Keyboard.

• came from mechanical typewriters that didn't use electricity.
  
• were invented by U.S. mechanical engineer Chirstopher Latham Sholes.
• input device- you put information in your computer using the keyboard.
• keys of the keyboard called keycaps
• has 80-100 keys(typing keys, numeric keypad, funtion keys and control keys).
• has it's own processor.

The way keyboard works.

• uses a switch to pass the electrical signal to the processor.
• processor filters it
• the most of circuitry is rodused by the key matrix.

Character map.

• located in the ROM
• processor uses it to define the keys of the keys of the keyboard.

Switches of the keyboard.

• keyboard uses a lot of the switch tecnologies
• each key of the keyboard is spring-loaded and has a tiny plate attached to it
• by pressing the key you move the plate on the key closer to the plate on the keyboard
• as the two plates move closer to each other the amount of current flowing through the matrix changes
• the processor detects the changes and inturprit the signal as the key press
• the other switches that used in the keyboard are mechanical;
• Mechanical key switches include:

* Membrane
* Rubber dome
* Metal contact
* Foam element

• rubber domes quite are common; they use small flexible rubber dome with hard carbon center; they are inexpenive, good at use;
• membrane keyboards use the flat surface instead of the keycaps and don't produce the klicking sound; they are not very common;
• metal contact and foam element keyboards are much less common; they have the spring in each of the keycaps; after some time the contacts could wear out, so tht it's no longer good for use;