Input and Output Devices

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Input and Output Devices
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Input Devices

• Input devices are used to get data into a
  system. Examples of input devices are
• Keyboard
• Mouse
• Tracker Ball
• Touch sensitive pad
• Joystick
• Light pen

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Keyboard

• Types of keyboards
• QWERTY
• Concept
• Braille

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Point and Click devices

• Point and Click devices include mouse, tracker
  balls, touch sensitive pads, joysticks, light
  pens.

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Mouse

• The mouse translates movement on the desktop into
  digital information

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Tracker ball

• The tracker ball is essentially an upside down
  mouse.
• Instead of moving the mouse on the table top, the
  ball is rotated.
• This achieves the same result as using a mouse
  but takes up far less room.

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Touch Pad

• We usually find touch pad on notebook computers
• A stylus or the users finger is pressed gently
  onto the pad, and as it is moved the cursor moves
  on the screen.

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Joystick

• These are most commonly used to interact with
  computer games, although they are also used in
  other circumstances (e.g. on hospital scanners).

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Light Pen

• Light pens are usually used with specialist
  design software.
• The light pen works by being touched against the
  screen.
• As the pen is moved on the screen, the cursor
  moves

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Readers

• The most common types of reader used include
  magnetic strip readers, barcode readers, optical
  character readers/recognition, magnetic ink
  character readers/recognition, and optical mark
  readers/recognition.

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Magnetic strip readers

• The most common magnetic tape readers are those
  used at electronic points of sale (EPOS).
• These read the personal data stored on the
  magnetic strip of a credit or debit card.

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Barcode Readers

• Barcodes are used in shops, libraries, luggage
  handling, and stock control.
• The lines on a barcode represent numbers, and can
  be scanned very quickly using a laser scanner.

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Optical character readers/recognition

• Optical character recognition is a method of
  inputting text using a scanner.
• It requires special software to convert the
  scanned image of each letter into an ASCII code

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Magnetic ink character readers/recognition

• Magnetic ink characters are printed at the bottom
  of cheques.
• They are used by banks to identify the bank a
  customer banks with, the individual branch where
  their account is held, and the customers bank
  account number

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Optical mark readers/recognition

• Optical mark recognition sense marks made on
  specially designed forms (e.g. multiple choice
  answer sheets, lottery cards).
• OMR is a very cheap, easy and quick to handle
  system of inputting data, but if a user makes a
  mistake they are difficult to correct.

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Punched cards

• Punched cards and tape were used by the first
  computers to store programs and data.
• They are seldom used today except for clock
  cards, which records when a person starts and
  ends work, and Kimball tags, which are used for
  stock control.

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Sound capture devices

• The most common use of sound capture devices
  involves the use of voice recognition software
  and microphones.
• Voice recognition software remembers the way a
  user speaks, and converts their speech into text
  that appears on screen.
• Although voice recognition software has become
  increasingly sophisticated, many such programs
  have difficulty converting more than 90 of
  common words accurately.

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Terminals

• EPOS (Electronic Point Of Sale) and EFTPOS
  (Electronic Fund Transfer at Point Of Sale)
  terminals are connected, via secure Internet
  connections, to the computers of the main banks
  and credit card companies.
• EPOS and EFTPOS allow a retailer to transfer the
  cost of what they have sold to a customer from
  the customers credit card or bank account to
  their own bank account.
• This is much faster than accepting payment by
  cheque, and more secure than accepting payment in
  cash.
• It also gives the retailer an opportunity to
  collect information about their customers, and to
  develop individual customer profiles (i.e. know
  what an individual customer may want to buy).
• This helps to retailer to target individual
  customers with special offers etc.

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Digital imaging devices

• These include video digitisers, scanners, digital
  cameras, and web cams.

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Video Digitisers

• The video digitiser is a combination of hardware
  and dedicated software that converts an analogue
  signal into a digital signal.
• This is the basis of most set top boxes that give
  access to digital television on standard
  television sets.
• It can also be used to capture still images
  from video.

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Scanners

• Scanners are used to scan text or images so that
  they can be stored on and manipulated by
  computer.
• The scanner converts the text or image into a
  digital signal which it sends to the computer.
• The user can then decide whether they want to
  store or manipulate what they have scanned.

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Digital cameras

• Digital cameras convert the analogue image seen
  through the cameras lenses into a digital signal
  that can be stored.
• Each picture is split up into millions of tiny
  squares (or pixels), each of which is a different
  colour.
• Each pixel is stored as a bit of digital
  information.

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Web cams

• Web cameras are small digital cameras which are
  attached to computers so that still and motion
  digital images can be captured and used.
• They are often used in conjunction with the
  Internet so that people can videoconference.

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Output devices

• Output devices are used to get data out of a
  system.

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Visual devices

• The most common visual device is the visual
  display unit (VDU).
• These are also known as computer screens and
  monitors.
• The types of visual display unit found in common
  usage are based on cathode ray tube (CRT) or
  liquid crystal display (LCD) technology.

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CRT
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LCD

• A simple black - or - white LCD display works by
  either allowing daylight to be reflected back out
  at the viewer or preventing it from doing so - in
  which case the viewer sees a black area. The
  liquid crystal is the part of the system that
  either prevents light from passing through it or
  not. The crystal is placed between two
  polarising filters that are at right angles to
  each other and together block light. When there
  is no electric current applied to the crystal, it
  twists light by 90o, which allows the light to
  pass through the second polariser and be
  reflected back. But when the voltage is applied,
  the crystal molecules align themselves, and light
  cannot pass through the polariser the segment
  turns black.Selective application of voltage to
  electrode segments creates the digits we see.

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Printers

• The three main categories of printers are
• Laser printers
• Ink-jet printers
• Dot-matrix printers

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Laser printers

• A laser printer is a common type of computer
  printer that rapidly produces high quality text
  and graphics on plain paper. As with digital
  photocopiers, laser printers employ a xerographic
  printing process but differ from analog
  photocopiers in that the image is produced by the
  direct scanning of a laser beam across the
  printer's photoreceptor.

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Laser Printer
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Ink-jet

• Inkjet printers operate by propelling
  variably-sized droplets of liquid ink onto almost
  any sized page. They are the most common type of
  computer printer for the general consumer due to
  their low cost, high quality of output,
  capability of printing in vivid colour, and ease
  of use.

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Ink-jet
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Dot - Matrix

• A dot matrix printer or impact matrix printer
  refers to a type of computer printer with a print
  head that runs back and forth on the page and
  prints by impact, striking an ink-soaked cloth
  ribbon against the paper, much like a typewriter.
  
• Dot matrix printers, like any impact printer, can
  print on multi-part stationery or make
  carbon-copies. Impact printers have one of the
  lowest printing costs per page. As the ink is
  running out, the printout gradually fades rather
  than suddenly stopping partway through a job.
  They are able to use continuous paper rather than
  requiring individual sheets, making them useful
  for data logging. They are good, reliable
  workhorses ideal for use in situations where
  printed content is more important than quality.

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Dot matrix
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Plotter

• There are two types of main plotters. Those are
  pen plotters and electrostatic plotters.
• Plotters are used primarily in technical drawing
  and CAD applications, where they have the
  advantage of working on very large paper sizes
  while maintaining high resolution. Another use
  has been found by replacing the pen with a
  cutter, and in this form plotters can be found in
  many garment and sign shops.

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Plotters
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Computer controlled devices

• A variety of different control devices can be
  connected to a computer.
• These include robotic arms and motors (also known
  as actuators).
• The most common use of computer controlled
  devices is in computer-aided manufacturing.

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Input-Output Devices

• Touch Screen
• Modem