HW

Hardware Output & Input Devices

Understanding output and input devices, their internal operation, and applications

Learning Objectives

By the end of this lesson, you will be able to:

  • Show understanding of the need for input and output devices
  • Identify hardware devices used for output
  • Explain the basic internal operation of laser printers, inkjet printers, and 3D printers
  • Understand how speakers convert digital sound into audible sound waves
  • Describe different touchscreen technologies (capacitive, infrared, resistive) and their applications
  • Explain how virtual reality headsets create immersive 3D environments
  • Understand how microphones convert sound into digital data
  • Identify appropriate input/output devices for different scenarios

Key Terms

Output Device

Hardware that displays or outputs data that has been processed or stored on a computer

Laser Printer

Non-impact page printer that uses dry powder ink and static electricity to produce text and images

Inkjet Printer

Non-impact line printer that produces good quality color prints by firing droplets of ink

3D Printer

Output device that generates a three-dimensional physical object from a digital file layer by layer

Touchscreen

Works as both input and output device; you view options (output) and touch your selection (input)

Virtual Reality Headset

Head-mounted device that provides virtual reality using paired images that create a 3D environment

Capacitive Touchscreen

Uses layers of glass that act like capacitors, detecting touch through changes in electric current

Resistive Touchscreen

Uses polyester and glass layers that complete a circuit when touched, sending signals to a microprocessor

DAC (Digital to Analogue Converter)

Converts digital data into electric current for output through devices like speakers

Plotter

Computer printer for printing vector graphics using pens to draw pictures on paper

Microphone

Input device that converts sound vibrations into electrical signals for digitization

Buffer

Temporary storage area in printers where data from the computer is stored before printing

Output Devices

An output device is hardware that is used to display or output data which has been processed or has been stored on a computer. Printers are common output devices used to print information on paper.

Laser Printer

A laser printer is an example of a non-impact page printer. Laser printers use dry powder ink rather than liquid ink and make use of properties of static electricity to produce text and images. Laser printers print the whole page in one go. Colour laser printers use four toner cartridges – blue, cyan, magenta and black.

Laser Printer Operation Simulation

FUSER

How it works: The laser creates an electrostatic image on the drum, toner sticks to discharged areas, and the paper picks up the toner which is then fused by heated rollers.

1
Data Preparation
Data from computer is sent to a printer driver which ensures data is in a format that the chosen printer can understand.
2
Buffer Storage
Data is sent to printer and stored in printer buffer.
3
Drum Charging
Drum is given electric charge and drum starts to revolve step by step.
4
Laser Imaging
At each step a laser beam is directed by mirror and lens assembly across width of drum. Laser is either switched off to leave charge or switched on to discharge position.
5
Toner Application
Drum is coated with charged toner which only sticks to positions where drum has been discharged.
6
Paper Transfer
Drum rolls over sheet of paper which is initially given an electric charge.
7
Fusing
Sheet of paper is discharged and then is passed through heated rollers to fuse toner particles and seal image on paper surface.
8
Reset
Drum is discharged before process starts again for next page.

Real-Life Example: School Report Printing

Imagine your school needs to print 500 report cards for students. The office uses a laser printer because:

  • It prints whole pages at once (faster than line printers)
  • The dry toner doesn't smudge like liquid ink
  • It can handle large volumes efficiently
  • Print quality remains consistent for all 500 reports

For a single high-quality photo, they might use an inkjet printer instead, but for bulk documents, laser is the best choice.

Inkjet Printer

Inkjet is a non-impact line printer. It produces good quality color prints. It is suitable if numbers of prints required are less because it prints slowly as compared to color laser printer.

Inkjet Printer Components

  • Print Head: Contains a large number of very small nozzles. Ink is fed to each nozzle from different ink cartridges.
  • Ink Cartridge: One cartridge for each colour (blue, yellow and magenta) and a black cartridge.
  • Stepper Motor: Connected to the print head by a belt to move print head across paper.
  • Paper Feed: Automatically feeds printer with pages as they are required.

Inkjet Printer Working

  1. Printer driver translates data into a suitable format for printer
  2. Printer receives data from computer and stores data in printer's buffer
  3. A sheet of paper is fed in
  4. Ink is supplied to the printhead from one or more ink cartridges
  5. Printhead moves across sheet depositing ink on to paper
  6. Paper is moved forward a fraction and printhead moves across paper again
  7. This continues until sheet has been fully printed

3D Printer

A 3D printer is an output device used to generate a three-dimensional (3D) physical object from a digital file. 3D printers produce solid objects which are built up, layer by layer using materials such as powdered resin, powdered metal, paper or ceramic powder using technology known as BINDER 3D PRINTING.

3D Printer Operation Simulation

How it works: 3D printers use additive manufacturing - building objects layer by layer from digital designs.

Working of 3D Printer

  1. 3D design created using computer aided design (CAD) package is split into layers
  2. Data for first layer is transmitted to 3D printer
  3. 3D printer uses a nozzle to spray material on to printer bed to create a physical layer to match design
  4. This process is repeated for successive layers
  5. When whole object has been formed it has to be cured in some way to ensure that layers are welded together

Manufacturing Techniques

Additive Manufacturing:

3D printers use ADDITIVE manufacturing in which object is built up layer by layer.

Subtractive Manufacturing:

Removal of material to make the object. It involves carving the statue out of solid stone by removing the stone not required until final item was produced.

Plotter

A plotter is a computer printer for printing vector graphics. Plotter gives hard copy of output. It draws pictures on a paper using a pen. Plotters are used to print designs of ships and machines, plans for buildings and so on.

How Plotters Work

Graphics plotter uses pens to write on a large sheet of paper constrained by sprockets along one pair of sides.

  • Sprockets can move paper forwards or backwards
  • Pens can either be parked or in use at any given time
  • Controlling circuitry and software can create drawing directly from original vector graphic file

Types of Plotters

1. Pen Plotter:

Pen plotters are used to draw or type of text. These are used in architecture or engineering to create designs.

2. Cutting Plotter:

Come with a sharp blade instead of a pen-like instrument and are used for cutting paper, mylar or vinyl.

Speaker

A speaker is an output device used to output digital sound. Digitised sound stored in a computer can be converted into sound.

Speaker Operation Simulation

How it works: Digital data → DAC → Electric current → Coil moves in magnetic field → Diaphragm vibrates → Sound waves created.

1
Digital to Analogue Conversion
Digital data is first passed through a digital to analogue converter (DAC) where it is converted into an electric current.
2
Current Flow
Current flows through coil suspended within magnetic field provided by a permanent magnet in the speaker.
3
Coil Movement
Direction of current keeps reversing, coil moves backwards and forwards.
4
Sound Creation
This movement controls movement of a diaphragm which causes sound to be created. Amount of movement will determine frequency and amplitude of sound wave produced.

Activity 1: Printer Selection

For each scenario below, choose whether a laser printer or inkjet printer would be more suitable, and explain why:

  1. A photography studio needs to print a single high-quality portrait for a client.
  2. A university department needs to print 500 copies of a 20-page course handbook.
  3. A small business needs to print color brochures occasionally (about 50 per month).
  4. A library needs to print thousands of black-and-white overdue notices each week.
Solution:
  1. Inkjet Printer: Better for single high-quality photos due to superior color reproduction and photo quality.
  2. Laser Printer: More efficient for large volumes (500 copies) and faster for multi-page documents.
  3. Inkjet Printer: Suitable for occasional color printing in small quantities; more cost-effective for low volume.
  4. Laser Printer: Ideal for high-volume black-and-white printing; faster and more economical for thousands of documents.

Check Your Understanding: Output Devices

Answer
  • [1 mark] Impact printers physically strike an inked ribbon against paper (e.g., dot matrix)
  • [1 mark] Non-impact printers do not physically contact the paper (e.g., laser, inkjet)
  • [Additional] Non-impact printers are generally quieter and produce higher quality output
Answer
  • [1 mark] The drum is given an electric charge initially
  • [1 mark] Laser discharges specific areas on the drum to create an electrostatic image
  • [1 mark] Charged toner particles only stick to discharged areas of the drum
  • [Additional] Paper is also charged to attract toner from the drum
Answer
  • [1 mark] Building objects layer by layer from digital designs
  • [1 mark] Adding material to create the final object (opposite of subtractive manufacturing)
  • [Additional] Uses materials like powdered resin, metal, or ceramic powder
Answer
  • [1 mark] Plotters use pens to draw on paper rather than spraying ink
  • [1 mark] Designed for vector graphics (lines and shapes) rather than raster images
  • [1 mark] Used for technical drawings, architectural plans, and engineering designs
  • [Additional] Paper is moved by sprockets while pens move in X-Y coordinates
Answer
  • [1 mark] DAC (Digital to Analogue Converter) converts digital data into an electric current
  • [1 mark] This conversion is necessary because speakers require analogue signals to produce sound
  • [Additional] Without DAC, digital sound files cannot be converted to audible sound waves
Answer
  • [1 mark] They process and print an entire page at once
  • [1 mark] Unlike line printers that print line by line or character printers that print character by character
  • [Additional] The drum creates a complete electrostatic image of the page before transferring to paper

Screens & Touchscreens

Screens are used to show output from computer. Modern screens use an LCD, backlit with LEDs or newer organic light emitting diode (OLED) technology. Touch screens work as both an input and an output device.

Screen Technology

OLED Technology

OLED (Organic Light Emitting Diode) uses organic materials to create flexible semiconductors.

  • Organic films are sandwiched between two charged electrodes
  • When electric field is applied to electrodes, they give off light
  • No form of back lighting is required
  • Allows for very thin screens
  • No longer a need to use LCD technology

Screen Resolution

Screen displays are based on pixels where each screen pixel is made up of three sub-pixels:

  • Red, green, and blue sub-pixels
  • By varying intensity of three sub-pixels, it is possible to generate millions of colours
  • Greater number of pixels on a screen, greater is screen resolution
Real Example:

A 4K screen has approximately 8.3 million pixels (3840 × 2160), providing much sharper images than HD (2 million pixels).

Touchscreen Technologies

A touch screen works as both an input and an output device. You view options available to you on screen (output) and you then use your finger to touch option that you have chosen (input).

Touchscreen Technology Simulation

Try it: Touch the grid cells to simulate how different touchscreen technologies detect input. Each technology uses different methods to determine touch coordinates.

1. Capacitive Touchscreen

How it Works

It is made up of many layers of glass that act like capacitors, creating an electric field between glass plates in layers.

  • When top layer of glass is touched, electric current changes
  • Coordinate where screen is touched is determined by microprocessors
Pros and Cons
Merits Demerits
Screen visibility is good even in strong light Allow only the use of bare fingers as form of inputs
This is medium cost technology
The screen is very durable (long lasting)

2. Infrared Touchscreen

Types
a) Heat Sensitive Touch Screen:

Uses glass as screen material and needs a warm object (e.g. fingers) to carry out an input operation.

b) Optical Touch Screen:

Uses glass as screen material. An array of sensors (grid form) is used to find point of contact based on which grid coordinate is touched.

Pros and Cons
Advantage Disadvantage
It allows multi touch capabilities It is relatively expensive technology
The screen is very durable (long lasting) It allows only bare fingers to be used for input (gloved fingers don't work)

3. Resistive Touchscreen

How it Works

It makes use of an upper layer of polyester (form of plastic) and a bottom layer of glass.

  • When top layer is touched, top layer and bottom layer complete circuit
  • Signals are then sent out which are interpreted by microprocessor
  • Microprocessor determines coordinate of where screen was touched
Pros and Cons
Advantage Disadvantage
It is relatively inexpensive technology Screen visibility is poor in strong sunlight
It is possible to use gloved or bare fingers It doesn't allow multi-touch capability
Screen is not durable

Activity 2: Touchscreen Technology Selection

For each scenario below, recommend the most suitable touchscreen technology (capacitive, infrared, or resistive) and explain your choice:

  1. A smartphone that needs to support multi-touch gestures like pinch-to-zoom.
  2. An ATM machine that needs to work reliably in outdoor sunlight.
  3. A factory control panel where operators might be wearing gloves.
  4. A museum interactive display that needs to detect when visitors touch specific areas.
Solution:
  1. Capacitive: Supports multi-touch gestures and provides good screen visibility. Most smartphones use capacitive technology.
  2. Capacitive or Infrared: Both have good visibility in sunlight. Capacitive is common in ATMs due to durability.
  3. Resistive: Works with gloved fingers, which is essential in factory environments.
  4. Infrared: Can detect touch without physical pressure, good for public displays where durability is important.

Check Your Understanding: Screens & Touchscreens

Answer
  • [1 mark] OLED uses organic materials that emit light when electric current is applied
  • [1 mark] OLED does not require backlighting (self-emitting), while LCD requires a backlight
  • [1 mark] OLED allows for thinner, more flexible screens and better contrast ratios
  • [Additional] OLED pixels can be turned off completely for true blacks
Answer
  • [1 mark] Capacitive screens detect touch through changes in electric field caused by conductive objects (like human skin)
  • [1 mark] Most glove materials are not conductive and therefore don't disrupt the electric field
  • [Additional] Special conductive gloves are needed for use with capacitive screens
Answer
  • [1 mark] They have two layers: upper polyester layer and lower glass layer
  • [1 mark] When pressed, the two layers make contact and complete a circuit
  • [1 mark] The microprocessor calculates the coordinates based on where the circuit is completed
  • [Additional] They work with any object that applies pressure, including gloved fingers or stylus
Answer
  • [1 mark] Screen resolution refers to the number of pixels displayed on the screen
  • [1 mark] It is measured as width × height in pixels (e.g., 1920 × 1080 for Full HD)
  • [Additional] Higher resolution means more pixels and sharper, more detailed images
Answer
  • [1 mark] Very durable and long-lasting, which is important for high-traffic public use
  • [1 mark] Good visibility in various lighting conditions, including bright sunlight
  • [Additional] Can support multi-touch capabilities for interactive displays
Answer
  • [1 mark] Each pixel is made up of three sub-pixels: red, green, and blue (RGB)
  • [1 mark] By varying the intensity of each sub-pixel, millions of different colors can be created
  • [Additional] This is known as additive color mixing - combining red, green, and blue light

Input Devices & Specialized Hardware

Virtual Reality Headset

What is VR?

A virtual reality headset is a head-mounted device that provides virtual reality for the wearer.

  • Images can be created using a 3D graphics package
  • These are fed paired images from controlling system
  • When looked at together, give eyes sensation of being in a 3D environment
  • Virtual reality is a computer-generated simulation in which a person can interact within an artificial 3-D environment

How VR Works

  • Wearer of headset can control which part of 3D environment is in view
  • They do this by moving their head or by using a controlling device
  • These are widely used with video games
  • Also used in other applications, including simulators and trainers
Real Example:

Flight simulators for pilot training use VR headsets to create realistic cockpit environments without the cost of real aircraft.

Microphones

A microphone is an input device that allows sound to be entered into a computer system. Microphones are either built into computer or are external devices connected through USB port or through wireless connectivity.

1
Sound Detection
When sound is created, it causes air to vibrate. When a diaphragm in microphone picks up air vibrations, diaphragm also begins to vibrate.
2
Coil Movement
Copper coil is wrapped around a permanent magnet and coil is connected to diaphragm using a cone. Movement of diaphragm causes a coil to move.
3
Current Generation
Coil moves backwards and forwards past the magnet. Movement of coil creates a current (electromagnetic effect).
4
Digitization
Electric current is digitized by sound card using ADC (Analogue to Digital Converter) and sends to computer.

Input of Graphic

Webcam

Device used to stream video images into a computer system

Digital Camera

Can be connected to a computer and stored images or videos can then be downloaded into computer

Scanner

Takes an image and creates a digital representation from it

How Scanners Work

A sheet of paper containing image (which may be text) is held in fixed position and light source moves from one end of sheet to other. It covers width of paper.

  • Reflected light is directed by a system of mirrors and lenses on to a Charge-Coupled Device (CCD)
  • CCD converts light into electrical signals
  • Signals are then converted into digital data

Activity 3: Device Selection

Name the most suitable input or output device for each of the following uses. Give a different device in each case:

Description of use Input or output device
Input of credit card number into an online form
Selection of an option at an airport information kiosk
Output of a single high quality photograph
Output of several hundred high quality leaflets
Input of a hard copy image into a computer
Solution:
Description of use Input or output device
Input of credit card number into an online form Keyboard/keypad/numberpad
Selection of an option at an airport information kiosk Touch screen
Output of a single high quality photograph Ink jet printer
Output of several hundred high quality leaflets Laser printer
Input of a hard copy image into a computer Scanner

Explanation: Each device is chosen based on its specific strengths - keyboards for precise data entry, touchscreens for public interfaces, inkjet for single high-quality prints, laser for bulk printing, and scanners for digitizing physical images.

Check Your Understanding: Input Devices

Answer
  • [1 mark] Uses paired images created by 3D graphics software
  • [1 mark] Each eye sees a slightly different image (stereoscopic vision)
  • [1 mark] Brain combines these two images to create depth perception and 3D effect
  • [Additional] Head tracking allows the view to change as the user moves their head
Answer
  • [1 mark] ADC (Analogue to Digital Converter) converts the analogue electrical signal from the microphone into digital data
  • [1 mark] This conversion is necessary for the computer to process and store the sound digitally
  • [Additional] Located in the sound card, it samples the analogue signal at regular intervals
Answer
  • [1 mark] Light source moves across the document, illuminating it
  • [1 mark] Reflected light is directed through mirrors and lenses onto a CCD (Charge-Coupled Device)
  • [1 mark] CCD converts light intensity into electrical signals which are then digitized
  • [Additional] The scanner builds a digital image line by line as it moves across the document
Answer
  • [1 mark] Training simulators (e.g., flight simulators for pilots, surgical simulators for doctors)
  • [1 mark] Architectural visualization and virtual tours of buildings before construction
  • [Additional] Therapy for phobias, PTSD treatment, virtual tourism, and educational experiences
Answer
  • [1 mark] Webcams are designed for continuous streaming of video in real-time
  • [1 mark] They are typically always connected and ready to use, unlike digital cameras which need to be connected each time
  • [Additional] Webcams often have built-in microphones and are optimized for low-light conditions common in indoor use
Answer
  • [1 mark] When a coil moves within a magnetic field, it generates an electric current
  • [1 mark] In microphones, sound vibrations move the coil, creating a corresponding electrical signal
  • [Additional] This principle allows mechanical sound energy to be converted into electrical energy

Key Takeaways

  • Output devices display or output processed data from a computer, including printers, screens, and speakers
  • Laser printers use static electricity and dry toner to produce high-quality prints quickly, making them ideal for large volumes
  • Inkjet printers spray liquid ink through nozzles, producing excellent color quality but at slower speeds than laser printers
  • 3D printers use additive manufacturing to build objects layer by layer from digital designs
  • Plotters use pens to draw vector graphics, making them ideal for technical drawings and architectural plans
  • Speakers convert digital sound to analogue using DAC, then use electromagnetic principles to create sound waves
  • Touchscreens act as both input and output devices, with capacitive, resistive, and infrared being the main technologies
  • Capacitive touchscreens detect conductive objects (like fingers) through changes in electric field
  • Resistive touchscreens work by pressure completing a circuit between two layers
  • VR headsets create immersive 3D environments using paired images and head tracking
  • Microphones convert sound vibrations into electrical signals using electromagnetic induction
  • Scanners digitize physical images using light sensors (CCD) to capture reflected light
  • Device selection depends on the specific task - different devices are optimized for different purposes

Question Bank

Marking Scheme & Answer
  1. [1 mark] Data sent to printer driver for formatting
  2. [1 mark] Data stored in printer buffer
  3. [1 mark] Drum charged with static electricity and rotated
  4. [1 mark] Laser beam creates electrostatic image by discharging specific areas
  5. [1 mark] Toner (dry powder) sticks to discharged areas on drum
  6. [1 mark] Toner transferred to paper and fused by heated rollers
  7. [Additional] Process repeats for each page, drum is cleaned between pages
Marking Scheme & Answer
Inkjet Printer:
  • Uses liquid ink cartridges
  • Sprays ink through nozzles
  • Better for single, high-quality color prints
  • Slower printing speed
  • Lower initial cost
  • Prints line by line
Laser Printer:
  • Uses dry powder toner
  • Uses static electricity and heat
  • Better for high-volume black & white
  • Faster printing speed
  • Higher initial cost
  • Prints page by page
Commonality: Both are non-impact printers that produce digital output on paper.
Marking Scheme & Answer
  • [1 mark] As an output device: displays information, options, and interface elements visually
  • [1 mark] As an input device: detects and registers user touch interactions
  • [1 mark] Combines display technology with touch sensing technology in one unit
  • [1 mark] User sees output (what to select) and provides input (touching the selection)
  • [Additional] Examples: smartphones, ATMs, information kiosks, tablet computers
Marking Scheme & Answer
Capacitive:
  • Uses glass layers as capacitors
  • Detects conductive objects (fingers)
  • Good visibility in sunlight
  • Supports multi-touch
  • Medium cost
  • Durable
Resistive:
  • Uses polyester and glass layers
  • Works with any object (pressure)
  • Poor sunlight visibility
  • No multi-touch
  • Low cost
  • Less durable
Infrared:
  • Uses sensors in grid pattern
  • Detects interruption of IR beams
  • Good visibility
  • Supports multi-touch
  • High cost
  • Very durable
Marking Scheme & Answer
  • [1 mark] Builds objects layer by layer from digital 3D models
  • [1 mark] Adds material gradually to create the final object (opposite of subtractive manufacturing)
  • [1 mark] Uses materials like powdered resin, metal, or ceramic powder
  • [1 mark] Each layer is printed sequentially until the complete object is formed
  • [Additional] Allows creation of complex geometries that would be difficult with traditional methods
Marking Scheme & Answer
  1. [1 mark] Sound waves cause air vibrations that move the microphone diaphragm
  2. [1 mark] Diaphragm movement causes attached coil to move within magnetic field
  3. [1 mark] Coil movement generates electric current through electromagnetic induction
  4. [1 mark] Electric current is an analogue representation of the sound wave
  5. [1 mark] ADC converts analogue signal to digital data for computer processing
Marking Scheme & Answer
  • [1 mark] Plotters are designed for printing vector graphics (lines, shapes, technical drawings)
  • [1 mark] They use pens to draw on paper rather than spraying ink
  • [1 mark] Used for architectural plans, engineering designs, ship designs
  • [1 mark] Paper moves on sprockets while pens move in X-Y coordinates to create drawings
  • [Additional] Slower than regular printers but more precise for line drawings
Marking Scheme & Answer
  • [1 mark] OLED pixels emit their own light when electric current is applied
  • [1 mark] LCD requires separate backlighting behind the liquid crystal layer
  • [1 mark] OLED allows for thinner, flexible screens and better energy efficiency
  • [1 mark] OLED provides better contrast and true blacks (pixels can turn off completely)
  • [Additional] OLED uses organic compounds that glow when electrically charged
Marking Scheme & Answer
  • [1 mark] Temporary storage area in the printer that holds data received from the computer
  • [1 mark] Allows printer to receive data faster than it can print, freeing the computer for other tasks
  • [Additional] Enables print spooling - multiple documents can be queued for printing
Marking Scheme & Answer
a) Inputting architectural drawings:

Scanner or digital camera - Can digitize large paper drawings for use in CAD software. Scanner provides higher accuracy for technical drawings.

b) Creating prototypes for product design:

3D printer - Allows rapid prototyping by creating physical models from digital designs layer by layer. Enables testing and refinement before mass production.

c) Public information system in airport:

Touchscreen kiosk - Combines output (displaying flight information) with input (allowing user interaction). Durable and intuitive for public use. Capacitive or infrared for durability.