Input/Output Devices (I/O) devices

• keyboards
• pointing devices
  • mouse-invented by Doug Englebart, Turing Award recipient. Rollers are used to sense side-side or up-down movement.
  • touch pen-used in "palm top" computers. Pressure creates contact between two layers of electrically conductive material to complete a circuit. These are used in conjunction with handwriting recognition software.
  • light pen-a light cell in the pen tip senses light from the screen
  • track ball-upside down mouse.
  • touch screen-a touch interrupts an infrared light beam
  • touch pad-an electronic grid under the pad senses your finger or thumb.
  • joystick-often used in games
  • pointing stick/trackpoint-small device used on the keyboards of laptops
• scanners-a bright light is directed across the page. Mirrors are used to reflect the image to a CCD (charge coupled device). The CCD converts the light to electrical current. The current is then converted to a digital value.
• digital camera
• voice recognition
• OCR-optical character recognition/reader
• MICR-magnetic ink character recognition/reader
• OMR-optical mark recognition/reader
• bar codes-used in POS (point of sale) systems. 3 widths of bars and spaces. A light beam is bounced off the bar code and the reflected beam is measured. The UPC (universal product code is the most common. This is used to encode a 10 digit number identifying a product number and manufacturer.
• monitors
  • CRT-cathode ray tude. 3 electron guns (red/green/blue) beams strike a phosphur coating on the back of the screen causing it to light up. Resolution is measured in pixels.
  • LCD-liquid crystal display. Liquid crystals are trapped between layers of glass. A voltage causes the crystals to become opaque. Active matrix systems offer higher resolution (a transistor controls each crystal cell). Gas plasma screens used neon gas instead of liquid crystals.
• laser printers-a laser is used to write an electrostatic charge on paper. The charge causes toner to adhere to the paper. The toner is then baked onto the paper.
• ink jet printers-A print head moves across the paper to write the image. An electric charge is used to head a small bubble of ink that expands and is forced through a small nozzle onto the paper.

1) Adaptive Technologies for the disabled
2) How will we evolve in response to technology