4.2e Input and output devices — Edexcel 4CP0

Input Devices

An input device sends data from the outside world into the computer system for processing.

Common input devices and their uses

Device	How it works	Typical use
Keyboard	Key presses converted to character codes	Typing text, commands
Mouse	Movement detected by optical sensor	Selecting, clicking, dragging
Touchscreen	Detects finger contact (capacitive or resistive)	Smartphones, tablets, kiosks
Microphone	Sound waves → electrical signals → digital	Voice input, recording audio
Camera/webcam	Lens focuses light onto sensor (CCD/CMOS)	Video calls, photographs
Barcode scanner	Laser reads reflected light from barcode lines	Shops, warehouses, libraries
QR code reader	Camera decodes 2D matrix pattern	Payments, tickets, links
Magnetic stripe reader	Reads magnetised particles on card	Credit/debit card transactions
Biometric scanner	Reads fingerprint, iris, face geometry	Security, device unlock
RFID reader	Radio waves power and read RFID tag	Contactless payments, access control
Graphics tablet	Stylus position detected electromagnetically	Graphic design, illustration

Output Devices

An output device takes processed data from the computer and presents it to the user or acts on the physical world.

Common output devices and their uses

Device	How it works	Typical use
Monitor/screen	Pixels emit light (LCD, OLED, LED)	Displaying visuals, text, video
Printer (inkjet)	Sprays ink droplets onto paper	Colour documents, photos
Printer (laser)	Laser charges drum, toner fused to paper	High-volume, fast text printing
3D printer	Deposits material layer by layer	Prototyping, manufacturing
Speakers	Digital → analogue signal → vibrate cone	Audio output, music, alerts
Headphones	Same as speakers, smaller drivers	Personal audio
Projector	Light through LCD/DLP chip onto surface	Presentations, cinema
Actuator	Converts electrical signal into physical movement	Robotics, control systems

Devices that are Both Input and Output

Some devices act as both input and output:

Touchscreen — inputs touch, outputs display
Headset with microphone — inputs voice, outputs sound
Network card (NIC) — sends and receives data over a network

Embedded Systems

An embedded system is a combination of hardware and software designed to perform a specific, dedicated function within a larger device. Unlike a general-purpose computer, an embedded system is not designed to be reprogrammed for different tasks.

Examples: washing machine controller, pacemaker, car engine management unit, microwave oven, traffic light controller, digital camera
Typically contains a microcontroller with firmware stored in ROM
Optimised for low power consumption, reliability, and real-time response

Feature	Embedded system	General-purpose computer
Purpose	Single dedicated task	Many different tasks
User interaction	Minimal (buttons, sensors)	Full keyboard, mouse, screen
Software	Fixed firmware, rarely changed	User installs/runs any software
Power use	Very low	Higher

📝 Exam Tip: When asked to recommend an input device for a specific scenario, always justify your choice. E.g. "a barcode scanner is suitable for a supermarket because it quickly and accurately reads product codes without manual entry." Matching device to use case is key.

⚠️ Common Mistakes

Classifying a monitor as an input device — monitors are output only; a touchscreen monitor is both
Saying a printer is an input device — it is output only
Forgetting to explain how the device works — exam questions often ask "describe how" not just "name"