Input, output, storage

• Peripheral Devices


  Any device that is connected and under the control of the processor, made up of mainly input, output and storage devices
• Input Device


  Any device that allows data to be fed to the computer
• Types of Scanners


  • 2D Scanners
  • 3D Scanners
• 2D Scanners


  • Used to input data from paper documents (hard-copy) directly into the computer
  • The document is scanned as an image and stored
  • Can come with OCR (Optical Character Recognition) software to convert text or handwriting into computer readable form
  • Scanned information can be stored in PDF format
• JPEG


  A format for storing scanned images
• How 2D Scanners Work

  1. A bright white light from a xenon lamp is passed onto the image

  2. A scan head is passed over the document from top to bottom

  3. The image is scanned and sent to a lens through a series of mirrors

  4. The lens focuses the image onto a CCD (Charge Coupled Device)

  5. The CCD converts the image into a digital format, normally stored as a JPEG file
• Uses of 2D Scanners with OCR


  • Processing utility bills
  • Scanning passport text data like passport number, name
  • Scanning photo of person to be compared with photo on passport using face recognition software
• Barcode


  A series of dark and light parallel lines of varying thickness, representing numbers 0-9 in a unique series of lines
• Barcode Structure


  • Different coding schemes for digits on left and right hand sides
  • Left hand digits start with light line and have odd number of dark lines, right hand digits start with dark line and have even number of dark lines
  • Barcode read by red laser/LED, dark lines not reflected and converted to bit 1, light lines reflected and converted to bit 0
• QR Code


  A 2D barcode that can store around 7000 characters, read by camera in mobile phone
• Uses of QR Codes


  • Delivering URL of online shopping website addresses
  • Delivering other information
• 3D Scanners


  • Scan solid objects and create a 3D digital model
  • Project a line of laser light onto the surface and use sensors to detect the changing distance and shape of the laser line
• Uses of 3D Scanners

  • Used in CAD (Computer Aided Design)
• Digital Cameras


  • Controlled by a microprocessor and equipped with memory
  • The photo is captured as light enters through the lens and hits the CCD (Charge Coupled Device) sensor
  • The CCD converts the light into a digital image
• Digital Camera Features


  • Auto flash
  • Automatic shutter speed control
  • Automatic aperture size control
  • Red-eye removal
• Interactive Whiteboards


  • Display images using a digital projector
  • Allow user to write on the whiteboard using a special pen or finger
  • Text, handwriting or drawings are stored in electronic form
  • Come with special software for controlling the board, drawing facilities, and subject-specific facilities
• Keyboard


  Can be used to type documents, use keystroke shortcuts, access menus, play games, and perform a variety of other functions
• 1. 1 operture open
• In the aperture is open too much, the picture may become blurred due to overexpos
• Apperture open
• OUTPUT DEVICES


  INTERACTIVE WHITEBOARDS
• Images are displayed uning a digital projector

  1. Allow a user to write on the whiteboard (using social pen or finger)

  2. Text, handwriting or drawings are stored in an electronic form

  3. Comes with a special software which allows Controlling the board (driver)

  4. Special drawing facilities

  5. Subject specific facilities (Maths/Chemistry)
• Interactive whiteboards


  Can be used as a large touch screen for other standard software
• The electronic board itself is just an input device
• Keyboard Basics


  Using a keyboard, a person can type a document, use keystroke shortcuts, access menus, play games and perform a variety of other tasks
• Keys on a keyboard

  • typing keys
  • A numeric keypad
  • Function keys
  • Control keys
• Typing keys


  Include the letters of the alphabet, generally laid out in the same pattern used for typewriters
• Numeric keypad


  For the business environments needed for speedy data entry. It consists of a set of 17 keys, arranged in the same configuration found on adding machines and calculators
• Example of control keys

  • Home
  • End
  • Insert
  • Page Down
  • Escape
• Keyboard circuitry


  A keyboard has an internal circuitry that carries information to and from the processor. A large part of this circuitry makes up the key matrix
• Key matrix


  A grid of circuits underneath the keys. In all keyboards (except for capacitive modell, each circuit is broken at a point below each key. When you press a key, it presses a switch, completing the circuit and allowing a tiny amount of current to flow through
• How a keyboard works

  1. When the processor finds a circuit that is closed, it compares the location of that circuit on the key matrix to the character map in its read-only memory (ROM)

  2. A character map is basically a comparison chart er lookup table. it tells the processor the position of each key in the matrix and what each keystroke or combination of keystrokes represents

  3. The computer can also use separate character maps, overriding the one found in the keyboard. This can be useful if a person is typing in a language that uses letters that don't have English equivalents on a keyboard with English letters
• Optical mouse


  Internal components: LED, CMOS sensor, microprocessor
• How an optical mouse works

  1. A LED shines light onto a surface through a ring at the base

  2. The light is reflected off the surface through the ring

  3. The CMOS sensor detects the reflected light and capture images of the surface (1500 per s)

  4. The images are sent to the microprocessor

  5. As the mouse moves, the sensor detects irregularities on the surface

  6. The microprocessor translates those irregularities into X and Y direction movements of the pointer on the screen
• Trackball mouse


  Internal components: socket, sensors, ball
• How a trackball mouse works

  1. It is like an upside down mouse

  2. It has a ball supported by a socket that contains sensors that can detect rotation about the X and Y axis

  3. When the ball is rolled, the data from the sensor is processed by the microprocessor

  4. The processed information is then translated into movements of the pointer on the screen
• Microphone


  Internal components: diaphragm, coil, magnet, dust cap
• How a microphone works

  1. Sound vibration hits the diaphragm

  2. The movement of the diaphragm causes a coil to move

  3. The movement of the coil induces a current due to electromagnetic effect

  4. The electric current is digitised

  5. The digital content is played back using software
• Touchscreens


  There are three types: Capacitive, Resistive, Infra-red
• Touchscreens


  • They are used as input device which allow starting of applications by a simple touch
  • They can also be used to perform similar functions as a pointing device
  • They are mostly used in portable devices like mobile phone, tablet PC etc