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📘 CIE IGCSE Computer Science – Input and Output Devices Notes

1️⃣ Input Devices

🔹 What is an Input Device?​

✅ Definition:​

An input device is a hardware device used to enter data or instructions into a computer system.

🔹 Why Input Devices Are Required:​

  • To allow users to interact with the computer
  • To enter data for processing
  • To control software and hardware

Types of Input Devices (You Must Know These)​

⌨️ Keyboard​

Purpose:​

  • Used to input text, numbers and commands.

Data Type:​

  • Text (alphanumeric data)

Example Use:​

  • Typing documents
  • Programming

Exam Tip:​

Mention alphanumeric data input for full marks.

🖱️ Optical Mouse​

Purpose:​

  • Controls pointer on screen.

How It Works:​

  • Uses LED or laser light to detect movement.

Data Type:​

  • Movement data
  • Click signals

🎤 Microphone​

Purpose:​

  • Inputs sound into a computer.

Data Type:​

  • Audio (analogue → converted to digital)

Example:​

  • Voice recording
  • Voice recognition systems

📷 Digital Camera​

Purpose:​

  • Captures still images and videos.

Data Type:​

  • Image data (bitmap/pixel data)

Example:​

  • Video conferencing
  • Photography

🏷️ Barcode Scanner

Purpose:​

  • Reads barcodes using reflected light.

Data Type:​

  • Numeric code

Example:​

  • Supermarkets
  • Warehouses

Advantage:​

  • Fast and accurate data entry
  • Reduces human error

🔳 QR Code Scanner​

Purpose:​

  • Reads QR codes (2D barcodes).

Data Type:​

  • Text, URL, contact details

Difference from Barcode:​

  • QR stores more data
  • Can store different data types

📱 Touch Screen​

Allows user to interact directly with screen.

Types of Touch Screens:​

1️⃣ Resistive​

  • Two flexible layers that touch when pressed.
  • Works with finger, stylus, glove.

✅ Cheaper
❌ Less sensitive
❌ Less durable

2️⃣ Capacitive​

  • Detects change in electrical field.
  • Needs conductive object (finger).

✅ More sensitive
✅ More durable
❌ More expensive

3️⃣ Infra-red (IR)​

  • Uses infrared light beams across screen.
  • Detects interruption of beams.

✅ Very durable
✅ Very accurate
❌ Expensive

🖼️ 2D Scanner

Purpose:​

  • Scans flat images/documents.

Data Type:​

  • Image data

Example:​

  • Scanning documents

🧱 3D Scanner​

Purpose:​

  • Scans physical objects.

Data Type:​

  • 3D shape data

Example:​

  • Engineering design
  • Medical modelling

2️⃣ Output Devices

🔹 What is an Output Device?​

✅ Definition:​

An output device is hardware that receives processed data from a computer and presents it to the user.

🔹 Why Required:​

  • To display results
  • To produce hard copies
  • To produce sound
  • To control external systems

Types of Output Devices

🖥️ LED Screen (Light Emitting Diode)​

Features:​

  • Uses LEDs for backlighting.
  • Brighter and more energy efficient.

🖥️ LCD Screen (Liquid Crystal Display)​

Features:​

  • Uses liquid crystals to form images.
  • Thin and lightweight.

📽️ LCD Projector​

  • Projects images using LCD technology.

📽️ DLP Projector (Digital Light Processing)​

  • Uses microscopic mirrors.
  • Produces sharper images than LCD projector.

🔊 Speaker​

Purpose:​

  • Outputs sound.

Data Type:​

  • Audio signals

🖨️ Inkjet Printer​

How It Works:​

  • Sprays tiny droplets of ink.

Advantages:​

  • Good for colour images
  • Cheaper initial cost

Disadvantages:​

  • Slower
  • Ink can smudge

🖨️ Laser Printer​

How It Works:​

  • Uses laser and toner powder.

Advantages:​

  • Faster
  • High-quality text
  • Good for high volume

Disadvantages:​

  • More expensive

🖨️ 3D Printer​

Purpose:​

  • Produces physical 3D objects.

How:​

  • Builds object layer by layer.

Example:​

  • Prototypes
  • Medical implants

⚙️ Actuator​

Definition:​

An actuator converts electrical signals into physical movement.

Example:​

  • Opening a valve
  • Moving a robotic arm

3️⃣ Sensors

🔹 What is a Sensor?​

✅ Definition:​

A sensor is an input device that detects physical changes in the environment and sends data to a computer system.

🔹 Purpose of Sensors:​

  • Monitor environment
  • Automatic control systems
  • Real-time data collection

Example:

  • Temperature sensor in thermostat
  • Light sensor in street lights

Types of Sensors (Very Important ⚠️)

You must know:

  • What data they capture
  • When they are used

🌡️ Temperature Sensor​

Captures:

  • Temperature data

Used in:

  • Air conditioning
  • Refrigerators

💡 Light Sensor​

Captures:

  • Light intensity

Used in:

  • Automatic street lights

🔊 Acoustic Sensor​

Captures:

  • Sound levels

Used in:

  • Noise monitoring

🧭 Magnetic Field Sensor​

Captures:

  • Magnetic field strength

Used in:

  • Compass in smartphones

📡 Infra-red Sensor​

Captures:

  • Infrared radiation

Used in:

  • Motion detection
  • Remote controls

📏 Pressure Sensor​

Captures:

  • Pressure

Used in:

  • Car tyre pressure monitoring

💧 Humidity Sensor​

Captures:

  • Moisture in air

Used in:

  • Weather stations

🌊 Flow Sensor​

Captures:

  • Liquid flow rate

Used in:

  • Water systems

🛢️ Level Sensor​

Captures:

  • Level of liquid

Used in:

  • Fuel tanks

🧪 pH Sensor​

Captures:

  • Acidity/alkalinity

Used in:

  • Water quality testing

🚗 Accelerometer​

Captures:

  • Acceleration/movement

Used in:

  • Smartphones
  • Car airbag systems

🚶 Proximity Sensor​

Captures:

  • Nearby objects

Used in:

  • Automatic doors

💨 Gas Sensor​

Captures:

  • Presence of gases

Used in:

  • Smoke detectors

🌱 Moisture Sensor​

Captures:

  • Soil moisture

Used in:

  • Smart irrigation systems

Selecting the Correct Sensor (Exam Skill)

Example Question:

Which sensor should be used in an automatic irrigation system?

Correct answer:
👉 Moisture sensor (detects soil moisture)

Important Differences

Sensor vs Actuator​

SensorActuator
Input deviceOutput device
Detects changesCauses movement
Sends data to systemCarries out action

⭐ Exam Tips

✔ Always state what type of data is captured
✔ Mention real-world example
✔ Know advantages and disadvantages of printers
✔ Compare resistive vs capacitive touch screens
✔ Know difference between barcode and QR
✔ Understand difference between LCD and LED

⭐ Common Exam Mistakes

❌ Calling a sensor an output device
❌ Confusing actuator and sensor
❌ Saying laser printer uses liquid ink
❌ Forgetting QR codes are 2D

⭐ Key Definitions to Memorise

  • Input device: Hardware used to enter data into a computer.
  • Output device: Hardware that presents processed data.
  • Sensor: Device that detects physical changes.
  • Actuator: Device that converts electrical signal into physical movement.
  • Resistive screen: Works by pressure.
  • Capacitive screen: Works by electrical field.

🎯 Final Advice for IGCSE

  1. Learn device purposes clearly.
  2. Know which data type is captured.
  3. Practice “select the most suitable device” questions.
  4. Use technical vocabulary.
  5. Always give examples.