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Cambridge IGCSE Computer Science · 0478
Topic 3: Hardware — Part 2
Input & Output Devices
Input devices
- Barcode scanner
- Reads barcodes to identify products quickly using unique codes (e.g. at supermarket checkouts).
- Digital camera
- Captures photographs or videos as digital files.
- Keyboard
- Inputs text, numbers, and commands.
- Microphone
- Captures analogue sound and converts it to digital signals.
- Optical mouse
- Detects movement and clicks to control a screen pointer.
- QR code scanner
- Reads QR codes to access data like URLs or payment info.
- Scanners
- 2D scanners digitise flat documents (e.g. passports); 3D scanners capture the shape and appearance of 3D objects to create digital models.
Touch screens comparison
| Technology | Operation | Advantages | Disadvantages |
|---|---|---|---|
| Resistive | Works via pressure on two layers. | Cheap; can be used with gloves or a stylus. | Less responsive; easily scratched. |
| Capacitive | Works via electrical properties of a finger. | Highly responsive and accurate. | Cannot be used with standard gloves. |
| Infra-red | Uses a grid of beams to detect touch. | Durable; can detect any input object. | Screen can be affected by dust or dirt. |
Output devices
- Actuator
- Converts digital signals into real-world physical actions (e.g. opening automatic doors or moving robotic arms).
- Projectors
- DLP projectors use tiny mirrors and a light source; LCD projectors use liquid crystal panels to project images.
- Printers
- Inkjet printers spray tiny ink droplets (good for colour photos); laser printers use lasers and heat to fuse toner (fast for high-volume office use).
- 3D printer
- Builds physical objects layer by layer from digital models.
- Screens
- LCD screens use liquid crystals and a backlight; LED screens use light-emitting diodes and are brighter and more energy-efficient than LCD.
- Speaker
- Converts digital audio signals into audible sound.
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