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This lesson covers input devices — what they are, how they work, and how they are used in different contexts. This is part of OCR J277 Section 1.1.1, which requires you to understand the role of input and output devices within a computer system.
An input device is any hardware component that allows a user (or another system) to send data into a computer for processing. Input devices convert real-world actions (such as pressing a key, moving a mouse, or speaking) into digital data that the computer can understand and process.
| Feature | Detail |
|---|---|
| How it works | Each key press sends a unique electrical signal (key code) to the CPU |
| Use | Entering text, commands, shortcuts, and data |
| Types | Mechanical, membrane, virtual (on-screen) |
The keyboard is the most common input device for text-based data entry. When a key is pressed, an interrupt is generated that tells the CPU to process the key press.
| Feature | Detail |
|---|---|
| How it works | Detects movement (optical sensor or ball) and sends positional data to the CPU |
| Use | Navigating GUIs, selecting items, drawing |
| Types | Optical mouse, laser mouse, trackpad, trackball |
An optical mouse uses a small LED and sensor to detect movement across a surface. The sensor captures images of the surface thousands of times per second and calculates direction and speed.
| Feature | Detail |
|---|---|
| How it works | Converts sound waves into electrical signals, which are digitised using an ADC (analogue-to-digital converter) |
| Use | Voice recording, voice commands, video calls |
| Feature | Detail |
|---|---|
| How it works | Captures light through a lens onto an image sensor (CCD or CMOS), converting it into digital image data |
| Use | Video calls, security, photography, facial recognition |
| Feature | Detail |
|---|---|
| How it works | Emits a laser or LED light onto a barcode; the reflected light pattern is decoded into a number |
| Use | Retail (point of sale), inventory management, library systems |
| Feature | Detail |
|---|---|
| How it works | Detects the position of a finger or stylus on the screen using capacitive or resistive technology |
| Use | Smartphones, tablets, ATMs, self-service kiosks |
Capacitive touchscreens detect the electrical charge from a finger. Resistive touchscreens detect pressure when two layers are pressed together.
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