input / output devices

• Input device

  Any device that allows you to pass information from the outside world into a computer system
• Input devices specified by the exam board

  • Barcode scanners
  • Digital cameras
  • Keyboards
  • Microphones
  • Optical mouse
  • QR scanners
  • Touch screens
  • 2D and 3D scanners
• Barcode scanner

  • Shines a red laser at a barcode to illuminate it, the white lines reflect the light back while the black lines absorb some of the light and reflect less, the strength of the reflection from each line is interpreted by a microprocessor and converted into a binary value
  • Used for scanning goods at supermarket checkouts, checking library books in and out, and tracking packages
• Digital camera

  • Light enters the camera and falls onto a sensor made up of millions of pixels, each pixel measures the light intensity and a microprocessor converts these values into digital data representing color values
  • Integrated into smartphones, used by professional photographers, and in security/surveillance systems
  • Allow for instant photographs, images and movies, no development time required, photos can be easily transmitted and edited
• Keyboard

  • Each character on the keyboard has a corresponding character value, the key presses are converted into a digital signal which the computer interprets
  • Connected to most desktop computers via USB, wireless or Bluetooth, built into laptops and used in tablets/smartphones
• Optical mouse

  • Uses a red LED and a sensor to determine the movement of the mouse relative to the surface, a microprocessor analyzes the speed and distance of the movement and replicates this on screen via a virtual cursor
  • Used for navigation and interaction with graphical user interfaces, no moving parts so more reliable
• Microphone

  • Vibrations caused by sound waves cause a coil to move around a magnet resulting in electromagnetic field changes, these changes are converted by a microprocessor and an analog to digital converter into a digital representation of the sound
  • Used for making music recordings, dictation, in radio/TV/films, telephone calls, security and video-based online communication
• QR code scanner

  • QR codes are read using a camera, typically on a mobile device, an app then processes the image converting the squares into readable data
  • Used for advertising, providing quick links to websites, sharing contact details, accessing electronic travel passes and event tickets, can encode much more information than traditional barcodes
• Types of touch screen technology

  • Resistive
  • Infrared
  • Capacitive
• Resistive touch screen

  • Consists of two conductive layers with the top layer being flexible, the two layers are separated by an insulating layer, when the upper layer is pressed the two layers connect completing a circuit
  • Cheap to produce, can be activated by any object, resistant to surface contaminants, but lower image clarity and precision
• Capacitive touch screen

  • Composed of a protective layer, a transparent conductive layer, and a glass substrate, touching the screen with a bare finger or stylus changes the electrostatic field of the conductive layer
  • Provide excellent image clarity and high precision, allow for multiple touches, but require a bare finger or capacitive stylus for activation
• Infrared touch screen

  • LEDs shine an infrared matrix across the screen, when the screen is touched the beams are interrupted and the point of interruption determines the touch position
  • Provide excellent image quality, have an unlimited touch life, and can physically scale in size, but are sensitive to interference from ambient light, water, and snow
• 2D scanner


  • Shines a bright light across a document to measure the levels of reflected light and create a digital version of it
  • Used for creating digital versions of documents and photographs, can also be used for reading passports at airport security
• 3D scanner

  • Shines a laser light over the surface of an object to record its geometry and dimensions and create a digital model
  • Used to create 3D models for computer-aided design software or 3D printing, used in dentistry, product development, quality inspection, and research
• Output device

  Any device that can take data stored in a digital form and convert it into another form humans can process such as sound, images or vibration feedback
• Common output devices

  • Actuators
  • Digital Light Processing (DLP) projectors
  • Inkjet printers
  • Laser printers
  • Light Emitting Diode (LED) screens
  • Liquid Crystal Display (LCD) projectors
  • Speakers
  • 3D printers
• Actuators

  • Come in a variety of shapes and sizes, each version purpose-built for a specific function, but they essentially all achieve the same goal which is to carry out some sort of physical movement
  • Can be used for starting and stopping a pump or flow control device, opening and closing an automatic door, turning a wheel, opening and closing a valve, starting and stopping conveyor belts, operating an aircraft's wing flaps, and much more
  • Commonly used in conjunction with a motor to translate digital signals into actual real-world movement of physical objects
  • Also used with sensors to control many kinds of mechanisms
• Digital Light Processing (DLP) projectors

  • Use millions of micro mirrors arranged in a matrix grid and placed onto the surface of a small microchip within the projector itself
  • White light is Shone through a rotating color filter to produce the image
  • An angled mirror changes the color intensity for projecting a computer output onto a wall, a whiteboard or projection screen
  • Often used for personal home and professional settings
  • Provide higher contrast ratio, smoother video, are generally smaller and lighter, and thus more portable, and better suited to dusty or smoky atmospheres and environments compared to LCD projectors
• Liquid Crystal Display (LCD) projectors

  • Use three mirror filters to separate an image into its red, green and blue wavelengths
  • These images are then passed through a prism and recombined
  • The full color image is then passed through a lens and projected
  • Often used for projecting a computer output onto a wall, whiteboard or projection screen
  • Provide a sharper image, better color reproduction, are typically less expensive, and quieter in operation compared to DLP projectors
  • Have lower power usage and thus produce less heat
• Inkjet printers

  • Force tiny droplets of liquid ink through very fine nozzles onto a sheet of paper to replicate a digital document or image
  • Most commonly used for small scale print jobs
  • Cheaper and smaller, so very popular for personal and home use
  • Excellent for printing out high quality photos, especially when used with specialist photo paper
• Reason for inkjet and laser printers

  There is still a need to produce physical copies of information stored in electronic format. Printouts or hard copies can be easily transported and viewed at any time without the need for an electronic device or an active internet connection.
• Laser printers

  • Use toner cartridges containing powdered electrostatically charged ink
  • A laser draws a mirror image of the printer page onto a drum, creating negatively charged areas
  • The drum then picks up the positively charged ink particles and bonds them with a sheet of paper using heat
  • Produce high quality but inexpensive printing
  • Very fast and accurate for non-color documents and images
  • Have a lower running cost per page compared to an inkjet printer
  • Often found in non-personal areas like schools and offices
• Liquid Crystal Display (LCD) screens

  • Made up of millions of tiny liquid crystals that form a matrix of pixels which can be affected by changes in applied electric fields
  • Require some form of backlighting, often produced by a fluorescent lamp or LED
  • Used for TVs, monitors, laptops and mobile phones
  • Gradually being phased out in favor of newer technologies such as LED and OLED
• Light Emitting Diode (LED) screens


  • Use tiny light emitting diodes to produce a bright image almost instantly without the need for any additional backlighting
  • Replacing LCD displays in more and more situations including typical home use, monitors, laptops and mobile devices
  • Easy for multiple LED screens to be joined together, making them ideal for very large displays used at concerts, festivals and sporting events
  • Generally considered better than LCD because they offer better image quality and viewing angles, have a longer life span, and require no additional backlighting so can be thinner and lighter
• Speakers

  • The counterpart to a microphone, an input device, that works in the opposite way
  • A digital representation of a sound is passed through a digital to analog converter (DAC) which can be further boosted by an amplifier before being passed to a speaker to create analog sound waves
  • Used in a wide variety of situations including TV, films, video games, live music, music recording playback, alarm systems, and more
  • Provide a way to take digital sounds or recordings and output them in a form that can be heard by the human ear
• 3D printers

  • Based on a combination of inkjet and laser printer technology
  • Work by depositing layers of material, often plastic, on top of each other to slowly build up a 3D object
  • Can also use powdered resin, metal, paper, ceramic, concrete and even certain types of foods
  • Used to make inexpensive custom-made prosthetics, spare parts, rapid prototypes of objects, and a wide range of personalized items such as keyrings
  • Allow the production of real world models of virtual objects created using computer design software, including objects with intricate internal spaces and even moving parts
  • Provide a means of manufacturing with minimum waste
• The exam board has greatly simplified the syllabus for exams taking place from 2023 onwards. Candidates no longer need to know details of how each output device actually operates, only what each device does, why it does it, and when it might be used.
• A gaming controller can be considered a primarily input device, even though it may also have output capabilities like speakers and vibration feedback.
• A cash point machine would likely use a combination of input devices (card reader, keypad, security camera) and output devices (monitor, printer, speaker) as part of its system.