Keyboard

A keyboard's primary function is to act as an input device. Using a keyboard, a person can type a document, use keystroke shortcuts, access menus, play games and perform a variety of other tasks. Keyboards can have different keys depending on the manufacturer, the operating system they're designed for, and whether they are attached to a desktop computer or part of a laptop. But for the most part, these keys, also called keycaps, are the same size and shape from keyboard to keyboard. They're also placed at a similar distance from one another in a similar pattern, no matter what language or alphabet the keys represent.
Most keyboards have between 80 and 110 keys, including:

Typing keys
A numeric keypad
Function keys
Control keys

The typing keys include the letters of the alphabet, generally laid out in the same pattern used for typewriters. According to legend, this layout, known as QWERTY for its first six letters, helped keep mechanical typewriters' metal arms from colliding and jamming as people typed. Some people question this story – whether it’s true or not, the QWERTY pattern had long been a standard by the time computer keyboards came around.

Keyboards can also use a variety of other typing key arrangements. The most widely known is Dvorak, named for its creator, August Dvorak. The Dvorak layout places all of the vowels on the left side of the keyboard and the most common consonants on the right. The most commonly used letters are all found along the home row. The home row is the main row where you place your fingers when you begin typing. People who prefer the Dvorak layout say it increases their typing speed and reduces fatigue. Other layouts include ABCDE, XPeRT, QWERTZ and AZERTY. Each is named for the first keys in the pattern. The QWERTZ and AZERTY arrangements are commonly used in Europe.

The numeric keypad is a more recent addition to the computer keyboard. As the use of computers in business environments increased, so did the need for speedy data entry. Since a large part of the data was numbers, a set of 17 keys, arranged in the same configuration found on adding machines and calculators, was added to the keyboard.

The Apple keyboard's control keys include the "Command" key.
In 1986, IBM further extended the basic keyboard with the addition of function and control keys. Applications and operating systems can assign specific commands to the function keys. Control keys provide cursor and screen control. Four arrow keys arranged in an inverted T formation between the typing keys and numeric keypad move the cursor on the screen in small increments.

The Windows keyboard adds some extra control keys: two Windows or Start keys, and an Application key. Apple keyboards, on the other hand, have Command (also known as "Apple") keys. A keyboard developed for Linux users features Linux-specific hot keys, including one marked with "Tux" the penguin -- the Linux logo/mascot.

Keyboard Switches
Keyboards use a variety of switch technologies. Capacitive switches are considered to be non-mechanical because they do not physically complete a circuit like most other keyboard technologies. Instead, current constantly flows through all parts of the key matrix. Each key is spring-loaded and has a tiny plate attached to the bottom of it. When you press a key, it moves this plate closer to the plate below it. As the two plates move closer together, the amount of current flowing through the matrix changes. The processor detects the change and interprets it as a key press for that location. Capacitive switch keyboards are expensive, but they have a longer life than any other keyboard. Also, they do not have problems with bounce since the two surfaces never come into actual contact. All of the other types of switches used in keyboards are mechanical in nature. Each provides a different level of audible and tactile response -- the sounds and sensations that typing creates. Mechanical key switches include: