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INPUT DEVICES

INPUT DEVICES. Keyboard • Common input device • Standardized layout (QWERTY) (although non-alphanumeric keys are placed differently, and there is a difference between key assignments on UK and USA keyboards) QWERTY arrangement not optimal for typing - layout due to typewriters.

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INPUT DEVICES

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  1. INPUT DEVICES

  2. Keyboard • Common input device • Standardized layout (QWERTY) (although non-alphanumeric keys are placed differently, and there is a difference between key assignments on UK and USA keyboards) QWERTY arrangement not optimal for typing - layout due to typewriters. Other keyboard designs allow faster typing but large social base of QWERTY typists produces reluctance to change. • Key press closes connection, causing a character code to be sent • Usually connected by an umbilical cord • Allows rapid entry of text by experienced users

  3. Other Keyboards Alphabetic Keys arranged in alphabetic order • not faster for trained typists • not faster for beginners either

  4. Keyboards, Cont’d • Can be: • Wireless • Portable • Foldable • Handheld PCs and mobile devices today often have a built-in keyboard or thumb pad (keyboard designed to be pressed with just the thumbs)

  5. Pointing devices • Mouse • Light Pen / Stylus • Touch Screen

  6. Positioning and Pointing Devices MouseHandheld pointing device • very common • easy to use Two characteristics • planar movement • buttons (usually from 1 to 3 buttons on top, used for making a selection, indicating an option, or to initiate drawing etc.)

  7. Mouse cont…. Mouse located on desktop • requires physical space • no arm fatigue Relative movement only is detectable. Movement of mouse moves screen cursor Screen cursor oriented in (x, y) plane,mouse movement in (x, z) plane: an indirect manipulation device. Device itself doesn’t obscure screen, is accurate and fast. Can lead to hand-eye coordination problems due to indirectness of manipulation.

  8. How does it work? Two methods for detecting motion Mechanical Ball on underside of mouse turns as mouse is moved Rotates orthogonal potentiometers Can be used on almost any flat surface

  9. Optical • light emitting diode on underside of mouse • detects fluctuating alterations in reflected intensity as mouse is moved over the gridlines, used to calculate relative motion in (x, z) plane

  10. Other Pointing Devices • Joysticks • Trackballs • Pointing sticks • Touch pads

  11. Other positioning devices • Joystick • Indirect device • Takes up very little space • Controlled by either • • movement (absolute joystick) - position of joystickcorresponds to position of cursor • • pressure (isometric or velocity-controlled joystick) - pressure on stick corresponds to velocity of cursor • Usually provided with buttons (either on top or on front like a trigger) for selection • Does not obscure screen • Inexpensive (often used for computer games, also because they are more familiar to users)

  12. Trackball Bit like an upside-down mouse. Ball is rotated inside static housing, relative motion moves cursor. Indirect device, fairly accurate. Requires buttons for picking. Size and “feel” of trackball itself important. Requires little space, becoming popular for portable and notebook computers.

  13. Touch-sensitive screen (touchscreens) Detect the presence of finger or stylus on the screen. Work by interrupting matrix of light beams or by capacitance changes or ultrasonic reflections. Direct pointing devices. Advantages: Fast, and require no specialised pointer. Good for menu selection. Suitable for use in hostile environment: clean and safe from damage. Disadvantages: Finger can mark screen. Imprecise (finger is a fairly blunt instrument!) - difficult to select small regions or perform accurate drawing. Lifting arm can be tiring, and can make screen too close for easy viewing.

  14. The user can point, tap, draw and write on the computer’s screen with a pen.

  15. Other text entry devices Handwriting recognition Handwritten text can be input into the computer, using a pen and a digesting tablet • common form of interaction Problems in • capturing all useful information - stroke path, pressure, etc. in a natural manner • segmenting joined up writing into individual letters • interpreting individual letters • coping with different styles of handwriting Handheld organizers being released now that incorporate handwriting recognition technology and do away with a bulky keyboard

  16. Light pen Coiled cable connects pen to c.r.t. In operation, pen held to screen and detects burst of light from screen phosphor during display scan. Direct pointing device: accurate (can address individual pixels), so can be used for fine selection and drawing. Problems: pen can obscure display, is fragile, can be lost on a busy desk, tiring on the arm. Both much less popular than the mouse

  17. Electronic Pens • Electronic pen (stylus or digital pen): used instead of a mouse to select objects, as well as to draw or write electronically on the screen • Commonly used with pen-based PCs • To issue commands and input data • If handwriting recognition is used, written text can be converted to editable typed text

  18. Digitizing tablet Indirect device. Resistive tablet detects point contact between 2 separated sheets: has advantages in that it can be operated without specialised stylus - a pen or the user’s finger is fine. Magnetic tablet detects current pulses in magnetic field using small loop coil housed in special pen. Also capacitive and electrostatic tablets. Sonic tablet similar to above but requires no special surface: ultrasonic pulse emitted by pen detected by two or more microphones which then triangulate the pen position.   Can also be used for text input (if supported by character recognition software). Require large amount of desk space, and may be awkward to use if displaced by the keyboard.

  19. Electronic Pens, Cont’d • Also used with • Digital writing systems • Graphics tablets • Signature capture devices

  20. Data glove Lycra glove with optical fibre sensors. Detects joint angles and 3-d hand position. Solution in search of a problem - the technology to utilise the power of this form of input properly does not exist yet. Advantages: easy to use, potentially powerful and expressive (10 joint angles + 3-d. spatial information, at 50 Hz.). Disadvantages: difficult to use with a keyboard, expensive (~£10k/glove). Potential: vast - gesture recognition, sign language interpretation, etc. Eyegaze Headset detects user’s eye movements to control cursor. Very fast and accurate, also expensive.

  21. Alternative Input Devices – Optical Input Devices • Bar Code Readers • Image Scanners and OCR

  22. Optical Input Devices - Bar Code Readers • Bar code readers can read bar codes—patterns of printed bars. • The reader emits light, which reflects off the bar code and into a detector in the reader. The detector translates the code into numbers. • Flatbed bar code readers are commonly found in supermarkets. Courier services often use handheld readers.

  23. Bar code readers commonly tracksales in retail stores

  24. Optical Input Devices – Image Scanners and OCR • Image scanners digitize printed images for storage and • manipulation in a computer. • A scanner shines light onto the image and interprets the reflection. • Optical character recognition (OCR) software translates scanned text into editable electronic documents.

  25. Document being scanned Converts diode signals to numbers To computer Light source, lens and diode array

  26. Scanners and Optical Character Recognition Scanners take paper and convert it into a bitmap Two sorts of scanner • flat-bed: paper placed on a glass plate, whole page converted into bitmap • hand-held: scanner passed over paper, digitising strip typically 3-4” wide Can work in colour: shine light at paper and note intensity of reflection. Resolutions from 300-600 dpi, but available up to 4800 dpi. Also special scanners for slides and photographic negatives

  27. Scanners cont Used in • desktop publishing for incorporating photographs and other images • used in document storage and retrieval systems, doing away with paper storage Optical character recognition (OCR) converts bitmap back into text • different fonts create problems for simple “template matching” algorithms • more complex systems segment text, decompose it into lines and arcs, and decipher characters that way

  28. Readers, Cont’d • Radio frequency identification (RFID) readers • Radio frequency identification (RFID): technology used to store and transmit data located in RFID tags • RFID tag: device containing tiny chips and radio antennas that is attached to objects that will be identified using RFID technology • Applications: tracking inventory pallets and shipping containers, tracking or locating livestock and other animals, tagging tractors and other large assets to keep track of their locations

  29. Readers, Cont’d • Optical mark readers (OMRs):input data from special forms to score or tally exams, questionnaires, ballots, and so forth • Use pencil to fill in small circles/shapes on the form to indicate their selections • Forms are inserted into an optical mark reader to be scored or tallied

  30. Readers, Cont’d • Magnetic ink character recognition (MICR) readers: read MICR characters • Used primarily for banking • MICR readers read the special magnetic characters and sort/processchecks

  31. Alternative Input Devices – Audio-Visual (Multimedia) Input Devices • Microphones and Speech Recognition • Video Input

  32. Audio-Visual (Multimedia) Input Devices - Microphones and Speech Recognition • Microphones can accept auditory input. A microphone requires a sound card in the PC. • A sound card can digitize analog sound signals, and convert digital sound signals to analog form. • With speech recognition software, you can use your microphone to dictate text, navigate programs, and choose commands.

  33. Analog Sound Signals Digital Audio Output [electrical signals] (ex. 11100011) to computer Analog Signals are Digitized

  34. Speech recognition Promising, but only successful in limited situations - single user, limited vocabulary systems Problems with • external noise interfering • imprecision of pronunciation

  35. Audio Input • Audio input:process of entering audio data into the computer (voice and music) • Voice input systems (speech recognition systems): enable a computer to recognize the human voice • Consist of a microphone or headset and appropriate software • Can be used to dictate text or commands into a PC • Music input systems: can input and record music (either original compositions or via a CD or DVD player)

  36. Audio Input, Cont’d

  37. Audio-Visual (Multimedia) Input Devices – Video Input • PC video cameras digitize full-motion images. • Digital cameras capture still images. • These cameras break images into pixels and store data about each pixel. • Video images may be compressed to use less memory and storage space.

  38. Readers, Cont’d • Biometric readers: used to input biometric data • Biometric data is based on unique physiological characteristics (fingerprint, hand geometry, face, iris of the eye) or personal traits (voice, signature) • Readers can be stand-alone or built into another piece of hardware (keyboard, mouse) • Also being built into computers and storage devices to allow access only by authorized individuals • Most often used for access control and to verify transactions

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