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A computer keyboard
Wireless multimedial media center German-layout keyboard with trackball
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]
Laptop-size[]
Keyboards on laptops and notebook computers usually have a shorter travel distance for the keystroke and a reduced set of keys. As well, 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 a reduced set of keys.
Gaming and multimedia[]
Keyboards with extra keys, such as multimedia keyboards, have special keys for accessing music, web and other frequently used programs and. For example, 'ctrl+marked on color-coded keys are used for some software applications and for specialized uses 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
Non-standard or special-use types[]
Virtual=[]
- Main article: Virtual keyboard
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.)
Foldable[]
- Further information: Flexible electronics
Foldable (also called flexible) keyboards are made of soft plastic or silicone which can be rolled or folded on itself for travel.[2] When in use, these keyboards can conform to uneven surfaces, and are more resistant to liquids than standard keyboards. These can also be connected to portable devices and smartphones. Some models can be fully immersed in water, making them popular in hospitals and laboratories, as they can be disinfected.
A foldable keyboard.
Laser/Infrared[]
Some devices have recently been produced which project a keyboard layout onto any flat surface using a laser. These devices detect key presses via infrared, and can artificially produce the tapping or clicking sound of a physical keyboard through their software.
Layout[]
Alphabetic[]
- Main article: Keyboard layout
The 104-key PC US English QWERTY keyboard layout evolved from the standard typewriter keyboard, with extra keys for computing.
The Dvorak Simplified Keyboard layout arranges keys so that frequently used keys are easiest to press, which reduces muscle fatigue when typing common English.
There are a number of different arrangements of alphabetic, numeric, and punctuation symbols on keys. These different keyboard layouts arise mainly because different people need easy access to different symbols, either because they are inputting text in different languages, or because they need a specialized layout for mathematics, accounting, computer programming, or other purposes. Most of the more common keyboard layouts (QWERTY-based and similar) were designed in the era of the mechanical typewriters, so their ergonomics had to be slightly compromised in order to tackle some of the mechanical limitations of the typewriter.
As the letter-keys were attached to levers that needed to move freely, inventor Christopher Sholes developed the QWERTY layout to reduce the likelihood of jamming. With the advent of computers, lever jams are no longer an issue, but nevertheless, QWERTY layouts were adopted for electronic keyboards because they were widely used. Alternative layouts such as the Dvorak Simplified Keyboard and Colemak are not in widespread use.
The QWERTZ layout is fairly widely used in Germany and much of Central Europe. The main difference between it and QWERTY is that Y and Z are swapped, and most special characters such as brackets are replaced by diacritical characters.
Another situation takes place with “national” layouts. Keyboards designed for typing in Spanish have some characters shifted, to release the space for Ñ ñ; similarly, those for French and other European languages may have a special key for the character Ç ç . The AZERTY layout is used in France, Belgium and some neighbouring countries. It differs from the QWERTY layout in that the A and Q are swapped, the Z and W are swapped, and the M is moved from the right of N to the right of L (where colon/semicolon is on a US keyboard). The digits 0 to 9 are on the same keys, but to be typed the shift key must be pressed. The unshifted positions are used for accented characters.
Keyboards designed for non-English speaking markets may have special keys to switch between non-English typing and the Roman alphabet and vice-versa. In Japan, keyboards often can be switched between Japanese and the Roman alphabet, and the character ¥ (the Yen currency) is used instead of "\". In the Arab world, keyboards can often be switched between Arabic and English.
In bilingual regions of Canada and in the French-speaking province of Quebec, keyboards can often be switched between an English and a French-language keyboard; while both keyboards share the same QWERTY alphabetic layout, the French-language keyboard enables the user to type accented vowels such as "é" or "à" with a single keystroke. Using keyboards for other languages leads to a conflict: the image on the key does not correspond to the character. In such cases, each new language may require an additional label on the keys, because the standard keyboard layouts do not share even similar characters of different languages (see the example in the figure above).
Key types[]
Alphanumeric[]
A Hebrew keyboard lets the user type in both Hebrew and the Latin alphabet.
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A Greek keyboard lets the user type in both Greek and the Latin alphabet(Macbook Pro).
Alphabetical, numeric, and punctuation keys are used in the same fashion as a typewriter keyboard to enter their respective symbol into a word processing program, text editor, data spreadsheet, or other program. Many of these keys will produce different symbols when modifier keys or shift keys are pressed. The alphabetic characters become uppercase when the shift key or Caps Lock key is depressed. The numeric characters become symbols or punctuation marks when the shift key is depressed. The alphabetical, numeric, and punctuation keys can also have other functions when they are pressed at the same time as some modifier keys.
The Space bar is a horizontal bar in the lowermost row, which is significantly wider than other keys. Like the alphanumeric characters, it is also descended from the mechanical typewriter. Its main purpose is to enter the space between words during typing. It is large enough so that a thumb from either hand can use it easily. Depending on the operating system, when the space bar is used with a modifier key such as the control key, it may have functions such as resizing or closing the current window, half-spacing, or backspacing. In computer games and other applications the key has myriad uses in addition to its normal purpose in typing, such as jumping and adding marks to check boxes. In certain programs for playback of digital video, the space bar is used for pausing and resuming the playback.
Technology[]
Alternative text-entering methods[]
An on-screen keyboard controlled with the mouse can be used by users with limited mobility.
Optical character recognition (OCR) is preferable to rekeying for converting existing text that is already written down but not in machine-readable format (for example, a Linotype-composed book from the 1940s). In other words, to convert the text from an image to editable text (that is, a string of character codes), a person could re-type it, or a computer could look at the image and deduce what each character is. OCR technology has already reached an impressive state (for example, Google Book Search) and promises more for the future.
Speech recognition converts speech into machine-readable text (that is, a string of character codes). The technology has already reached an impressive state and is already implemented in various software products. For certain uses (e.g., transcription of medical or legal dictation; journalism; writing essays or novels) it is starting to replace the keyboard; however, it does not threaten to replace keyboards entirely anytime soon. It can, however, interpret commands (for example, "close window" or "undo that") in addition to text. Therefore, it has theoretical potential to replace keyboards entirely (whereas OCR replaces them only for a certain kind of task).
Pointing devices can be used to enter text or characters in contexts where using a physical keyboard would be inappropriate or impossible. These accessories typically present characters on a display, in a layout that provides fast access to the more frequently used characters or character combinations. Popular examples of this kind of input are Graffiti, Dasher and on-screen virtual keyboards.
Other issues[]
Physical injury[]
Proper ergonomic design of computer keyboard desks is necessary to prevent repetitive strain injuries, which can develop over time and can lead to long-term disability.[3]
The use of any keyboard may cause serious injury (that is, carpal tunnel syndrome or other repetitive strain injury) to hands, wrists, arms, neck or back. The risks of injuries can be reduced by taking frequent short breaks to get up and walk around a couple of times every hour. As well, users should vary tasks throughout the day, to avoid overuse of the hands and wrists. When inputting at the keyboard, a person should keep the shoulders relaxed with the elbows at the side, with the keyboard and mouse positioned so that reaching is not necessary. The chair height and keyboard tray should be adjusted so that the wrists are straight, and the wrists should not be rested on sharp table edges. Wrist or palm rests should not be used while typing.
Some Adaptive technology ranging from special keyboards, mouse replacements and pen tablet interfaces to speech recognition software can reduce the risk of injury. Pause software reminds the user to pause frequently. Switching to a much more ergonomic keyboard layout may reduce the risk of injury. Switching to a much more ergonomic mouse, such as a vertical mouse or joystick mouse may provide relief. Switching from using a mouse to using a stylus pen with graphic tablet or a trackpad such as a Smart Cat trackpad can lessen the repetitive strain on the arms and hands.
See also[]
Notes and references[]
- ↑ includeonly>"Standard Keyboard Layouts".
- ↑ http://www.ocia.net/reviews/atkeyboard/page1.shtml
- ↑ Berkeley Lab. Integrated Safety Management: Ergonomics. Website. Retrieved 9 July 2008.
External links[]
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