Keyboard

A keyboard is an input device that allows you to enter commands and / or data to a computer or digital device. The keyboard is connected to the computer via a serial port or USB. Basically, the keyboard is composed by a group of keys, similar to those of a typewriter, each corresponding to one or more key characters, functions or commands.

Pressing any key closes a switch that is inside the keyboard, this makes circuits encoders generate code E / S corresponding to the selected character, appearing on the screen if it is not a control character.
The term refers to numeric keypad keys set of numbers on the right side of some keyboards (not the numbers on the top row of letters). The keypads also refer to the numbers (and the corresponding letters) in mobile phones.

KEYBOARD FEATURES
Keyboards can have certain characteristics depending on the type of keyboard, as follows:
Wireless keypads that do not use cable to connect with the computer but using infrared or radio frequency.
Ergonomic keyboards, adapted to human physiology.
Keyboards with special functions, these depend on the manufacturer. May include additional keys to open the browser, control the volume of the PC, open the player, etc. They may also include a touchpad.

KEYPAD MODELS
Some keyboard models are:
XT Keyboard: 83 keys, with processor included in the keyboard. Without use today.
AT Keyboard: 83 keys, the processor is on the motherboard.
Expanded or improved Keyboard: 102 keys. 102 keys in the American version. More recently is 105 keys.
Types of connectors that use a keyboard
The keyboard connector types most common are:
5-pin DIN and 180.
MiniDIN.
USB.