What you'll learn
Input devices are essential hardware components that allow users to enter data and instructions into a computer system. This revision guide covers all input devices you need to know for the CIE IGCSE Computer Science examination, including their working principles, appropriate uses, advantages and disadvantages. You'll develop the skills to select the most suitable input device for specific scenarios and justify your choices using technical terminology.
Key terms and definitions
Input device — A hardware component that allows data and instructions to be entered into a computer system for processing.
Peripheral — An external device that connects to a computer to provide additional input, output or storage functionality.
Sensor — An input device that measures physical properties from the environment and converts them into electrical signals for computer processing.
Optical Character Recognition (OCR) — Technology that converts printed or handwritten text from scanned images into machine-readable digital text.
Optical Mark Recognition (OMR) — Technology that detects the presence or absence of marks on predetermined positions on a document, commonly used for multiple-choice answer sheets.
Magnetic Ink Character Recognition (MICR) — Technology that reads characters printed with magnetic ink, primarily used on bank cheques for secure and reliable processing.
Barcode reader — An input device that scans and interprets printed barcodes to retrieve product or item information stored as a series of parallel lines.
Biometric device — An input device that identifies individuals by measuring unique physical or behavioural characteristics such as fingerprints or iris patterns.
Core concepts
Manual input devices
Keyboard
The keyboard remains the most common text input device. Standard QWERTY keyboards contain alphanumeric keys, function keys, navigation keys and a numeric keypad.
Uses:
- Entering text for documents, emails and programming code
- Inputting commands and search queries
- Data entry in databases and spreadsheets
- Controlling computer functions through keyboard shortcuts
Advantages:
- Fast and accurate for experienced typists
- Suitable for entering complex data including symbols
- Widely understood with minimal training required
- Relatively inexpensive
Disadvantages:
- Requires typing skills for efficiency
- Slower than direct selection methods for some tasks
- Physical size limits portability
- Repetitive strain injury risk with prolonged use
Mouse
The mouse is a pointing device that controls an on-screen cursor through movement across a flat surface.
Uses:
- Selecting icons, buttons and menu items
- Drawing and graphic design work
- Playing computer games requiring pointing
- Navigating web pages and documents
Advantages:
- Intuitive and easy to learn
- Precise cursor positioning
- Quick selection of screen elements
- Suitable for graphical user interfaces
Disadvantages:
- Requires flat surface for operation
- Can cause repetitive strain injury
- Less suitable for text entry
- Difficult to use for users with limited mobility
Touchscreen
Touchscreens detect the position of touches on the display surface using capacitive or resistive technology.
Uses:
- Smartphones and tablets for all interactions
- Self-service kiosks in airports and shops
- Point-of-sale systems in retail
- Interactive whiteboards in education
- Satellite navigation systems in vehicles
Advantages:
- Direct interaction with displayed elements
- No additional input device required
- Intuitive for users of all ages
- Space-efficient design
- Easy to clean and maintain
Disadvantages:
- Screen becomes marked with fingerprints
- Lacks tactile feedback for typing
- Difficult to use with precision for detailed work
- Can be tiring to use for extended periods
- Gorilla arm effect when used vertically
Pointing and selection devices
Trackball and touchpad
Trackballs contain a ball rotated by the user's fingers to move the cursor. Touchpads detect finger movement across a touch-sensitive surface.
Trackball advantages:
- Stationary device requiring less desk space
- Precise control for detailed work
- Reduced arm movement compared to mice
Touchpad uses:
- Laptop computers as built-in pointing device
- Compact devices where space is limited
Graphics tablet
Graphics tablets use a stylus on a pressure-sensitive surface to create digital artwork or handwriting.
Uses:
- Digital art and illustration
- Photo retouching and editing
- Technical drawing and CAD work
- Handwriting recognition and digital signatures
Advantages:
- Natural drawing motion with stylus
- Pressure sensitivity for varied line thickness
- More precise than mouse for artistic work
- Reduces repetitive strain compared to mouse
Automated input devices
Barcode reader
Barcode readers use laser or LED light to scan printed barcodes, converting the pattern of lines into numerical data.
Uses:
- Point-of-sale systems in supermarkets and retail
- Library book tracking systems
- Warehouse stock control and inventory management
- Parcel tracking in logistics
- Patient identification in healthcare
Advantages:
- Fast and accurate data entry
- Reduces human input errors
- Eliminates need for manual keying
- Inexpensive to implement
- Standardised across industries
Disadvantages:
- Requires line of sight to scan
- Damaged barcodes cannot be read
- Limited data storage capacity
- Requires printed labels
QR code reader
QR codes store more data than traditional barcodes in a two-dimensional pattern. Cameras in smartphones typically read them.
Uses:
- Marketing materials linking to websites
- Product information and authentication
- Contactless payment systems
- Event ticketing and boarding passes
RFID reader
Radio Frequency Identification (RFID) readers detect radio signals from RFID tags without requiring line of sight.
Uses:
- Contactless payment cards
- Access control and security systems
- Animal tracking and pet identification
- Highway toll collection
- Passport control at borders
Advantages over barcodes:
- No line of sight required
- Can read multiple tags simultaneously
- Greater data storage capacity
- Tags can be read/write enabled
- More durable and secure
Disadvantages:
- More expensive than barcodes
- Privacy concerns with tracking
- Limited range without power source
- Potential interference issues
Document scanning devices
Optical scanners
Optical scanners convert physical documents and images into digital format using light sensors.
Uses:
- Creating digital copies of documents
- Scanning photographs for digital storage
- Archiving historical documents
- Capturing images for OCR processing
OCR applications:
- Converting scanned books into searchable text
- Processing business cards into contact databases
- Digitising historical archives
- Automatic number plate recognition (ANPR)
OMR scanner
OMR scanners detect pencil marks in predetermined positions on forms.
Uses:
- Multiple-choice examination answer sheets
- Lottery ticket processing
- Survey and questionnaire processing
- Attendance registers
Advantages:
- Very fast processing of multiple forms
- Accurate mark detection
- Eliminates manual data entry
- Suitable for large-scale data collection
MICR reader
MICR readers use magnetic sensors to read characters printed with iron oxide ink.
Uses:
- Bank cheque processing
- Processing financial documents
Advantages:
- Highly secure and difficult to forge
- Readable even when damaged or marked
- Fast processing in banking systems
- Standardised internationally
Disadvantages:
- Limited to specific applications
- Expensive specialist equipment
- Requires magnetic ink and special fonts
Sensors and measurement devices
Sensors automatically capture real-world measurements without human intervention.
Common sensor types and uses:
Temperature sensors:
- Greenhouse climate control systems
- Central heating thermostats
- Industrial process monitoring
- Refrigeration units
Pressure sensors:
- Weather monitoring stations
- Burglar alarm systems on doors/windows
- Automotive tyre pressure monitoring
- Industrial safety systems
Light sensors:
- Automatic street lighting
- Smartphone screen brightness adjustment
- Greenhouse light monitoring
- Security lighting systems
Humidity sensors:
- Greenhouse irrigation control
- Museum climate control
- Industrial drying processes
Motion/proximity sensors:
- Automatic doors at supermarkets
- Security alarm systems
- Automatic lighting activation
- Vehicle parking assistance
Sound sensors (microphones):
- Voice recognition systems
- Digital assistants (Alexa, Siri)
- Video conferencing
- Sound level monitoring
Advantages of sensors:
- Continuous automated monitoring
- Consistent measurements without human error
- Operate in hazardous environments
- Provide real-time data for immediate response
- Enable data logging for analysis
Disadvantages of sensors:
- Calibration required for accuracy
- Can be affected by environmental factors
- Hardware failure can cause system issues
- Initial setup costs
Biometric input devices
Biometric devices identify individuals using unique physical characteristics.
Fingerprint scanner
Captures and analyses ridge patterns on fingertips.
Uses:
- Smartphone unlocking
- Building access control
- Police identification systems
- Time and attendance recording
Retina/iris scanner
Analyses unique patterns in the eye.
Uses:
- High-security facility access
- Border control and immigration
- Banking security systems
Facial recognition
Analyses facial features and dimensions.
Uses:
- Smartphone unlocking (Face ID)
- Airport security and passport control
- Social media photo tagging
- Police surveillance systems
Advantages of biometric systems:
- Cannot be lost or forgotten like passwords
- Difficult to forge or steal
- Fast authentication process
- No need to remember codes
Disadvantages:
- Privacy and surveillance concerns
- Expensive to implement
- False rejections can occur
- Permanent compromise if biometric data stolen
- May fail due to injuries or changes to features
Microphones and cameras
Microphone
Converts sound waves into electrical signals for digital processing.
Uses:
- Voice recognition and dictation software
- Video calls and online meetings
- Voice commands to digital assistants
- Recording podcasts and audio content
- Gaming communication
Digital camera/webcam
Captures still images or video as digital files.
Uses:
- Video conferencing and online lessons
- Recording video content for streaming
- Security and surveillance monitoring
- Scanning QR codes and barcodes
- Medical imaging and diagnosis
- Capturing images for computer vision systems
Worked examples
Example 1
Question: A supermarket needs to update its checkout system. Describe two suitable input devices and justify your choices. [6 marks]
Model answer: A barcode reader would be suitable because it can quickly scan product codes on items, allowing fast identification of products and automatic retrieval of prices from the database. This speeds up the checkout process and reduces errors compared to manual price entry. [3 marks]
A touchscreen would be suitable for the cashier interface because it allows easy selection of options like payment methods or quantity adjustments through direct interaction with the display. It requires minimal training for staff and eliminates the need for a separate keyboard and mouse, saving counter space. [3 marks]
Mark scheme guidance: 1 mark for naming device, 2 marks for relevant justification showing understanding of use in context.
Example 2
Question: A greenhouse uses sensors to control the growing environment. Identify three types of sensor that could be used and describe how each would be used. [6 marks]
Model answer: A temperature sensor would measure the air temperature inside the greenhouse. If the temperature falls below a set threshold, the heating system would automatically activate. If it exceeds the maximum, ventilation windows could open. [2 marks]
A humidity sensor would measure moisture levels in the air. When humidity drops too low, the irrigation system would activate to water plants and increase moisture. [2 marks]
A light sensor would measure the amount of natural light available. When light levels are insufficient, artificial growing lights would automatically switch on to ensure plants receive adequate light for photosynthesis. [2 marks]
Example 3
Question: Compare the use of OMR and OCR for processing examination papers. [4 marks]
Model answer: OMR is suitable for multiple-choice answer sheets because it detects the presence of marks in specific predetermined positions, allowing very fast processing of thousands of papers. However, it can only handle simple mark-based responses. [2 marks]
OCR is suitable for written answers because it can convert handwritten or printed text into digital format for marking or storage. However, it is slower than OMR and less accurate with poor handwriting, requiring manual checking. [2 marks]
Common mistakes and how to avoid them
Confusing input and output devices — Remember input devices send data INTO the computer. Touchscreens are both input (touch) and output (display) devices, but emphasise the input function when discussing them as input devices.
Vague justifications — Don't just state "it's faster" or "it's more accurate." Always explain WHY in the context given, e.g., "barcode scanning is faster than manual entry because the cashier doesn't need to type prices, reducing checkout time."
Mixing up OCR, OMR and MICR — Learn the specific uses: OCR converts text, OMR detects marks in predetermined positions, MICR reads magnetic ink on cheques. Don't use these terms interchangeably.
Forgetting advantages AND disadvantages — Exam questions often ask for both. Prepare balanced points for each device. For example, touchscreens are intuitive but create fingerprints and lack tactile feedback.
Naming sensors incorrectly — Use precise terminology: "temperature sensor" not "thermometer," "light sensor" not "LDR" (too technical for IGCSE), "motion sensor" not just "sensor."
Not matching device to context — Always consider the specific scenario. A graphics tablet is excellent for digital art but inappropriate for data entry in a warehouse. Read the question carefully and justify your choice based on the requirements given.
Exam technique for "Hardware: input devices and their uses"
Command word "Identify" — Simply name the device, no explanation needed. One mark per device. "Barcode reader" or "Temperature sensor" is sufficient.
Command word "Describe" — Explain how the device works or how it's used. Typically 2 marks. Example: "A barcode reader uses laser light to scan the pattern of lines, converting this into numerical data that identifies the product."
Command word "Justify" or "Explain why" — Give reasons that link to the specific context in the question. Show advantages relevant to the scenario. Usually 2-3 marks. Structure: state the device, explain what it does, explain why this suits the situation.
Comparison questions — Create a balanced response covering both items. Use comparative language: "whereas," "however," "in contrast." Allocate marks equally between the two devices being compared.
Quick revision summary
Input devices allow data and instructions to enter a computer system. Manual devices include keyboards, mice, touchscreens and graphics tablets. Automated devices include barcode readers, RFID readers, and document scanners using OCR, OMR or MICR technology. Sensors measure physical properties like temperature, light, pressure and humidity for monitoring and control systems. Biometric devices identify individuals using fingerprints, iris patterns or facial features. Select input devices based on context, considering speed, accuracy, cost, ease of use and suitability for the specific application.