Computer Input Devices: Keyboards and Mice
Keyboards
Overview
A keyboard is an input device with a set of keys. Each key, whether numeric or alphanumeric, generates a unique electrical signal when pressed. This signal is sent to the computer interface.
Keyboard Sections
Keyboards are typically divided into five sections:
- Main Keyboard: Contains alphanumeric characters.
- Navigation Keys: Includes arrow keys and other navigation buttons.
- Numeric Keypad: Contains number keys and arithmetic operators.
- Function Keys: Includes keys F1 through F12.
- System Keys: Controls keyboard functions (e.g., Caps Lock).
Some keyboards also feature multimedia control keys and indicator lights.
Keyboard Mechanics
Keys are arranged in a QWERTY layout and connected by a network of contacts. Keyboards have a memory buffer to store typed characters before sending them to the interface.
Keyboard Types
- PC/XT Keyboard (83 keys)
- AT Keyboard (84 keys)
- Enhanced Keyboard (101 keys): Added Ctrl, Alt, and additional Enter keys.
- Windows Keyboard (104 keys): Added Windows and context menu keys.
- Ergonomic Keyboards: Designed to prevent carpal tunnel syndrome, often with a split layout.
- Multimedia Keyboards: Feature dedicated media control keys.
- Wireless Keyboards: Connect via Bluetooth, infrared, or radio frequency.
- Laptop Keyboards: Compact keyboards often with an FN key for additional functions.
Keyboard Connections
Modern keyboards typically connect via USB or PS/2. Regular cleaning is essential for optimal performance.
Mice
Overview
A mouse is an input device used to select information on the display using X and Y coordinates. Introduced by Apple, it contains a sensor and a processor to track movement and calculate coordinates.
Mouse Types
- Mechanical Mouse (including trackballs): May have serial, PS/2, or USB interfaces.
- Optical Mouse: Uses a light source to track movement, capturing approximately 1500 images per second.
- Laser Mouse: Similar to optical mice but more precise, with higher resolution.
- Trackball Mouse: Stationary mice with a movable ball on top for precise control.
- Wireless Mouse: Can be optical or laser, connecting via Bluetooth, infrared, or radio frequency.
Other mouse types include 3D mice, touchpads, and head-tracking mice.
Traditional Mouse Components
- Ball: Rolls to generate movement.
- Rollers: Rotate based on ball movement, corresponding to X and Y coordinates.
- Roller Shafts: Connect to rollers and have optical encoding wheels.
- Optical Rotary Encoders: Contain holes that allow infrared light to pass through as the wheel rotates.
- Infrared and Optical Sensor: Detects flashes of infrared light to determine movement.
- Processor: Calculates coordinates and sends them to the interface.
- Buttons: Used for selecting options.
Mouse Connections
Mice can connect via serial, PS/2, or USB interfaces.