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

Copyright © Exclusive rights by The McGraw-Hill Companies, Inc. 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

3A-5 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-6 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

Copyright © Exclusive rights by The McGraw-Hill Companies, Inc. Traditional computer keyboards Typewriter style + special keys Connect to computer Via wires wirelessly Specialty keyboards and terminals Dumb terminals Intelligent terminals Internet terminals The Keyboard

Copyright © Exclusive rights by The McGraw-Hill Companies, Inc. 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

3A-9 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-10 The Mouse Optical mouse Light shown onto mouse pad Reflection determines speed and direction Requires little maintenance

3A-11 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-12 The Mouse Benefits Pointer positioning is fast Menu interaction is easy Users can draw electronically

3A-13 Variants of the Mouse Trackballs Upside down mouse Hand rests on the ball User moves the ball Uses little desk space

3A-14 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-15 Variants of the Mouse Track point Little joystick on the keyboard Move pointer by moving the joystick

Inputting Data In Other Ways

3B-17 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-18 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-19 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-20 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-21 Optical Input Devices Image scanners Converts printed media into electronic Reflects light off of the image Sensors read the intensity Filters determine color depths Image Courtesy: Flat Bed Scanner

3B-22 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-23 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-24 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-25 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 = pixels per square inch Bitmap form A4 with 7”x9” printed/text area 7 x 300 x 9 x 600 bits = Megabits MB

3B-26 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-27 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-28 Optical input devices Acquisition of multitone pictures 2 bits used per pixel  4 shades of grey 4 bits/pixel  2 4 = 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  2 8 = 256 shades of grey Storage requirement 8 x as compared to using 1 bit MB White 00 Light Grey 01 Dark Grey 10 Black 11

3B-29 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

Optical Input Devices Image Courtesy: Resolution: Number of pixels in an image Low resolution imageHigh resolution image

3B-31 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 2 24 = 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 MB

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

3B-33 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-34 Audiovisual Input Devices Microphones Used to record speech Convert sound waves to electrical signal Sound Card Digitizes electrical signals Some explanation on board Audio Signal  Analog to Digital Converter  Storage

3B-35 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-36 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-37 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