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Information and Communication Technology Fundamentals Credits Hours: 2+1 Instructor: Ayesha Bint Saleem Input Devices Presentation Credits • “Introduction to Computer” by Peter Norton • “Using Information Technology” by Williams and Sawyer • “Introduction to Information Technology” by V. Rajaraman Input & Output •Input hardware - devices that translate data into a form the computer can process •Output hardware - devices that translate information processed by the computer into a form that humans can understand The Keyboard • The most common input device • Must be proficient with keyboard • Skill is called keyboarding • Alphanumeric keys • Modifier Keys • Numeric keypad • Function Keys • Cursor Movement keys • Special Purpose keys 3A-5 The Keyboard • How keyboard works • Keyboard controller detects a key press • Corresponding code held temporarily in Keyboard buffer • Controller signals system software • System software • fetches code from keyboard buffer • Passes on to the CPU • Controller repeats the letter if held 3A-6 The Keyboard •Traditional computer keyboards •Typewriter style + special keys •Connect to computer •Via wires •wirelessly •Specialty keyboards and terminals • Dumb terminals • • Intelligent terminals Internet terminals Pointing Devices •Pointing devices control the position of the cursor or pointer on the screen • • • • Mouse Trackball Pointing stick Touchpad Mouse for a right-handed user The Mouse • All modern computers have a variant • Allows users to select objects • Pointer moved by the mouse • Mechanical mouse • Rubber ball moves • Rollers send information about speed and direction to system software • The ball often requires cleaning 3A-9 The Mouse • Optical mouse • Light shown onto mouse pad • Reflection determines speed and direction • Requires little maintenance 3A-10 The Mouse • Interacting with a mouse • Actions involve pointing to an object • Clicking selects the object • Clicking and holding drags the object • Releasing an object is a drop • Right clicking activates the shortcut menu • Modern mice include a scroll wheel 3A-11 The Mouse • Benefits • Pointer positioning is fast • Menu interaction is easy • Users can draw electronically 3A-12 Variants of the Mouse • Trackballs • Upside down mouse • Hand rests on the ball • User moves the ball • Uses little desk space 3A-13 Variants of the Mouse • Track pads • Stationary pointing device • Small plastic rectangle • Finger moves across the pad • Pointer moves with the pointer • Popular on laptops 3A-14 Variants of the Mouse • Track point • Little joystick on the keyboard • Move pointer by moving the joystick 3A-15 Inputting Data In Other Ways Devices for the Hand • Pen based input • Tablet PCs, PDA • Pen used to write data • Pen used as a pointer • Handwriting recognition • On screen keyboard 3B-17 Devices for the hand • Touch screens • video display screen that has been sensitized to receive input from the touch of a finger • Sensors determine where finger points • Sensors create an X,Y coordinate • Usually presents a menu to users • Work well in dirty environments like auto garages and restaurants 3B-18 Devices for the hand • Game controllers • Enhances gaming experience • Difficult maneuvering with mouse and keyboard • Provide custom input to the game • Modern controllers offer feedback • Joystick • Game pad 3B-19 Optical Input Devices • Allows the computer to see input • Bar code readers • Converts bar codes to numbers • UPC code • Computer find number in a database • Works by reflecting light • Amount of reflected light indicates number • Special bars on the edges of the UPC indicate start and end of product 3B-20 Optical Input Devices • Image scanners • Converts printed media into electronic • Reflects light off of the image • Sensors read the intensity • Filters determine color depths Flat Bed Scanner Image Courtesy: www.itreviews.co.uk 3B-21 Optical Input Devices • Flat Bed Scanners (example of black and white image scanning) • Optical System consisting of • Light beam • Lens • Mirrors • Array of solid state “electronic eyes” • Charged Coupled Devices (CCD) • Sense light and give electrical output • Electrical o/p depends on intensity of light 3B-22 Optical Input Devices • Flat Bed Scanners • Electronic Circuit • Converts electrical output to set of bits • Stored in computer memory • Document to be scanned placed over flat glass of scanner • Light focused on an entire line as a thin beam – scan line • Light reflected from paper along scan line • Light gathered by Electronic Eyes (CCD) 3B-23 Optical Input Devices • Flat Bed Scanners • Dark spots not reflecting light stored as 0s • White spots reflecting light stored as 1s • 300 CCs per inch on a horizontal line • 300 bits per inch resolution • Light source moved to next scan line • Number of scan lines in Y-direction determined by mechanical precision of motor moving light beam 3B-24 Optical Input Devices • Flat Bed Scanners • Usually double the horizontal resolution • 300 bits/inch 600 scan lines per inch • Each reflected light beam picked up by CCD is called ‘picture element’, pixel or pel • 300 CCD elements/inch in X-direction • 600 scan lines/inch in Y direction • 300 x 600 = 180000 pixels per square inch • Bitmap form • A4 with 7”x9” printed/text area • 7 x 300 x 9 x 600 bits = 11.34 Megabits • 1.14175 MB 3B-25 Optical Input Devices • Flat Bed Scanners • Information on paper pure text • 80 char/line, 24 lines/page 1920 characters • 1920 bytes needed to store entire page if ASCII code is used • Information on paper handwriting/image • Two-tone picture 3B-26 Optical input devices • Optical character recognition (OCR) • Converts scanned text into editable text • Each letter is scanned • Letters images are compared to known images of letters • After letters are recognized, word is formed • Word is matched with words stored in dictionary • Nearest matching word from dictionary is selected • Rarely 100% accurate • Accuracy depends on • Recognition method • Size of dictionary 3B-27 Optical input devices • Acquisition of multitone pictures White 00 Light Grey Dark Grey 01 10 Black 11 • 2 bits used per pixel 4 shades of grey • 4 bits/pixel 24 = 16 shades of grey • CCD array senses light intensities and converts them to equivalent bit strings • Number of levels of intensity sensed by CCD determines its capability to represent grey levels • 8 bits/pixel 28 = 256 shades of grey • Storage requirement 8 x as compared to using 1 bit • 9.134 MB 3B-28 Optical input devices • Acquisition of color pictures • Red, Green, Blue – primary colors • Our eyes perceive different colors by adding these primary colors in different proportions • In color scanning, principle is to measure the intensity of RGB colors reflected by picture element • RGB components in reflected light are found by rapidly rotating disk which has RGB filters and picking up RGB components separately 3B-29 Optical Input Devices Resolution: Number of pixels in an image High resolution image Image Courtesy: www.intothelimelight.co.za/thingstoknowtext.htm Low resolution image Optical input devices • Acquisition of color pictures (fig on board) • The intensity of each component is measured by a CCD to 8 significant bits (in most scanners) • If R, G, B are combined we have 24 bits to represent different colors • 224 = 16 million colors can be represented • 24 times the size of black and white picture • 3 times the size of 256-level grey scale picture • 27.402 MB 3B-31 Image Compression • To reduce the size of an image so that it occupies less storage space and less bandwidth for communication • Different Techniques exist • GIF • JPEG • Compression ratio • For color images if we can somehow get 8 bits/pixel instead of 24 bits/pixel we have compression ratio of 1:3 Audiovisual Input Devices • Digital cameras • Captures images electronically • No film is needed • Image is stored as a JPG file • Memory cards store the images • Used in a variety of professions 3B-33 Audiovisual Input Devices • Microphones • Used to record speech • Convert sound waves to electrical signal • Sound Card • Digitizes electrical signals Audio Signal Analog to Digital Converter Storage • Some explanation on board 3B-34 Audiovisual Input Devices • Speech recognition • “Understands” human speech • Allows dictation or control of computer • Matches spoken sound to known phonemes • 40 phonemes in English Language • Matching still difficult – two vs too • Context to be taken into account • Large stored vocabularies of spoken words • Enters best match into document • Users may train the software • Older systems required the user to pause between words • Newer systems can recognize continuous speech 3B-35 Audiovisual Input Devices • Musical Instrument Digital Interface • MIDI • Connects musical instruments to computer • Digital recording or playback of music • Musicians can produce professional results 3B-36 Audiovisual Input Devices • Acquisition of video • Webcam • Camcorders • Aspect ratio – 4:3 • Persistence of vision • Sequence of Image frames taken at a rate of 30 frames per second • High storage and transmission requirements 3B-37