3.2 Mouse and Keyboards

3.2.a Mouse

A mouse is a pointing device. It has two functions: Click and Controlling Cruiser. Note that a mouse can only know its relative position of moving.

Mechanical MouseOptical Mouse
Structure* Rubber Wheel
* 2 Roller sets, perpendicular to each other.
* Light beam and detector

* Light Beam and Detector (Detector more like a camera)

How it works1. The rubber wheel turns while the mouse moves.
2. This turns one or both rollers.
3. The detector detects the transmission of light through the holes on discs.
4. Information of movement is sent to computer.
1. A light beam falls onto the object surface.
2. Light is reflected back to the sensor.
3. The sensor takes successive image of the object surface.
4. By comparing the images in an image processing software, the movement can be deduced.
5. Information is sent to the computer.

3.2.b Keyboards

Structure of Keyboards:

A key matrix is laid under the keys. Pressing a key will cause a contact in specific intersection, resulting a closed circuit.

A microprocessor and ROM chip is inside the keyboard. It continuously checks the current – when the microprocessor detects a closed circuit, it can identify the specific intersection.

It then converts the result into character code, which is then transmitted to the processor.

Next page: 3.3 Screens


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