphics tablets –Often used in PDAs or pocket PCs – Pen-based computers –Use handwritten character recognition 2 Pointing Devices: Touch Screens Trackball and Joystick • Touch screens are used: • Trackball – When consumer input is – Variation on mechanical mouse required, as in consumer kiosks – User rolls the ball directly – When other input devices are – Often built into laptop computers impractical • Joystick – Allow user to touch items on – Short lever with handgrip screen – Distance and speed of movement – Position of finger on screen controls pointer’s position determines item to be input – Pressing trigger causes actions to into system take place Touchpad and Pointing Stick Scanners and Related Devices • Touchpad • Source data automation involves collecting – Rectangular pressure-sensitive pad data in machine-readable form as soon as – Sliding finger across pad moves pointer it is generated. – Tapping with finger recognized as click • Pointing stick • Source data automation is used to convert – Small pressure-sensitive post source documents into digital form and mounted in center of keyboard commonly utilizes some type of scanner. – Pushing post in any direction moves pointer Optical Scanners Scanners • Flatbed scanner • Optical scanner: converts hard-copy images of • – Typically scans one page at a text pages, photographs, and drawings into time digital form – Can be used to scan large bound documents • Common uses: • Sheetfed scanner – Scanners at supermarkets – Motorized rollers feed sheet – Document imaging - converts paper across scanner head documents to electronic versions • Handheld scanner • Documents stored on disk – Smallest and least accurate • Can be edited or processed by software 3 Scanners (Cont’d) Optical Readers • Other types of scanners: – Drum scanner (very large and expensive. • Optical marks Documents are mounted on a glass cylinder) – 3D scanner (for multimedia applications) • Optical • Scanner resolution • characters – Measured in dots per inch (dpi) – 72 to 150 dpi for images displayed on screen Optical codes – 300 dpi and higher for printed • Optical codes Magnetic Ink Character Optical Characters Recognition (MICR) •Optical character recognition (OCR) software required to convert picture (scanned document) into • Uses a machine to read characters characters made of •2nd type of optical character recognition magnetized particles –Wand reader reads characters in special typeface • Banking industry is • Bar Codes predominant user – A series of vertical marks – Characters preprinted on lower left-hand side of check – Represents a unique code – Amount added by MICR • Universal Product Code (UPC) inscriber when check is used as standard in supermarkets cashed Magnetic Ink Character Recognition Multimedia Input: Digital Reader Cameras • Readers can read the special magnetic • User takes photo that is stored on a chip characters, as well as sort documents by their instead of film codes. • Photos can be downloaded to computer (via cable or special card reader) – Use photo-editing software to enhance – Store permanently on CDs or DVDs • Photos composed of many pixels of color • Photos stored on removable memory card 4 Multimedia Input: Video Cameras • Video cameras can be used to either record or send images over the Internet. • Video input can also be obtained by using special hardware to transfer conventional video images to the computer. Multimedia Input: Video Input Audio Input Devices • Digital video consists of series • Voice-input systems convert spoken words to digital of still frames data. – Displayed rapidly enough to • User speaks to computer give illusion of motion – Speech recognition devices convert spoken words into binary digits • Web cam used to transmit binary digits • Most are speaker-dependent video over the Internet • – System “learns” user’s voice • Can capture video from • Types of systems analog sources with video – Discrete word systems - user must pause between capture card words – Continuous word systems - user can speak normally Other Audio Input Devices Display Devices • Music-input systems can record musical input for • Display devices are the most common type of use with a multimedia presentation or to be output device. edited or combined with other input • PC displays are commonly called monitors. • MIDI – musical instrument digital interface – device, such as musical keyboard • Can be separate from computer or combined • Telephony is the process of performing telephone-oriented tasks using a computer • The cursor, or insertion point, indicates where editing or typing will appear on the display screen. 5 Size Resolution • Resolution refers to the sharpness of the screen image. • Most monitors today are about 17 inches screen image. wide, measured diagonally. Images are formed by lighting up tiny • The actual viewing area is typically less dots on the screen called pixels. than the stated size. Resolution (cont’d) Graphics Standards • Dot pitch – the distance between the pixels • Computer graphics standards specify such characteristics (measures in millimiters). Usual are .26 and .28 as the possible resolutions and number of colors that can (smaller is better) be used. • Resolution shows how many distinct columns • Video cards connect the monitor to the PC and support a and rows of pixels the screen can display particular graphics standard, such as SVGA. (SVGA allows true color - 24 bit - 16.7 million colors) • Higher resolution – smaller image – more details • • Video cards typically contain video RAM to support the number of colors and resolutions allowed, as well as to • Can be selected by user help speed up image display. Color vs. Monochrome Displays CRT vs. Flat-Panel Displays • Most color displays are of the RGB type. • Most desktop display devices use CRT • RGB displays combinations of red, blue, and cathode ray tube) technology, similar to green light to form other colors. green light to form other colors. conventional television technology. • Refresh rate – 60 to 80 times per second (Hz) • Flat-panel displays are compact, lightweight, and consume little power. – Ideal for notebook computers – Most use liquid crystal display (LCD) technology 6 Flat-Panel Screens Flat Panel Technologies • Active-matrix LCD • Liquid crystal display (LCD) – Uses many thin-film transistors (TFT) – Originally used for laptops, but – Produces brighter image and can be viewed from wider angles making their way to desktop Passive-matrix LCD computers • Passive-matrix LCD – Uses fewer transistors • Very thin (only a few inches) – Cheaper and uses less power • Produce sharper text images • Gas plasma than CRTs – Supports very large displays – Has brilliant color display • Easier on eyes than CRTs – Viewable at very wide angles HDTV • HDTV is a new type of television that supports high-resolution digital broadcasts (up to 1080 lines) • Wide-format (16:9 instead of regular 4:3) • All broadcasting is