Cambridge (CIE) IGCSE Computer Science — Revision Notes#
An input device is any hardware that allows a user or environment to send data into a computer system for processing.Input Device = Hardware that converts real-world data into a digital signal the CPU can process.
⌨️ Keyboard#
The most common input device for entering text, numbers, and commands.
Uses a grid of keys — each key sends a unique signal to the CPU.
Types: standard QWERTY, ergonomic, virtual (on-screen).
🖱️ Mouse#
A pointing device used to control the cursor on screen.
Detects movement and sends X/Y coordinates to the CPU.
Has buttons and a scroll wheel for clicking and selecting.
Modern mice use optical or laser tracking (no rolling ball).
🕹️ Joystick#
Controls movement in two or more directions using a stick mechanism.
Sends directional and button-press signals to the CPU.
👆 Touch Screen#
Detects finger or stylus touch directly on the display surface.
Resistive — responds to pressure (older, cheaper).
Capacitive — responds to electrical charge of skin (modern smartphones).
✏️ Graphics Tablet (Digitiser)#
A flat surface on which a user draws using a stylus pen.
Converts the position and pressure of the pen into digital coordinates.
Provides much more precision than a mouse.
🖨️ Scanner (Flatbed)#
Captures a physical document or image and converts it to a digital file.
Uses a light source to illuminate the document and sensors to record reflected light.
Often combined with OCR software to convert scanned text into editable text.
📷 Digital Camera / Webcam#
Captures still images or video and stores them as digital files.
A webcam is a fixed camera connected to a computer (built-in or USB).
🔲 Barcode Reader#
Uses a laser or light to scan the pattern of black and white bars on a barcode.
Decodes the barcode into a number that is sent to the computer.
Types: handheld scanner, flatbed (supermarket checkout), smartphone camera.
🟦 QR Code Reader#
Reads a 2D matrix barcode using a camera or scanner.
Can store much more information than a standard barcode (URLs, text, contact info).
📄 OMR — Optical Mark Recognition#
Detects the presence or absence of marks in predefined positions on a form.
A light beam reflects off the paper — a mark reflects less light.
🔤 OCR — Optical Character Recognition#
Recognises printed or handwritten characters from a scanned image.
Converts the image of text into editable, machine-readable text.
🔢 MICR — Magnetic Ink Character Recognition#
Reads characters printed in magnetic ink on documents.
Highly secure and difficult to forge.
🎙️ Microphone#
Converts sound waves (air pressure changes) into electrical signals,
which are then converted to digital audio data.
Can be used for voice commands, recording, VoIP calls.
🖐️ Fingerprint Scanner#
Captures the unique ridge pattern of a fingerprint.
Compares it to a stored template for authentication.
👁️ Retina / Iris Scanner#
Captures the unique pattern of the retina or iris of the eye.
Extremely accurate — harder to spoof than fingerprints.
😊 Facial Recognition Camera#
Analyses the geometry of a face (distance between eyes, nose, jaw shape).
Matches against a stored facial template.
Sensors are input devices used mainly in embedded systems and automated processes.
They detect physical quantities and convert them into digital signals.| Sensor Type | What it Detects | Example Use |
|---|
| Temperature | Heat / cold levels | Thermostat, weather station |
| Pressure | Force applied to a surface | Airbag system, industrial machinery |
| Light (LDR) | Light intensity | Automatic street lighting |
| Infrared (IR) | Motion / heat from objects | Burglar alarm, automatic doors |
| Humidity | Moisture in the air | Greenhouse control, HVAC systems |
| Sound | Audio levels / vibration | Noise monitoring, security alarms |
| Proximity | Distance to an object | Parking sensors, robots |
| Accelerometer | Movement / orientation | Smartphone screen rotation, airbags |
Note: Sensors produce analogue signals which must be converted to digital by an
Analogue-to-Digital Converter (ADC) before the CPU can process them.
| Device | Type of Input | Analogue or Digital? | Key Advantage |
|---|
| Keyboard | Text / Commands | Digital | Fast text entry |
| Mouse | Position | Digital | Easy GUI navigation |
| Touch Screen | Position / Gesture | Digital | No separate device needed |
| Scanner | Image / Document | Digital | High-quality image capture |
| Barcode Reader | Product code | Digital | Fast and accurate |
| OMR Reader | Marks on paper | Digital | Very fast batch processing |
| OCR Reader | Printed text | Digital | Converts paper to editable text |
| MICR Reader | Magnetic ink text | Digital | Highly secure, hard to forge |
| Microphone | Sound | Analogue → Digital | Captures voice/audio |
| Fingerprint Scanner | Biometric | Digital | Unique to each person |
| Temperature Sensor | Heat | Analogue → Digital | Continuous real-time monitoring |
| Digital Camera | Image / Video | Digital | High-resolution image capture |
| Graphics Tablet | Drawing / Stylus | Digital | Pressure-sensitive, high precision |
10. Key Vocabulary#
| Term | Definition |
|---|
| Input Device | Hardware that sends data into a computer |
| OMR | Optical Mark Recognition — detects marks on paper |
| OCR | Optical Character Recognition — converts images of text to editable text |
| MICR | Magnetic Ink Character Recognition — reads magnetically printed characters |
| Biometric | Using a unique physical characteristic for identification |
| Sensor | Detects a physical quantity and converts it to an electrical signal |
| ADC | Analogue-to-Digital Converter — converts analogue sensor signals to digital |
| Firmware | Software stored in ROM that controls a device |
11. Exam Tips ✅#
Always justify your choice of input device — don't just name it, explain why it suits the scenario.
Know the difference between OMR and OCR — a very common exam question.
Remember that sensors produce analogue signals that need an ADC to convert to digital.
For biometric devices, mention both the capture step and the comparison step.
Touch screens are both input and output devices — screens display (output), touch detects (input).
MICR is almost exclusively associated with bank cheques in exam questions.
Cambridge (CIE) IGCSE Computer Science — 0478 / 0984Modified at 2026-04-03 09:51:20
