Unit I — Input Devices

An input device is any hardware component that allows a user to enter data, instructions, or commands into a computer. The input device converts human-understandable data into machine-readable binary form.

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Keyboard

• The most common input device.
• Contains alphanumeric keys, function keys (F1–F12), special keys (Ctrl, Alt, Shift), and navigation keys.
• Types: QWERTY, AZERTY, Dvorak layout keyboards; membrane keyboards, mechanical keyboards.

Mouse

• A pointing device that controls the on-screen cursor.
• Actions: Left-click (select), Right-click (context menu), Double-click, Scroll wheel.
• Types: Mechanical, Optical, Wireless, Trackball mouse.

Scanner

• Converts physical documents or images into digital format.
• Types:
• Flatbed Scanner — Most common; document placed on glass plate.
• Handheld Scanner — Portable; moved over the document manually.
• Barcode Scanner — Reads barcode patterns (used in shops).
• OMR (Optical Mark Reader) — Detects pencil/pen marks (used in MCQ sheets).
• OCR (Optical Character Reader) — Reads printed text and converts to editable form.

Joystick

• Used primarily for gaming and CAD applications.
• A lever that moves in multiple directions to control on-screen objects.

Microphone

• Converts sound/voice into digital audio signals.
• Used in voice recognition, VoIP calls, recording.

Touch Screen

• A display that doubles as an input device.
• Detects touch using capacitive or resistive technology.
• Used in smartphones, tablets, ATMs, kiosks.

Light Pen

• A pen-shaped device used to point to or draw on a CRT screen.
• Detects light emitted by the screen phosphor.

Digital Camera / Webcam

• Capture images and video as digital data.
• Widely used for video conferencing and documentation.

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Comparison Table

Key Takeaway: Input devices are the gateway through which data enters a computer. Each device is optimised for a specific type of input — text, pointing, scanning, or audio. Knowing each device's working principle and common use-case is important for exam questions.