ICT Unit 2

  • Created by: Leila
  • Created on: 01-03-15 15:51
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  • ICT Unit 2
    • Input devices
      • Manual input devices
        • Keyboard- qwerty keyboards (each key connnected to a switch, sends signla to CPU when pressed) display keyboards (each switch has a symbol or word on it representing a piece of data)
        • Pointing devices: mouse, touchpad- like a touch sensitive mouse instead of buttons, trackerball- work in same way as a ball mouse but ball is moved by hand), joystick-can be moved in any direction, computer gets info from sensors in the joystick, graphics tablet- touch sensitive surface and stylus, touch screen and light pen.
        • Digital camera-save images as a series of dots called pixels, can be uploaded to computer and edited.
        • Scanner- converts pictures into digital data. Different parts of picture given codes, computer builds up a map of information based on these bits of data.
        • Microphone: input data into voice-recognition systems which convert sound into text or commands. Also record sound so it can be stored digitally and sent over the internet.
        • Music keyboard: enter music into a computer package.
      • Direct input methods
        • Data is entered directly without human intervention. Sometimes called direct data entry. Used when large amounts of similar data need to be entered.
        • Optical mark recognition (OMR): uses an optical mark reader to detect marks made in certain places on specially printed forms. Used in mutliple choice exams and registers.
        • Magnetic ink character recognition (MICR): uses a magnetic ink character reader to input characters that have been printed in special ink. Banks use it to process cheques.
        • Optical character recognition (OCR): uses a scanner and software to convert text and images into a document that can be edited by a word processor. Used for reading typed postcodes.
        • Bar codes: a bar code is a set of lines of different thicknesses that represent a number, which is read by a bar code reader. Most products in shops have unique printed bar codes. They work by shining a beam of light on the lines and detecting to amount of light that is reflected back.
        • Magnetic stripe readers: a magnetic stripe is a thin band of magnetic tape found on the back of a debit or credit card, identity cards and electronic key cards. The stripe stores data which can be read by the reader.
        • Chip and pin readers: credit and debit cards now made more secure by the chip on the card which is more diffcult for a hacker to read.
      • Sensors
        • Used to input data based on temperature, pressure, light levels. infrared etc. The analogue data must be converted to digital data that the computer can understand using a converter. Data logging automatically collects data over a period of time without the need for human intervention.
          • Used in weather monitoring, industrial processes and scientific experiments.
    • Output devices
      • Monitors: (CRT and TFT) display text, graphics and video. Some have internal speakers. A multimedia projector is used when giving a presentation.
      • Dot matrix printers: uses a set of pins to press and inked ribbon against the paper to leave a coloured dot on the paper. Dots can be in controlled patterns to produces required rext output on paper.
        • Printers
      • Inkjet printers: work by squirting ink at the page out of nozzles, one for each colour used, and are quiet to operate. Produce good quality text and graphics hard copy.
        • Printers
      • Laser printers: work by using a laser to draw the required outputs onto a drum. The laser etches onto the drum a negative image of the page by removing electrical charge. The toner cartridge contains ink and as the drum passes onto it the ink is attaracted to the charged areas of the drum and then trasferred onto the paper. The fuser unit heats the paper to fuse the ink.
        • Plotters: a plotter uses a pen to draw accurate line drawings and are often used in computer-aided design (CAD). Two types- flatbed and drum plotters.
        • Speakers: computers can output music, voices and sounds using speakers. Headphones are personal speakers. Buzzers are often used in control applications.
        • Control devices
          • Are used to change some physical value in response to a command from a computer
            • Examples: motors to operate machines/open windows, buzzers to sound warnings, heaters to increase temperature, lights used as signals to the user and lights as output devices to provide light in a greenhouse.


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