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    Input Output devices

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    1 : devices... Inputs and Output
    2 : Keyboard The commonest way to enter data into a computer. Each key is simply a switch, which when pressed, results in a digital code being sent to the computer.
    3 : Mouse The movement of the mouse over a flat surface is mirrored by a pointer on the monitor screen. Under the mouse is a ball which rolls and turns two shafts, one for each direction - left/right & up/down. Buttons on the mouse enable selections to be made from menus, movement of objects around the screen, and painting or drawing.
    4 : Touch sensitive screen This device acts like a mouse that the user can move by touching the screen. It is used by people who find using a mouse difficult, too time consuming or if it might get stolen / damaged.
    5 : Bar code reader The bar coded item is swiped over a laser scanner is swiped over the bar code to read in the data. It is the same as a scanner but due to the simple nature of the bar code the scanning is very rapid.
    6 : Scanner Like a photocopier it scans a full page with laser light but instead of printing copies, it transmits the image to the computer as digital code, which can be saved as a file. In effect, it performs the exact opposite function to a printer by converting a printed page into a computer file.
    7 : Speech synthesiser Output device used to help people who can’t see visual outputs from the computer. It produces a human-like voice.
    8 : Digital camera Light received through the lens is converted to digital signals by sensors, rather than stored by chemical change on a film as in a normal camera. The resulting "photograph" can then be stored on a computer and used just like any clipart files.
    9 : Other devices Magnetic strip reader - used on credit card type devices. The information is stored on the tape on the back of a card. The machine can read and write to it. Optical mark reader - similar to a bar code reader but uses infra-red light to scan pencil marks on prepared forms such as multiple-choice examination answer sheets or lottery tickets. Optical character reader - uses an ordinary scanner to take a photographic image of printed or even hand-written text. Special software then looks at the image, recognises each character and converts it into a text file
    10 : Other devices Magnetic ink character recognition - uses ink containing magnetic particles. This method is used by banks to print on a cheque the amount that it is made out for, then it is scanned into a computer. Printers - output text and image to paper. Dot matrix is old fashioned noisy, like a typewriter. Inkjet uses liquid ink that is squirted at the paper. Laser printers work like photocopiers which use powdered ink which sticks to the paper and then heated to make it stick. The process is fast and quiet. Digital camera - light received through the lens is converted to digital signals by sensors, rather than stored by chemical change on a film as in a normal camera. The resulting "photograph" can then be stored on a computer and used just like any clipart files.

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