What you'll learn
Input and output devices form a fundamental component of computer systems and feature prominently in CIE IGCSE Information and Communication Technology Paper 1 and Paper 2. You must understand how different devices work, their applications in real-world contexts, and why particular devices suit specific tasks. Exam questions regularly require you to identify appropriate devices for given scenarios and justify your choices.
Key terms and definitions
Input device — hardware that allows data and instructions to be entered into a computer system for processing.
Output device — hardware that presents processed data from a computer system to the user in a usable form.
Sensor — an input device that automatically measures physical properties such as temperature, light, or pressure and converts them into electrical signals.
Actuator — an output device used in control systems that converts electrical signals into physical movement or action.
Biometric device — an input device that recognizes unique physical characteristics such as fingerprints, iris patterns, or facial features for identification purposes.
Resolution — the number of pixels that make up an image on a screen or printed page, typically measured in dots per inch (DPI) or pixels.
Touchscreen — a dual-function device that acts as both an input device (detecting touch) and output device (displaying information).
Digitizer — a device that converts analogue information into digital format, such as a graphics tablet converting hand movements into digital coordinates.
Core concepts
Manual input devices
Keyboards remain the primary text entry device. Standard QWERTY keyboards suit office work and data entry, while specialized versions exist for specific purposes. Concept keyboards feature programmable overlays with pictures or symbols, making them ideal for restaurants (menu items), primary schools (simplified interfaces), and fast food outlets where speed and ease of use matter more than flexibility.
Mice and pointing devices control the cursor position. Traditional optical mice use LED light to detect movement on surfaces, while laser mice offer higher precision. Trackballs require less desk space as the ball rotates in a fixed housing — beneficial for CAD workstations with limited space. Touchpads dominate laptop designs due to their compact, integrated nature.
Graphics tablets allow designers and artists to draw naturally using a stylus. The tablet surface acts as a digitizer, converting pen position and pressure into coordinates. Digital artists, architects, and animators prefer these over mice for detailed work requiring variable line thickness and natural hand movements.
Automated input devices
Scanners digitize physical documents and images. Flatbed scanners suit offices needing to archive paper documents, while hand-held scanners work for inventory management in warehouses. Key specifications include optical resolution (measured in DPI) and colour depth (bits per pixel). A 600 DPI scanner provides sufficient quality for most business documents.
Barcode readers identify products through parallel lines of varying thickness. Supermarkets use laser scanners at checkpoints for rapid stock identification and automatic price lookup. Libraries employ them for book loans and returns. The scanner reads the barcode pattern, converts it to a product code, then queries a database for associated information.
QR code readers, typically smartphone cameras with dedicated apps, store more data than traditional barcodes through two-dimensional patterns. Museums use them for interactive exhibits, advertisers for direct website links, and payment systems for transaction data.
RFID (Radio Frequency Identification) readers detect tags without line-of-sight contact. Active RFID tags contain batteries and transmit signals over several metres — useful for tracking shipping containers. Passive tags draw power from the reader's signal and work over shorter ranges — employed in contactless payment cards, pet identification chips, and library book tracking.
Magnetic stripe readers extract data from cards' magnetic strips. Banks use them in ATMs and chip-and-PIN terminals, hotels for electronic room keys, and transport systems for travel cards. The reader detects magnetic field variations encoded in three tracks on the stripe.
Chip and PIN readers access data from embedded microchips, offering greater security than magnetic stripes through encrypted data storage. The customer enters a PIN to authorize transactions, reducing fraud from stolen cards.
Optical Mark Recognition (OMR) detects marks on paper forms. Schools and examination boards use OMR for multiple-choice answer sheets, market research companies for survey forms. The scanner identifies pencil marks in predetermined positions, offering rapid data capture for high-volume processing.
Optical Character Recognition (OCR) converts scanned text images into editable digital text. Companies digitizing archived documents, automated number plate recognition systems, and invoice processing all employ OCR. The software analyzes character shapes and patterns, though accuracy depends on print quality and font clarity.
Magnetic Ink Character Recognition (MICR) reads characters printed with magnetic ink. Banks print cheque details (account number, sort code, cheque number) in MICR font at the bottom of cheques. The technology offers security as magnetic ink is difficult to alter and remains readable even if overwritten.
Biometric input devices
Fingerprint scanners analyze unique ridge patterns. Smartphones use capacitive sensors for device unlocking, while offices employ them for secure building access. The scanner creates a digital template of minutiae points (ridge endings and bifurcations) for comparison.
Retina/iris scanners photograph the unique pattern of blood vessels in the retina or the coloured ring of the iris. High-security facilities, border control, and military installations use them where maximum security justifies the higher cost and slower processing compared to fingerprints.
Facial recognition cameras analyze facial geometry — distances between eyes, nose width, jaw shape. Airports implement them for passport control, smartphones for unlocking, and police for identifying suspects in crowds.
Sensors and control systems
Temperature sensors measure heat levels. Greenhouses use them to trigger heating systems when temperatures drop. Ovens employ them for temperature regulation. Freezers monitor storage conditions to prevent spoilage.
Pressure sensors detect force application. Car tyres contain sensors warning of low pressure. Industrial machinery uses them for safety cutoffs. Touch-sensitive buttons employ pressure sensors to detect finger contact.
Light sensors measure illumination levels. Street lights use photocells to activate at dusk automatically. Security systems employ infrared sensors detecting heat signatures for intruder detection. Cameras adjust exposure based on light sensor readings.
Moisture sensors detect water presence. Irrigation systems activate sprinklers when soil becomes dry. Dishwashers and washing machines adjust cycle duration based on moisture levels.
Proximity sensors detect nearby objects without contact. Cars use ultrasonic sensors for parking assistance, smartphones detect when held to the ear to disable touchscreens during calls, and automatic doors employ microwave sensors to detect approaching people.
Output devices for visual display
Monitors present visual information. Liquid Crystal Display (LCD) screens use liquid crystals that align when electrically charged, blocking or allowing backlight through. Light Emitting Diode (LED) monitors are LCD screens with LED backlighting, offering better contrast and lower power consumption. Organic LED (OLED) screens produce their own light per pixel, enabling perfect blacks and flexible displays.
Monitor specifications include screen size (diagonal measurement in inches), resolution (pixel dimensions like 1920×1080), refresh rate (Hz), and response time (milliseconds). Gamers require high refresh rates (144Hz+) and low response times (<5ms) for smooth motion.
Projectors display enlarged images. Businesses use them for presentations, schools for teaching, and cinemas for films. Digital Light Processing (DLP) projectors use millions of tiny mirrors, while LCD projectors separate light into red, green, and blue components. Key specifications include brightness (lumens), native resolution, and contrast ratio.
Output devices for physical media
Printers produce hard copy output. Inkjet printers spray tiny droplets of liquid ink through nozzles onto paper. They suit home users and small offices, producing high-quality colour photos on specialist paper. Running costs are higher than laser due to expensive ink cartridges, though purchase prices are lower.
Laser printers use the xerographic process: a laser charges specific areas of a photosensitive drum, toner powder adheres to charged areas, heat fuses toner to paper. Businesses prefer them for high-volume black-and-white printing due to faster speeds (pages per minute), lower cost per page, and sharper text. Colour laser printers exist but cost significantly more.
3D printers build physical objects layer by layer. Fused Deposition Modeling (FDM) extrudes melted thermoplastic, while Stereolithography (SLA) uses UV lasers to solidify liquid resin. Architects create building models, medical professionals produce prosthetics and anatomical models, engineers develop prototypes, and manufacturers make customized parts.
Plotters draw continuous lines using pens. Architects and engineers use them for large-format technical drawings and building plans requiring precise vector-based output. Cutting plotters in sign-making cut vinyl shapes for graphics and signage.
Output devices for sound
Speakers convert electrical signals into sound waves through electromagnets vibrating cones. Internal speakers suit basic audio needs, while external speaker systems with subwoofers provide quality audio for multimedia production and gaming.
Headphones deliver personal audio. Noise-cancelling models suit office environments requiring concentration, studio-quality headphones benefit audio engineers, and wireless Bluetooth versions offer convenience for mobile device users.
Specialized output devices
Actuators create physical movement in control systems. Motors open automatic doors and adjust robotic arms. Solenoids lock car doors centrally. Buzzers provide audio alerts in security systems. Valves control fluid flow in heating systems and irrigation.
Worked examples
Example 1: A supermarket needs to speed up checkouts and reduce queuing times. Recommend appropriate input and output devices, justifying each choice. [6 marks]
Model answer:
Input devices:
- Barcode scanner/laser scanner to read product barcodes quickly without manual entry [1]
- Each product has a unique barcode that the scanner reads, automatically looking up the price in the database, which is faster than typing codes [1]
- Chip and PIN reader for card payments to accept customer debit/credit cards securely [1]
Output devices:
- Receipt printer to provide customers with itemized proof of purchase showing what they bought and amount paid [1]
- Monitor/display screen facing the customer to show each scanned item and running total, allowing customers to verify prices as items are scanned [1]
- Monitor for the cashier to see the transaction details and control the checkout process [1]
Example 2: A factory uses a control system to monitor and regulate temperature in an industrial oven. Describe how input and output devices work together in this system. [4 marks]
Model answer:
- A temperature sensor continuously monitors the oven temperature and sends readings to the control computer/microprocessor [1]
- The computer compares the sensor reading against the required temperature setting [1]
- If the temperature is too low, the computer sends a signal to an actuator (heating element) to switch on and increase temperature [1]
- If the temperature is too high, the computer sends a signal to switch off the heating element or activate a cooling fan to reduce temperature [1]
Example 3: Compare the use of OCR and OMR for processing examination answer papers. [4 marks]
Model answer:
OMR:
- Used for multiple-choice papers where students fill in circles/boxes on answer sheets [1]
- Scanner detects the position of marks; very fast processing of thousands of papers; highly accurate for simple mark detection [1]
OCR:
- Used to convert written/printed text into editable digital format [1]
- Scans handwritten or typed answers and converts to text that can be searched or edited; slower than OMR and less accurate with unclear handwriting; useful for digitizing essay responses [1]
Common mistakes and how to avoid them
Mistake: Confusing input and output devices — students often classify speakers or actuators as input devices. Correction: Input devices send data into the computer; output devices receive data from the computer. Speakers receive audio signals from the computer, making them output devices.
Mistake: Providing vague justifications like "a scanner is good because it scans things." Correction: Explain why the device suits the specific context: "A barcode scanner suits supermarkets because it reads product codes automatically in under a second, reducing queue times compared to manual entry which takes 5-10 seconds per item."
Mistake: Stating that RFID requires line of sight or contact. Correction: RFID works without line-of-sight contact using radio waves, unlike barcodes which need direct scanning. This allows reading multiple tags simultaneously and through packaging.
Mistake: Claiming inkjet printers are always better than laser printers (or vice versa). Correction: Each suits different contexts. Inkjet printers are better for colour photos and home use due to lower initial cost. Laser printers suit high-volume office printing due to faster speeds and lower running costs per page.
Mistake: Describing sensors as measuring devices only, forgetting their role in automatic control systems. Correction: Sensors both measure physical properties AND provide continuous input to computers that trigger actuators in control systems — they enable automation without human intervention.
Mistake: Confusing biometric devices with each other or stating they all work the same way. Correction: Different biometric systems measure different physical characteristics: fingerprint scanners analyze ridge patterns, iris scanners photograph eye patterns, facial recognition measures facial geometry. Each has different accuracy levels, speeds, and security ratings.
Exam technique for Input and Output Devices
"Identify" questions (1 mark each): Name the device only — no explanation needed. Write precisely: "barcode scanner" not just "scanner," "laser printer" not just "printer."
"Describe" questions (2-3 marks): Explain how the device works or what it does. Use technical terminology and include multiple distinct points. For example, describing how MICR works: "Reads characters printed in magnetic ink [1]; commonly used on bank cheques for account details [1]; magnetic properties make it secure as difficult to alter [1]."
"Justify/Recommend" questions (4-6 marks): Name the device, explain what it does, AND relate it specifically to the scenario context. Address why it suits this particular situation better than alternatives. Structure: Device name → Function → Context-specific advantage.
Command word awareness: "State" requires brief answers; "Explain" requires reasoning; "Compare" requires discussion of both similarities and differences; "Evaluate" requires advantages and disadvantages with a conclusion.
Quick revision summary
Input devices enter data into computer systems: keyboards for text, mice for cursor control, scanners for digitizing documents, sensors for automatic measurement, biometric devices for identification. Output devices present processed information: monitors for visual display, printers for hard copy, speakers for audio, actuators for physical control. Choose devices based on context: barcode scanners suit retail for speed, 3D printers enable prototyping, RFID allows contactless tracking, laser printers suit high-volume offices. Control systems use sensors as input and actuators as output, with computers processing sensor data to trigger appropriate actuator responses automatically.