Input Devices and Their Role

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.

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What Is an Input Device?

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.

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Common Input Devices

Keyboard

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.

Mouse / Trackpad

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.

Microphone

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

Camera / Webcam

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

Barcode Scanner

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

Touchscreen

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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