Keyboard (computing)

In computing, a keyboard is an input device, partially modeled after the typewriter keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches. A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or computer commands.

In normal usage, the keyboard is used to type text and numbers into a word processor, text editor or other program. In a modern computer, the interpretation of keypresses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all keypresses to the controlling software. Keyboards are also used for computer gaming, either with regular keyboards or by using keyboards with special gaming features, which can expedite frequently used keystroke combinations. A keyboard is also used to give commands to the operating system of a computer, such as Windows' Control-Alt-Delete combination, which brings up a task window or shuts down the machine.



Types
Standard

Standard keyboards for desktop computers, such as the 101-key US traditional keyboards or the 104-key Windows keyboards, Include alphabetic characters, punctuation symbols, numbers and a variety of function keys. The internationally-common 102/105 key keyboards have a smaller 'left shift' key and an additional key with some more symbols between that and the letter to its right (usually Z or Y).[1] Computer keyboards are similar to electric-typewriter keyboards but contain additional keys.
Laptop-size

Keyboards on laptops and notebook computers usually have a shorter travel distance for the keystroke and a reduced set of keys. They may not have a numerical keypad, and the function keys may be placed in locations that differ from their placement on a standard, full-sized keyboard.
The keyboards on laptops have a shorter travel distance and (usually) a reduced set of keys.
Multimedia

Keyboards with extra keys, such as multimedia keyboards, have special keys for accessing music, web and other frequently used programs. For example, 'ctrl+marked on color-coded keys are used for some software applications and for specialized uses such as video editing.
Thumb-sized

Smaller keyboards have been introduced for laptops, PDAs, cellphones or users who have a limited workspace. The size of a standard keyboard is dictated by the practical consideration that the keys must be large enough to be easily pressed by fingers. To reduce the size of the keyboard, the numeric keyboard to the right of the alphabetic keyboard can be removed, or the size of the keys can be reduced, which makes it harder to enter text.

Another way to reduce the size of the keyboard is to reduce the number of keys and use chording keyer, i.e. pressing several keys simultaneously. For example, the GKOS keyboard has been designed for small wireless devices. Other two-handed alternatives more akin to a game controller, such as the AlphaGrip, are also used as a way to input data and text. Another way to reduce the size of a keyboard is to use smaller buttons and pack them closer together. Such keyboards, often called a "thumbboard" (thumbing) are used in some personal digital assistants such as the Palm Treo and BlackBerry and some Ultra-Mobile PCs such as the OQO.
Numeric

Numeric keyboards contain only numbers, mathematical symbols for addition, subtraction, multiplication, and division, a decimal point, and several function keys (e.g. End, Delete, etc.). They are often used to facilitate data entry with smaller keyboard-equipped laptops or with smaller keyboards that do not have a numeric keypad. A laptop does sometimes have a numeric pad, but not all the time. These keys are also known as, collectively, a numeric pad, numeric keys, or a numeric keypad, and it can consist of the following types of keys:

* arithmetic operators such as +, -, *, /
* numeric digits 0-9
* cursor arrow keys
* navigation keys such as Home, End, PgUp, PgDown, etc.
* Num Lock button, used to enable or disable the numeric pad
* enter key

Non-standard or special-use types
Chorded

A keyset or Virtual keyboards, such as the I-Tech Virtual Laser Keyboard, project an image of a full-size keyboard onto a surface. Sensors in the projection unit identify which key is being "pressed" and relay the signals to a computer or personal digital assistant. There is also a virtual keyboard, the On-Screen Keyboard, for use on Windows. The On-Screen Keyboard is an image of a standard keyboard which the user controls by using a mouse to hover over the desired letter or symbol, and then clicks to enter the letter. The On-Screen Keyboard is provided with Windows as an accessibility aid, to assist users who may have difficulties using a regular keyboard. The iPhone uses a multi-touch screen to display a virtual keyboard.
Touchscreens

Touchscreens, such as with the iPhone and the OLPC laptop, can be used as a keyboard. (The OLPC initiative's second computer will be effectively two tablet touchscreens hinged together like a book. It can be used as a convertible Tablet PC where the keyboard is one half-screen (one side of the book) which turns into a touchscreen virtual keyboard.)