Computer Keyboard

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Computer keyboardFrom Wikipedia, the free encyclopediaA key being pressed on a computer keyboard.In computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches. Following the decline of punch cards and paper tape, interaction via teleprinter-style keyboards became the main input device for computers. acer laptop keyboardDespite the development of alternative input devices, such as the mouse, touchscreen, pen devices, character recognition and voice recognition, the keyboard remains the most commonly used and most versatile device used for direct (human) input into computers.A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol. acer laptop keyboardHowever, 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, apple laptop keyboard 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 key presses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all key presses 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. ASUS laptop keyboard Keyboards are the only way to enter commands on a command-line interface.Contents [hide] 1 History2 Keyboard types2.1 Standard2.2 Laptop-size2.3 Thumb-sized3 Non-standard layout and special-use types3.1 ChordedCompaq laptop keyboard3.2 Software3.3 Foldable3.4 Projection (as by laser)3.5 Optical keyboard technology4 Layout4.1 Alphabetic4.2 Key types4.2.1 Alphanumeric4.2.2 Modifiers4.2.3 Navigation and typing modes4.2.4 System commands4.2.5 Miscellaneous4.2.6 Multiple layouts4.2.7 Layout changing software5 IlluminationCompaq laptop keyboard6 Technology6.1 Key switches6.2 Control processor6.3 Connection types7 Alternative text-entering methods8 Other issues8.1 Keystroke logging8.2 Wireless keystroke loggingCompaq laptop keyboard8.3 Physical injury8.4 Health risks9 See also10 Notes and references11 External links[edit]History

While typewriters are the definitive ancestor of all key-based text entry devices, the computer keyboard as a device for electromechanical data entry and communication derives largely from the utility of two devices: teleprinters (or teletypes) and keypunches. It was through such devices that modern computer keyboards inherited their layouts. Dell laptop keyboardAs early as the 1870s, teleprinter-like devices were used to simultaneously type and transmit stock market text data from the keyboard across telegraph lines to stock ticker machines to be immediately copied and displayed onto ticker tape. The teleprinter, in its more contemporary form, was developed from 1903-1910 by American mechanical engineer Charles Krum and his son Howard, with early contributions by electrical engineer Frank Pearne. Fujitsu laptop keyboardEarlier models were developed separately by individuals such as Royal Earl House and Frederick G. Creed.Earlier, Herman Hollerith developed the first keypunch devices, which soon evolved to include keys for text and number entry akin to normal typewriters by the 1930s. Gateway laptop keyboardThe keyboard on the teleprinter played a strong role in point-to-point and point-to-multipoint communication for most of the 20th century, while the keyboard on the keypunch device played a strong role in data entry and storage for just as long. The development of the earliest computers incorporated electric typewriter keyboards: the development of the ENIAC computer incorporated a keypunch device as both the input and paper-based output device, Hp laptop keyboardwhile the BINAC computer also made use of an electromechanically-controlled typewriter for both data entry onto magnetic tape (instead of paper) and data output.From the 1940s until the late 1960s, typewriters were the main means of data entry and output for computing, Hp laptop keyboard becoming integrated into what were known as computer terminals. Because of the lack of pace of text-based terminals in comparison to the growth in data storage, processing and transmission, a general move toward video-based computer terminals was affected by the 1970s, starting with the Datapoint 3300 in 1967. Hp laptop keyboardThe keyboard remained the primary, most integrated computer peripheral well into the era of personal computing until the introduction of the mouse as a consumer device in 1984. By this time, text-exclusive user interfaces with sparse graphics gave way to comparatively-graphics-rich icons on screen. However, keyboards remain central to human-computer interaction to the present, Hp laptop keyboardeven as mobile personal computing devices such as smartphones and tablets adapt the keyboard as an optional virtual, touchscreen-based means of data entry.[edit]Keyboard types

One factor determining the size of a keyboard is the presence of duplicate keys, such as a separate numeric keyboard, for convenience. Hp laptop keyboardFurther the keyboard size depends on the extent to which a system is used where a single action is produced by a combination of subsequent or simultaneous keystrokes (with modifier keys, see below), or multiple pressing of a single key. A keyboard with few keys is called a keypad. See also text entry interface.Another factor determining the size of a keyboard is the size and spacing of the keys. Hp laptop keyboard Reduction is limited by the practical consideration that the keys must be large enough to be easily pressed by fingers. Alternatively a tool is used for pressing small keys.[edit]Standard

Computer keyboard in use for a Windows 7 Desktop ComputerStandard “full-travel” alphanumeric keyboards have keys that are on three-quarter inch centers (0.750 inches, 19.05 mm), and have a key travel of at least 0.150 inches (3.81 mm). Desktop computer keyboards, Hp laptop keyboardsuch 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). Hp laptop keyboard Also the ‘enter’ key is usually shaped differently.[1] Computer keyboards are similar to electric-typewriter keyboards but contain additional keys. Standard USB keyboards can also be connected to some non-desktop devices.[2][edit]Laptop-sizeKeyboards 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. Hp laptop keyboard

The keyboards on laptops usually have a shorter travel distance and a reduced set of keys.[edit]Thumb-sizedSmaller external keyboards have been introduced for devices without a built-in keyboard, such as PDAs, and smartphones. Small keyboards are also useful where there is a limited workspace. Hp laptop keyboardA chorded keyboard allows 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.IBM laptop keyboardA thumb keyboard (thumbboard) is used in some personal digital assistants such as the Palm Treo and BlackBerry and some Ultra-Mobile PCs such as the OQO.Numeric keyboards contain only numbers, mathematical symbols for addition, subtraction, multiplication, and division, a decimal point, and several function keys. They are often used to facilitate data entry with smaller keyboards that do not have a numeric keypad, commonly those of laptop computers. These keys are collectively known as a numeric pad, numeric keys, or a numeric keypad, and it can consist of the following types of keys: samsung laptop keyboardarithmetic operators such as +, -, *, /numeric digits 0âEUR”9cursor arrow keysnavigation keys such as Home, End, PgUp, PgDown, etc.Num Lock button, used to enable or disable the numeric padenter key.[edit]Non-standard layout and special-use types

[edit]ChordedWhile other keyboards generally associate one action with each key, sony laptop keyboard chorded keyboards associate actions with combinations of key presses. Since there are many combinations available, chorded keyboards can effectively produce more actions on a board with fewer keys. Court reporters’ stenotype machines use chorded keyboards to enable them to enter text much faster by typing a syllable with each stroke instead of one letter at a time. sony laptop keyboardThe fastest typists (as of 2007) use a stenograph, a kind of chorded keyboard used by most court reporters and closed-caption reporters. Some chorded keyboards are also made for use in situations where fewer keys are preferable, such as on devices that can be used with only one hand, Toshiba laptop keyboardand on small mobile devices that don’t have room for larger keyboards. Chorded keyboards are less desirable in many cases because it usually takes practice and memorization of the combinations to become proficient.[edit]SoftwareSoftware keyboards or on-screen keyboards often take the form of computer programs that display an image of a keyboard on the screen. Another input device such as a mouse or a touchscreen can be used to operate each virtual key to enter text. Software keyboards have become very popular in touchscreen enabled cell phones, due to the additional cost and space requirements of other types of hardware keyboards. Microsoft Windows, Mac OS X, and some varieties of Linux include on-screen keyboards that can be controlled with the mouse. Toshiba laptop keyboard[edit]FoldableFurther information: Flexible electronics

A foldable keyboard.Foldable (also called flexible) keyboards are made of soft plastic or silicone which can be rolled or folded on itself for travel.[3] When in use, Toshiba laptop keyboardthese 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.[edit]Projection (as by laser) TravelMate 2352LCi keyboardProjection keyboards project an image of keys, usually with a laser, onto a flat surface. The device then uses a camera or infrared sensor to “watch” where the user’s fingers move, and will count a key as being pressed when it “sees” the user’s finger touch the projected image. Projection keyboards can simulate a full size keyboard from a very small projector. Because the “keys’ are simply projected images, they cannot be felt when pressed. Users of projected keyboards often experience increased discomfort in their fingertips because of the lack of “give” when typing. A flat, non-reflective surface is also required for the keys to be projected onto. Most projection keyboards are made for use with PDAs due to their small form factor. TravelMate 2350 keyboard[edit]Optical keyboard technologyAlso known as photo-optical keyboard, light responsive keyboard, photo-electric keyboard and optical key actuation detection technology.An optical keyboard technology utilizes light emitting devices and photo sensors to optically detect actuated keys. Most commonly the emitters and sensors are located in the perimeter, mounted on a small PCB. The light is directed from side to side of the keyboard interior and it can only be blocked by the actuated keys. Most optical keyboards require at least 2 beams (most commonly vertical beam and horizontal beam) to determine the actuated key. TravelMate 2313LCi keyboard Some optical keyboards use a special key structure that blocks the light in a certain pattern, allowing only one beam per row of keys (most commonly horizontal beam).Further information: Keyboard technology[edit]Layout

[edit]AlphabeticMain article: Keyboard layout

The 104-key PC US English QWERTY keyboard layout evolved from the standard typewriter keyboard, with extra keys for computing. TravelMate 2310 keyboard

The Dvorak Simplified Keyboard layout arranges keys so that frequently used keys are easiest to press, which reduces muscle fatigue when typing common English. TravelMate 2300 keyboardThere 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. The United States keyboard layout is used as default in the currently most popular operating systems: Windows,[4] Mac OS X[5] and Linux.[6][7] The common QWERTY-based layout was designed in the era of the mechanical typewriters, so its ergonomics was compromised to allow for the mechanical limitations of the typewriter. TravelMate 2200 Series keyboardAs 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 usedTravelMate 2010 keyboard. Alternative layouts such as the Dvorak Simplified Keyboard are not in widespread use.The QWERTZ layout is 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 âEURoenationalâEUR

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