Input devices

Input devices

1. Keyboard

   • QWERTY Layout
     • alphanumeric keys
       • letters and numbers
     • punctuation keys
       • comma, period, semicolon etc.
     • special keys
       • function keys, control keys, arrow keys, Caps Lock key etc.
     • data can be typed very quickly
     • disadvantage : easy to make mistakes
   • Concept keyboard
     • Faster but limited
     • found in shops and restaurants
     • symbol/picture represent a piece of data
   • Braille
     • system of sequences of dots that can be read by touch
     • for visually impared people
     • Allows to enter text in Braille and also read text
   • Touch sensitive screen
     • used in info centers or ATM machines, smartphones
     • easy to use
     • more expensive
     • can be innacurate
     • Both: Input and Output

2. Pointing devices

   • mouse
     • ball under mouse moves - cursor moves
       • Sensors measure the movement of the ball in 2 directions and computer works out the direcion and distance the mouse has travelled
       • Ball can get dirty and stuck if not cleaned regularly
     • used to select and move around items displayed on screen
     • Easier to select items by slicking icons
     • Easier to move around than using arrow keys
   • tracker ball
     • not very accurate and quick
     • used by people with unsteady hands
     • rolls ball to control cursor movement
     • like an 'upside down' mouse - ball on top
   • touch pad
     • used instead of mouse on laptops
     • movement of fingers on touchpad mirrored by cursor on screen
     • hard to use if you are used to a mouse
     • takes up less space

3. Joystick

   • used for games
   • joystick is fixed to the base
   • allow movement of an object around a screen in any direction
   • have special buttons e.g 'fire' or 'jump'

4. Scanners

   • used to transfer 2D images into a file on a computer
     • picture scanned and converted into digital data
       • Scanner shines light onto paper document and measures amount of light reflected back.
       • can save time of retyping large amounts of text
     • files can be manipulaed and edited easily and quickly
     • large files can take up a lot of memory
   • Flat bed
     • useful for flat documents e.g page of a book
   • Hand held
     • can be moved around oddly shaped objects or long documents

5. Digital cameras

   • DPI (dots per inch) is called resolution
   • pictures stored on smart cards and can be transferred directly onto computer
     • images can be edited on computer, be used for documents/presentations etc.
     • can be sent as an attachment via email
   • Advantages: no expensive developing costs, no film needed
   • Disadvantages: more expensive than ordinary cameras; high-resolution images use lots of memory and battery power

6. Microphones

   • detects sound and inputs it into computer
     • converts it into digital format
       • can add spoken messages or music with presentations or emails
   • 1.Person speaks into microphone. 2.Speech recognition software converts what is said into text
   • people with disabilities can benefit from use of microphone
   • Disadvantages: 1) Should be no background noise 2) sound recorded using microphone is often not very good

7. Magnetic stripe reader

   • Dark stripe at the back of a plastic card contains data
     • e.g Bank card contains sort code and account number
       • data can be read by ATMs, cash registers and banks
     • Data is read when card is swiped through a magnetic stripe reader
       • Sends information to computer bank. Checks if there is sufficient amount available for transaction. If no - card payment is declined. If yes - payment goes through. Money is transferred from customer's bank account onto shop's account.
   • Advantages: 1) data is not visible to people 2) card cheap to produce 3) quick to read, coneinient to pay for goods
   • Disadvantage: 1) magnetic stripe might get damaged 2) card can be stolen

8. Graphic pads

   • like a pen and paper
     • made of a touch-sensitive membrane and a stylus
       • Translates the movement into digital signal which is sent to a computer
   • can be used by designers or illustrators to create accurate detailed drawings

9. MIDI

   • Musical Instrument Digital Inerface
     • used to edit and develop music by mixing with other sounds which are input from microphone
     • sound can be altered: speed up/ slowed down
     • Knowledge of software and music required
   • Variety of musical instruments used: guitar, keyboard, drums etc.
     • send messages via MIDI and get converted to digital data
       • can be sent back to instrument to reproduce signal

10. Barcode reader

    • Hand held device with a laser beam which can scan a barcode
      • the reflected light is transferred into digital data that is interpreted by the computer to identify the product
        • Product is found in the database and price is displayed
          • advantage: price changes only need to be made to a database not every single product
    • uses visible red light
    • Barcodes are used on product packages in a shop