In computing, a keyboard is a typewriter-style device, which uses an adjustment of buttons or keys, to act as automated levers or cyberbanking switches. Following the abatement of bite cards and cardboard tape, alternation via teleprinter-style keyboards became the capital ascribe accessory for computers.
A keyboard about has characters engraved or printed on the keys and anniversary columnist of a key about corresponds to a individual accounting symbol. However, to aftermath some symbols requires acute and captivation several keys accompanying or in sequence. While a lot of keyboard keys aftermath letters, numbers or signs (characters), added keys or accompanying key presses can aftermath accomplishments or computer commands.
Despite the development of another ascribe devices, such as the mouse, touchscreen, pen devices, appearance acceptance and articulation recognition, the keyboard charcoal the a lot of frequently acclimated and a lot of able accessory acclimated for absolute (human) ascribe into computers.
In accustomed usage, the keyboard is acclimated to blazon argument and numbers into a chat processor, argument editor or added programs. In a avant-garde computer, the estimation of key presses is about larboard to the software. A computer keyboard distinguishes anniversary concrete key from every added and letters all key presses to the authoritative software. Keyboards are aswell acclimated for computer gaming, either with approved keyboards or by application keyboards with appropriate gaming features, which can accelerate frequently acclimated keystroke combinations. A keyboard is aswell acclimated to accord commands to the operating arrangement of a computer, such as Windows' Control-Alt-Delete combination, which brings up a assignment window or shuts down the machine. Keyboards are the alone way to access commands on a command-line interface
Monday, December 17, 2012
History
While typewriters are the absolute antecedent of all key-based argument access devices, the computer keyboard as a accessory for electromechanical abstracts access and advice derives abundantly from the account of two devices: teleprinters (or teletypes) and keypunches. It was through such accessories that avant-garde computer keyboards affiliated their layouts.
As aboriginal as the 1870s, teleprinter-like accessories were acclimated to accompanying blazon and address banal bazaar argument abstracts from the keyboard beyond telegraph curve to banal ticker machines to be anon afflicted and displayed assimilate ticker tape. The teleprinter, in its added abreast form, was developed from 1903–1910 by American automated architect Charles Krum and his son Howard, with aboriginal contributions by electrical architect Frank Pearne. Earlier models were developed alone by individuals such as Royal Earl House and Frederick G. Creed.
Earlier, Herman Hollerith developed the aboriginal keypunch devices, which anon acquired to cover keys for argument and amount access affiliated to accustomed typewriters by the 1930s.
The keyboard on the teleprinter played a able role in point-to-point and point-to-multipoint advice for a lot of of the 20th century, while the keyboard on the keypunch accessory played a able role in abstracts access and accumulator for just as long. The development of the ancient computers congenital electric typewriter keyboards: the development of the ENIAC computer congenital a keypunch accessory as both the ascribe and paper-based achievement device, while the BINAC computer aswell fabricated use of an electromechanically controlled typewriter for both abstracts access assimilate alluring band (instead of paper) and abstracts output.
From the 1940s until the backward 1960s, typewriters were the capital agency of abstracts access and achievement for computing, acceptable chip into what were accepted as computer terminals. Because of the abridgement of clip of text-based terminals in allegory to the advance in abstracts storage, processing and transmission, a accepted move against video-based computer terminals was afflicted by the 1970s, starting with the Datapoint 3300 in 1967.
The keyboard remained the primary, a lot of chip computer borderline able-bodied into the era of claimed accretion until the addition of the abrasion as a customer accessory in 1984. By this time, text-only user interfaces with dispersed cartoon gave way to analogously graphics-rich icons on screen. However, keyboards abide axial to human-computer alternation to the present, even as adaptable claimed accretion accessories such as smartphones and tablets acclimate the keyboard as an alternative virtual, touchscreen-based agency of abstracts entry.
As aboriginal as the 1870s, teleprinter-like accessories were acclimated to accompanying blazon and address banal bazaar argument abstracts from the keyboard beyond telegraph curve to banal ticker machines to be anon afflicted and displayed assimilate ticker tape. The teleprinter, in its added abreast form, was developed from 1903–1910 by American automated architect Charles Krum and his son Howard, with aboriginal contributions by electrical architect Frank Pearne. Earlier models were developed alone by individuals such as Royal Earl House and Frederick G. Creed.
Earlier, Herman Hollerith developed the aboriginal keypunch devices, which anon acquired to cover keys for argument and amount access affiliated to accustomed typewriters by the 1930s.
The keyboard on the teleprinter played a able role in point-to-point and point-to-multipoint advice for a lot of of the 20th century, while the keyboard on the keypunch accessory played a able role in abstracts access and accumulator for just as long. The development of the ancient computers congenital electric typewriter keyboards: the development of the ENIAC computer congenital a keypunch accessory as both the ascribe and paper-based achievement device, while the BINAC computer aswell fabricated use of an electromechanically controlled typewriter for both abstracts access assimilate alluring band (instead of paper) and abstracts output.
From the 1940s until the backward 1960s, typewriters were the capital agency of abstracts access and achievement for computing, acceptable chip into what were accepted as computer terminals. Because of the abridgement of clip of text-based terminals in allegory to the advance in abstracts storage, processing and transmission, a accepted move against video-based computer terminals was afflicted by the 1970s, starting with the Datapoint 3300 in 1967.
The keyboard remained the primary, a lot of chip computer borderline able-bodied into the era of claimed accretion until the addition of the abrasion as a customer accessory in 1984. By this time, text-only user interfaces with dispersed cartoon gave way to analogously graphics-rich icons on screen. However, keyboards abide axial to human-computer alternation to the present, even as adaptable claimed accretion accessories such as smartphones and tablets acclimate the keyboard as an alternative virtual, touchscreen-based agency of abstracts entry.
Keyboard types
One agency free the admeasurement of a keyboard is the attendance of alike keys, such as a abstracted numeric keyboard, for convenience.
Further the keyboard admeasurement depends on the admeasurement to which a arrangement is acclimated area a individual activity is produced by a aggregate of consecutive or accompanying keystrokes (with modifier keys, see below), or assorted acute of a individual key. A keyboard with few keys is alleged a keypad. See aswell argument access interface.
Another agency free the admeasurement of a keyboard is the admeasurement and agreement of the keys. Reduction is bound by the applied application that the keys accept to be ample abundant to be calmly apprenticed by fingers. Alternatively a apparatus is acclimated for acute baby keys.
Standard
Computer keyboard in use for a Windows 7 Desktop Computer
Standard "full-travel" alphanumeric keyboards accept keys that are on three-quarter inch centers (0.750 inches, 19.05 mm), and accept a key biking of at atomic 0.150 inches (3.81 mm). Desktop computer keyboards, such as the 101-key US acceptable keyboards or the 104-key Windows keyboards, cover alphabetic characters, punctuation symbols, numbers and a array of action keys. The internationally accepted 102/105 key keyboards accept a abate larboard about-face key and an added key with some added symbols amid that and the letter to its appropriate (usually Z or Y). Aswell the access key is usually shaped differently.1 Computer keyboards are agnate to electric-typewriter keyboards but accommodate added keys. Accepted USB keyboards can aswell be affiliated to some non-desktop devices.2
Laptop-size
Keyboards on laptops and anthology computers usually accept a beneath biking ambit for the keystroke and a bargain set of keys. They may not accept a after keypad, and the action keys may be placed in locations that alter from their adjustment on a standard, full-sized keyboard.
The keyboards on laptops usually accept a beneath biking ambit and a bargain set of keys.
Thumb-sized
Smaller alien keyboards accept been alien for accessories after a congenital keyboard, such as PDAs, and smartphones. Baby keyboards are aswell advantageous area there is a bound workspace.
A chorded keyboard allows acute several keys simultaneously. For example, the GKOS keyboard has been advised for baby wireless devices. Other two-handed alternatives added affiliated to a bold controller, such as the AlphaGrip, are aswell acclimated as a way to ascribe abstracts and text.
A deride keyboard (thumbboard) is acclimated in some claimed agenda administration such as the Palm Treo and BlackBerry and some Ultra-Mobile PCs such as the OQO.
Numeric keyboards accommodate alone numbers, algebraic symbols for addition, subtraction, multiplication, and division, a decimal point, and several action keys. They are generally acclimated to facilitate abstracts access with abate keyboards that do not accept a numeric keypad, frequently those of laptop computers. These keys are collectively accepted as a numeric pad, numeric keys, or a numeric keypad, and it can abide of the afterward types of keys:
addition operators such as +, -, *, /
numeric digits 0–9
cursor arrow keys
aeronautics keys such as Home, End, PgUp, PgDown, etc.
Num Lock button, acclimated to accredit or attenuate the numeric pad
access key
Further the keyboard admeasurement depends on the admeasurement to which a arrangement is acclimated area a individual activity is produced by a aggregate of consecutive or accompanying keystrokes (with modifier keys, see below), or assorted acute of a individual key. A keyboard with few keys is alleged a keypad. See aswell argument access interface.
Another agency free the admeasurement of a keyboard is the admeasurement and agreement of the keys. Reduction is bound by the applied application that the keys accept to be ample abundant to be calmly apprenticed by fingers. Alternatively a apparatus is acclimated for acute baby keys.
Standard
Computer keyboard in use for a Windows 7 Desktop Computer
Standard "full-travel" alphanumeric keyboards accept keys that are on three-quarter inch centers (0.750 inches, 19.05 mm), and accept a key biking of at atomic 0.150 inches (3.81 mm). Desktop computer keyboards, such as the 101-key US acceptable keyboards or the 104-key Windows keyboards, cover alphabetic characters, punctuation symbols, numbers and a array of action keys. The internationally accepted 102/105 key keyboards accept a abate larboard about-face key and an added key with some added symbols amid that and the letter to its appropriate (usually Z or Y). Aswell the access key is usually shaped differently.1 Computer keyboards are agnate to electric-typewriter keyboards but accommodate added keys. Accepted USB keyboards can aswell be affiliated to some non-desktop devices.2
Laptop-size
Keyboards on laptops and anthology computers usually accept a beneath biking ambit for the keystroke and a bargain set of keys. They may not accept a after keypad, and the action keys may be placed in locations that alter from their adjustment on a standard, full-sized keyboard.
The keyboards on laptops usually accept a beneath biking ambit and a bargain set of keys.
Thumb-sized
Smaller alien keyboards accept been alien for accessories after a congenital keyboard, such as PDAs, and smartphones. Baby keyboards are aswell advantageous area there is a bound workspace.
A chorded keyboard allows acute several keys simultaneously. For example, the GKOS keyboard has been advised for baby wireless devices. Other two-handed alternatives added affiliated to a bold controller, such as the AlphaGrip, are aswell acclimated as a way to ascribe abstracts and text.
A deride keyboard (thumbboard) is acclimated in some claimed agenda administration such as the Palm Treo and BlackBerry and some Ultra-Mobile PCs such as the OQO.
Numeric keyboards accommodate alone numbers, algebraic symbols for addition, subtraction, multiplication, and division, a decimal point, and several action keys. They are generally acclimated to facilitate abstracts access with abate keyboards that do not accept a numeric keypad, frequently those of laptop computers. These keys are collectively accepted as a numeric pad, numeric keys, or a numeric keypad, and it can abide of the afterward types of keys:
addition operators such as +, -, *, /
numeric digits 0–9
cursor arrow keys
aeronautics keys such as Home, End, PgUp, PgDown, etc.
Num Lock button, acclimated to accredit or attenuate the numeric pad
access key
Non-standard layout and special-use types
Chorded
While added keyboards about accessory one activity with anniversary key, chorded keyboards accessory accomplishments with combinations of key presses. Since there are abounding combinations available, chorded keyboards can finer aftermath added accomplishments on a lath with beneath keys. Cloister reporters' stenotype machines use chorded keyboards to accredit them to access argument abundant faster by accounting a affricate with anniversary achievement instead of one letter at a time. The fastest typists (as of 2007) use a stenograph, a affectionate of chorded keyboard acclimated by a lot of cloister reporters and closed-caption reporters. Some chorded keyboards are aswell fabricated for use in situations area beneath keys are preferable, such as on accessories that can be acclimated with alone one hand, and on baby adaptable accessories that don't accept allowance for beyond keyboards. Chorded keyboards are beneath adorable in abounding cases because it usually takes convenance and anamnesis of the combinations to become proficient.
Software
Software keyboards or on-screen keyboards generally yield the anatomy of computer programs that affectation an angel of a keyboard on the screen. Another ascribe accessory such as a abrasion or a touchscreen can be acclimated to accomplish anniversary basic key to access text. Software keyboards accept become actual accepted in touchscreen enabled corpuscle phones, due to the added amount and amplitude requirements of added types of accouterments keyboards. Microsoft Windows, Mac OS X, and some varieties of Linux cover on-screen keyboards that can be controlled with the mouse.
Foldable
Further information: Adjustable electronics
A foldable keyboard.
Foldable (also alleged flexible) keyboards are fabricated of bendable artificial or silicone which can be formed or bankrupt on itself for travel.3 If in use, these keyboards can accommodate to asperous surfaces, and are added aggressive to liquids than accepted keyboards. These can aswell be affiliated to carriageable accessories and smartphones. Some models can be absolutely absorbed in water, authoritative them accepted in hospitals and laboratories, as they can be disinfected.
Projection (as by laser)
Projection keyboards activity an angel of keys, usually with a laser, assimilate a collapsed surface. The accessory again uses a camera or bittersweet sensor to "watch" area the user's fingers move, and will calculation a key as getting apprenticed if it "sees" the user's feel blow the projected image. Bump keyboards can simulate a abounding admeasurement keyboard from a actual baby projector. Because the "keys" are artlessly projected images, they cannot be acquainted if pressed. Users of projected keyboards generally acquaintance added ache in their fingertips because of the abridgement of "give" if typing. A flat, non-reflective apparent is aswell appropriate for the keys to be projected. A lot of bump keyboards are fabricated for use with PDAs and smartphones due to their baby anatomy factor.
Optical keyboard technology
Also accepted as photo-optical keyboard, ablaze acknowledging keyboard, photo-electric keyboard and optical key actuation apprehension technology.
An optical keyboard technology utilizes ablaze abounding accessories and photo sensors to optically ascertain actuated keys. A lot of frequently the emitters and sensors are amid in the perimeter, army on a baby PCB. The ablaze is directed from ancillary to ancillary of the keyboard autogenous and it can alone be blocked by the actuated keys. A lot of optical keyboards crave at atomic 2 beams (most frequently vertical axle and accumbent beam) to actuate the actuated key. Some optical keyboards use a appropriate key anatomy that blocks the ablaze in a assertive pattern, acceptance alone one axle per row of keys (most frequently accumbent beam).
While added keyboards about accessory one activity with anniversary key, chorded keyboards accessory accomplishments with combinations of key presses. Since there are abounding combinations available, chorded keyboards can finer aftermath added accomplishments on a lath with beneath keys. Cloister reporters' stenotype machines use chorded keyboards to accredit them to access argument abundant faster by accounting a affricate with anniversary achievement instead of one letter at a time. The fastest typists (as of 2007) use a stenograph, a affectionate of chorded keyboard acclimated by a lot of cloister reporters and closed-caption reporters. Some chorded keyboards are aswell fabricated for use in situations area beneath keys are preferable, such as on accessories that can be acclimated with alone one hand, and on baby adaptable accessories that don't accept allowance for beyond keyboards. Chorded keyboards are beneath adorable in abounding cases because it usually takes convenance and anamnesis of the combinations to become proficient.
Software
Software keyboards or on-screen keyboards generally yield the anatomy of computer programs that affectation an angel of a keyboard on the screen. Another ascribe accessory such as a abrasion or a touchscreen can be acclimated to accomplish anniversary basic key to access text. Software keyboards accept become actual accepted in touchscreen enabled corpuscle phones, due to the added amount and amplitude requirements of added types of accouterments keyboards. Microsoft Windows, Mac OS X, and some varieties of Linux cover on-screen keyboards that can be controlled with the mouse.
Foldable
Further information: Adjustable electronics
A foldable keyboard.
Foldable (also alleged flexible) keyboards are fabricated of bendable artificial or silicone which can be formed or bankrupt on itself for travel.3 If in use, these keyboards can accommodate to asperous surfaces, and are added aggressive to liquids than accepted keyboards. These can aswell be affiliated to carriageable accessories and smartphones. Some models can be absolutely absorbed in water, authoritative them accepted in hospitals and laboratories, as they can be disinfected.
Projection (as by laser)
Projection keyboards activity an angel of keys, usually with a laser, assimilate a collapsed surface. The accessory again uses a camera or bittersweet sensor to "watch" area the user's fingers move, and will calculation a key as getting apprenticed if it "sees" the user's feel blow the projected image. Bump keyboards can simulate a abounding admeasurement keyboard from a actual baby projector. Because the "keys" are artlessly projected images, they cannot be acquainted if pressed. Users of projected keyboards generally acquaintance added ache in their fingertips because of the abridgement of "give" if typing. A flat, non-reflective apparent is aswell appropriate for the keys to be projected. A lot of bump keyboards are fabricated for use with PDAs and smartphones due to their baby anatomy factor.
Optical keyboard technology
Also accepted as photo-optical keyboard, ablaze acknowledging keyboard, photo-electric keyboard and optical key actuation apprehension technology.
An optical keyboard technology utilizes ablaze abounding accessories and photo sensors to optically ascertain actuated keys. A lot of frequently the emitters and sensors are amid in the perimeter, army on a baby PCB. The ablaze is directed from ancillary to ancillary of the keyboard autogenous and it can alone be blocked by the actuated keys. A lot of optical keyboards crave at atomic 2 beams (most frequently vertical axle and accumbent beam) to actuate the actuated key. Some optical keyboards use a appropriate key anatomy that blocks the ablaze in a assertive pattern, acceptance alone one axle per row of keys (most frequently accumbent beam).
Layout
Alphabetic
Main article: Keyboard layout
The 104-key PC US English QWERTY keyboard blueprint acquired from the accepted typewriter keyboard, with added keys for computing.
The Dvorak Simplified Keyboard blueprint arranges keys so that frequently acclimated keys are easiest to press, which reduces beef fatigue if accounting accepted English.
There are a amount of altered arrange of alphabetic, numeric, and punctuation symbols on keys. These altered keyboard layouts appear mainly because altered humans charge simple admission to altered symbols, either because they are inputting argument in altered languages, or because they charge a specialized blueprint for mathematics, accounting, computer programming, or added purposes. The United States keyboard blueprint is acclimated as absence in the currently a lot of accepted operating systems: Windows,4 Mac OS X5 and Linux.67 The accepted QWERTY-based blueprint was advised aboriginal in the era of automated typewriters, so its ergonomics were compromised to acquiesce for the automated limitations of the typewriter.
As the letter-keys were absorbed to levers that bare to move freely, artist Christopher Sholes developed the QWERTY blueprint to abate the likelihood of jamming. With the appearance of computers, batten jams are no best an issue, but nevertheless, QWERTY layouts were adopted for cyberbanking keyboards because they were broadly used. Alternative layouts such as the Dvorak Simplified Keyboard are not in boundless use.
The QWERTZ blueprint is broadly acclimated in Germany and abundant of Central Europe. The capital aberration amid it and QWERTY is that Y and Z are swapped, and a lot of appropriate characters such as brackets are replaced by diacritical characters.
Another bearings takes abode with "national" layouts. Keyboards advised for accounting in Spanish accept some characters shifted, to absolution the amplitude for Г‘ Г±; similarly, those for French and added European languages may accept a appropriate key for the appearance Г‡ Г§. The AZERTY blueprint is acclimated in France, Belgium and some neighbouring countries. It differs from the QWERTY blueprint in that the A and Q are swapped, the Z and W are swapped, and the M is confused from the appropriate of N to the appropriate of L (where colon/semicolon is on a US keyboard). The digits 0 to 9 are on the aforementioned keys, but to be typed the about-face key accept to be pressed. The unshifted positions are acclimated for absolute characters.
Keyboards in abounding locations of Asia may accept appropriate keys to about-face amid the Latin appearance set and a absolutely altered accounting system. Japanese blueprint keyboards can be switched amid assorted Japanese ascribe methods and the Latin alphabet by signaling the operating system's ascribe analyst of the change, and some operating systems (namely the Windows family) adapt the appearance "" as "ВҐ" for affectation purposes afterwards alteration the bytecode which has led some keyboard makers to mark "" as "ВҐ" or both. In the Arab world, keyboards can generally be switched amid Arabic and Latin characters.
In bilingual regions of Canada and in the French-speaking arena of QuГ©bec, keyboards can generally be switched amid an English and a French-language keyboard; while both keyboards allotment the aforementioned QWERTY alphabetic layout, the French-language keyboard enables the user to blazon absolute vowels such as "Г©" or "Г " with a individual keystroke. Application keyboards for added languages leads to a conflict: the angel on the key does not accord to the character. In such cases, anniversary new emphasis may crave an added characterization on the keys, because the accepted keyboard layouts do not allotment even agnate characters of altered languages (see the archetype in the amount above).
Key types
Alphanumeric
A Hebrew keyboard lets the user blazon in both Hebrew and the Latin alphabet.
A Greek keyboard lets the user blazon in both Greek and the Latin alphabet (Macbook Pro).
The Ascendancy and Alt keys are important modifier keys.
A Space-cadet keyboard has abounding modifier keys.
Alphabetical, numeric, and punctuation keys are acclimated in the aforementioned appearance as a typewriter keyboard to admission their corresponding attribute into a chat processing program, argument editor, abstracts spreadsheet, or added program. Abounding of these keys will aftermath altered symbols if modifier keys or about-face keys are pressed. The alphabetic characters become uppercase if the about-face key or Caps Lock key is depressed. The numeric characters become symbols or punctuation marks if the about-face key is depressed. The alphabetical, numeric, and punctuation keys can aswell accept added functions if they are apprenticed at the aforementioned time as some modifier keys.
The Amplitude bar is a accumbent bar in the basal row, which is decidedly added than added keys. Like the alphanumeric characters, it is aswell descended from the automated typewriter. Its capital purpose is to admission the amplitude amid words during typing. It is ample abundant so that a deride from either duke can use it easily. Depending on the operating system, if the amplitude bar is acclimated with a modifier key such as the ascendancy key, it may accept functions such as resizing or closing the accepted window, half-spacing, or backspacing. In computer amateur and added applications the key has countless uses in accession to its accustomed purpose in typing, such as jumping and abacus marks to analysis boxes. In assertive programs for playback of agenda video, the amplitude bar is acclimated for pausing and resuming the playback.
Modifiers
Modifier keys are appropriate keys that adapt the accustomed activity of accession key, if the two are apprenticed in combination. For example, + in Microsoft Windows will abutting the affairs in an alive window. In contrast, acute just will apparently do nothing, unless assigned a specific action in a accurate program. By themselves, modifier keys usually do nothing.
The a lot of broadly acclimated modifier keys cover the Ascendancy key, About-face key and the Alt key. The AltGr key is acclimated to admission added symbols for keys that accept three symbols printed on them. On the Macintosh and Apple keyboards, the modifier keys are the Option key and Command key, respectively. On MIT computer keyboards, the Meta key is acclimated as a modifier and for Windows keyboards, there is a Windows key. Compact keyboard layouts generally use a Fn key. "Dead keys" acquiesce adjustment of a characteristic mark, such as an accent, on the afterward letter (e.g., the Compose key).
The Enter/Return key about causes a command line, window anatomy or chat box to accomplish its absence function, which is about to accomplishment an "entry" and activate the adapted process. In chat processing applications, acute the admission key ends a branch and starts a new one.
Navigation and accounting modes
Navigation keys cover a array of keys which move the cursor to altered positions on the screen. Arrow keys are programmed to move the cursor in a defined direction; page annal keys, such as the Page Up and Page Down keys, annal the page up and down. The Home key is acclimated to acknowledgment the cursor to the alpha of the band area the cursor is located; the End key puts the cursor at the end of the line. The Tab key advances the cursor to the next tab stop.
The Admit key is mainly acclimated to about-face amid overtype mode, in which the cursor overwrites any argument that is present on and afterwards its accepted location, and admit mode, area the cursor inserts a appearance at its accepted position, banishment all characters accomplished it one position further. The Delete key discards the appearance advanced of the cursor's position, affective all afterward characters one position "back" appear the freed place. On abounding anthology computer keyboards the key labeled Delete (sometimes Delete and Backspace are printed on the aforementioned key) serves the aforementioned purpose as a Backspace key. The Backspace key deletes the above-mentioned character.
Lock keys lock allotment of a keyboard, depending on the settings selected. The lock keys are broadcast about the keyboard. A lot of styles of keyboards accept three LEDs advertence which locks are enabled, in the high appropriate bend aloft the numeric pad. The lock keys cover Annal lock, Num lock (which allows the use of the numeric keypad), and Caps lock.
System commands
The SysRq and Print awning commands generally allotment the aforementioned key. SysRq was acclimated in beforehand computers as a "panic" button to balance from crashes. The Print awning command acclimated to abduction the absolute awning and forward it to the printer, but in the present it usually puts a screenshot in the clipboard. The Breach key/Pause key no best has a categorical purpose. Its origins go aback to teleprinter users, who capital a key that would briefly arrest the communications line. The Breach key can be acclimated by software in several altered ways, such as to about-face amid assorted login sessions, to abolish a program, or to arrest a modem connection.
In programming, abnormally old DOS-style BASIC, Pascal and C, Breach is acclimated (in affiliation with Ctrl) to stop affairs execution. In accession to this, Linux and variants, as able-bodied as abounding DOS programs, amusement this aggregate the aforementioned as Ctrl+C. On avant-garde keyboards, the breach key is usually labeled Pause/Break. In a lot of Windows environments, the key aggregate Windows key+Pause brings up the adjustment properties.
The Escape key (often abbreviated Esc) is acclimated to admit an escape sequence. As a lot of computer users no best are anxious with the data of authoritative their computer's peripherals, the assignment for which the escape sequences were originally designed, the escape key was appointed by appliance programmers, a lot of generally to "escape" or aback out of a mistaken command. This use continues today in Microsoft Windows's use of escape as a adjustment in chat boxes for No, Quit, Exit, Cancel, or Abort.
A accepted appliance today of the Esc key is as a adjustment key for the Stop button in abounding web browsers. On machines active Microsoft Windows, above-mentioned to the accomplishing of the Windows key on keyboards, the archetypal convenance for invoking the "start" button was to authority down the ascendancy key and columnist escape. This action still works in Windows 2000, XP, Windows Vista and Windows 7.
The Card key or Appliance key is a key begin on Windows-oriented computer keyboards. It is acclimated to barrage a ambience card with the keyboard rather than with the accepted appropriate abrasion button. The key's attribute is a baby figure depicting a cursor aerial aloft a menu. This key was created at the aforementioned time as the Windows key. This key is commonly acclimated if the appropriate abrasion button is not present on the mouse. Some Windows accessible terminals do not accept a Card key on their keyboard to anticipate users from right-clicking (however, in abounding windows applications, a agnate functionality can be invoked with the Shift+F10 keyboard shortcut).
Miscellaneous
Multimedia buttons on some keyboards accord quick admission to the Internet or ascendancy the aggregate of the speakers.
Many, but not all, computer keyboards accept a numeric keypad to the appropriate of the alphabetic keyboard which contains numbers, basal algebraic symbols (e.g., addition, subtraction, etc.), and a few action keys. On Japanese/Korean keyboards, there may be Emphasis ascribe keys. Some keyboards accept adeptness administration keys (e.g., adeptness key, beddy-bye key and deathwatch key); Internet keys to admission a web browser or E-mail; and/or multimedia keys, such as aggregate controls or keys that can be programmed by the user to barrage a defined software or command like ablution a bold or abbreviate all windows.
Multiple layouts
It is accessible to install assorted keyboard layouts aural an operating adjustment and about-face amid them, either through appearance implemented aural the OS, or through an alien application. Microsoft Windows,8 Linux,9 and Mac10 accommodate abutment to add keyboard layouts and accept from them.
Layout alteration software
The appearance cipher produced by any key columnist is bent by the keyboard disciplinarian software. A key columnist generates a scancode which is interpreted as an alphanumeric appearance or ascendancy function. Depending on operating systems, assorted appliance programs are accessible to create, add and about-face a part of keyboard layouts. Abounding programs are available, some of which are emphasis specific.
The adjustment of symbols of specific emphasis can be customized. An absolute keyboard blueprint can be edited, and a new blueprint can be created application this blazon of software.
For example, Ukelele for Mac, The Microsoft Keyboard Blueprint Creator11 and open-source Avro Keyboard for Windows accommodate the adeptness to adapt the keyboard blueprint as desired. Added programs with agnate functions cover Avro Keyboard, Tavultesoft Keyman Developer,12 The Microsoft Keyboard Blueprint Creator,13 MountFocus Keyboard Designer,14 Map Keyboard, KbdEdit, Key Customizer, Keyboard Remapper, Infine Keyboard Commander for Windows; and X Neural Switcher, Keyboard Blueprint Editor15 and Keyboard Blueprint Creator16 for Linux.
Main article: Keyboard layout
The 104-key PC US English QWERTY keyboard blueprint acquired from the accepted typewriter keyboard, with added keys for computing.
The Dvorak Simplified Keyboard blueprint arranges keys so that frequently acclimated keys are easiest to press, which reduces beef fatigue if accounting accepted English.
There are a amount of altered arrange of alphabetic, numeric, and punctuation symbols on keys. These altered keyboard layouts appear mainly because altered humans charge simple admission to altered symbols, either because they are inputting argument in altered languages, or because they charge a specialized blueprint for mathematics, accounting, computer programming, or added purposes. The United States keyboard blueprint is acclimated as absence in the currently a lot of accepted operating systems: Windows,4 Mac OS X5 and Linux.67 The accepted QWERTY-based blueprint was advised aboriginal in the era of automated typewriters, so its ergonomics were compromised to acquiesce for the automated limitations of the typewriter.
As the letter-keys were absorbed to levers that bare to move freely, artist Christopher Sholes developed the QWERTY blueprint to abate the likelihood of jamming. With the appearance of computers, batten jams are no best an issue, but nevertheless, QWERTY layouts were adopted for cyberbanking keyboards because they were broadly used. Alternative layouts such as the Dvorak Simplified Keyboard are not in boundless use.
The QWERTZ blueprint is broadly acclimated in Germany and abundant of Central Europe. The capital aberration amid it and QWERTY is that Y and Z are swapped, and a lot of appropriate characters such as brackets are replaced by diacritical characters.
Another bearings takes abode with "national" layouts. Keyboards advised for accounting in Spanish accept some characters shifted, to absolution the amplitude for Г‘ Г±; similarly, those for French and added European languages may accept a appropriate key for the appearance Г‡ Г§. The AZERTY blueprint is acclimated in France, Belgium and some neighbouring countries. It differs from the QWERTY blueprint in that the A and Q are swapped, the Z and W are swapped, and the M is confused from the appropriate of N to the appropriate of L (where colon/semicolon is on a US keyboard). The digits 0 to 9 are on the aforementioned keys, but to be typed the about-face key accept to be pressed. The unshifted positions are acclimated for absolute characters.
Keyboards in abounding locations of Asia may accept appropriate keys to about-face amid the Latin appearance set and a absolutely altered accounting system. Japanese blueprint keyboards can be switched amid assorted Japanese ascribe methods and the Latin alphabet by signaling the operating system's ascribe analyst of the change, and some operating systems (namely the Windows family) adapt the appearance "" as "ВҐ" for affectation purposes afterwards alteration the bytecode which has led some keyboard makers to mark "" as "ВҐ" or both. In the Arab world, keyboards can generally be switched amid Arabic and Latin characters.
In bilingual regions of Canada and in the French-speaking arena of QuГ©bec, keyboards can generally be switched amid an English and a French-language keyboard; while both keyboards allotment the aforementioned QWERTY alphabetic layout, the French-language keyboard enables the user to blazon absolute vowels such as "Г©" or "Г " with a individual keystroke. Application keyboards for added languages leads to a conflict: the angel on the key does not accord to the character. In such cases, anniversary new emphasis may crave an added characterization on the keys, because the accepted keyboard layouts do not allotment even agnate characters of altered languages (see the archetype in the amount above).
Key types
Alphanumeric
A Hebrew keyboard lets the user blazon in both Hebrew and the Latin alphabet.
A Greek keyboard lets the user blazon in both Greek and the Latin alphabet (Macbook Pro).
The Ascendancy and Alt keys are important modifier keys.
A Space-cadet keyboard has abounding modifier keys.
Alphabetical, numeric, and punctuation keys are acclimated in the aforementioned appearance as a typewriter keyboard to admission their corresponding attribute into a chat processing program, argument editor, abstracts spreadsheet, or added program. Abounding of these keys will aftermath altered symbols if modifier keys or about-face keys are pressed. The alphabetic characters become uppercase if the about-face key or Caps Lock key is depressed. The numeric characters become symbols or punctuation marks if the about-face key is depressed. The alphabetical, numeric, and punctuation keys can aswell accept added functions if they are apprenticed at the aforementioned time as some modifier keys.
The Amplitude bar is a accumbent bar in the basal row, which is decidedly added than added keys. Like the alphanumeric characters, it is aswell descended from the automated typewriter. Its capital purpose is to admission the amplitude amid words during typing. It is ample abundant so that a deride from either duke can use it easily. Depending on the operating system, if the amplitude bar is acclimated with a modifier key such as the ascendancy key, it may accept functions such as resizing or closing the accepted window, half-spacing, or backspacing. In computer amateur and added applications the key has countless uses in accession to its accustomed purpose in typing, such as jumping and abacus marks to analysis boxes. In assertive programs for playback of agenda video, the amplitude bar is acclimated for pausing and resuming the playback.
Modifiers
Modifier keys are appropriate keys that adapt the accustomed activity of accession key, if the two are apprenticed in combination. For example, + in Microsoft Windows will abutting the affairs in an alive window. In contrast, acute just will apparently do nothing, unless assigned a specific action in a accurate program. By themselves, modifier keys usually do nothing.
The a lot of broadly acclimated modifier keys cover the Ascendancy key, About-face key and the Alt key. The AltGr key is acclimated to admission added symbols for keys that accept three symbols printed on them. On the Macintosh and Apple keyboards, the modifier keys are the Option key and Command key, respectively. On MIT computer keyboards, the Meta key is acclimated as a modifier and for Windows keyboards, there is a Windows key. Compact keyboard layouts generally use a Fn key. "Dead keys" acquiesce adjustment of a characteristic mark, such as an accent, on the afterward letter (e.g., the Compose key).
The Enter/Return key about causes a command line, window anatomy or chat box to accomplish its absence function, which is about to accomplishment an "entry" and activate the adapted process. In chat processing applications, acute the admission key ends a branch and starts a new one.
Navigation and accounting modes
Navigation keys cover a array of keys which move the cursor to altered positions on the screen. Arrow keys are programmed to move the cursor in a defined direction; page annal keys, such as the Page Up and Page Down keys, annal the page up and down. The Home key is acclimated to acknowledgment the cursor to the alpha of the band area the cursor is located; the End key puts the cursor at the end of the line. The Tab key advances the cursor to the next tab stop.
The Admit key is mainly acclimated to about-face amid overtype mode, in which the cursor overwrites any argument that is present on and afterwards its accepted location, and admit mode, area the cursor inserts a appearance at its accepted position, banishment all characters accomplished it one position further. The Delete key discards the appearance advanced of the cursor's position, affective all afterward characters one position "back" appear the freed place. On abounding anthology computer keyboards the key labeled Delete (sometimes Delete and Backspace are printed on the aforementioned key) serves the aforementioned purpose as a Backspace key. The Backspace key deletes the above-mentioned character.
Lock keys lock allotment of a keyboard, depending on the settings selected. The lock keys are broadcast about the keyboard. A lot of styles of keyboards accept three LEDs advertence which locks are enabled, in the high appropriate bend aloft the numeric pad. The lock keys cover Annal lock, Num lock (which allows the use of the numeric keypad), and Caps lock.
System commands
The SysRq and Print awning commands generally allotment the aforementioned key. SysRq was acclimated in beforehand computers as a "panic" button to balance from crashes. The Print awning command acclimated to abduction the absolute awning and forward it to the printer, but in the present it usually puts a screenshot in the clipboard. The Breach key/Pause key no best has a categorical purpose. Its origins go aback to teleprinter users, who capital a key that would briefly arrest the communications line. The Breach key can be acclimated by software in several altered ways, such as to about-face amid assorted login sessions, to abolish a program, or to arrest a modem connection.
In programming, abnormally old DOS-style BASIC, Pascal and C, Breach is acclimated (in affiliation with Ctrl) to stop affairs execution. In accession to this, Linux and variants, as able-bodied as abounding DOS programs, amusement this aggregate the aforementioned as Ctrl+C. On avant-garde keyboards, the breach key is usually labeled Pause/Break. In a lot of Windows environments, the key aggregate Windows key+Pause brings up the adjustment properties.
The Escape key (often abbreviated Esc) is acclimated to admit an escape sequence. As a lot of computer users no best are anxious with the data of authoritative their computer's peripherals, the assignment for which the escape sequences were originally designed, the escape key was appointed by appliance programmers, a lot of generally to "escape" or aback out of a mistaken command. This use continues today in Microsoft Windows's use of escape as a adjustment in chat boxes for No, Quit, Exit, Cancel, or Abort.
A accepted appliance today of the Esc key is as a adjustment key for the Stop button in abounding web browsers. On machines active Microsoft Windows, above-mentioned to the accomplishing of the Windows key on keyboards, the archetypal convenance for invoking the "start" button was to authority down the ascendancy key and columnist escape. This action still works in Windows 2000, XP, Windows Vista and Windows 7.
The Card key or Appliance key is a key begin on Windows-oriented computer keyboards. It is acclimated to barrage a ambience card with the keyboard rather than with the accepted appropriate abrasion button. The key's attribute is a baby figure depicting a cursor aerial aloft a menu. This key was created at the aforementioned time as the Windows key. This key is commonly acclimated if the appropriate abrasion button is not present on the mouse. Some Windows accessible terminals do not accept a Card key on their keyboard to anticipate users from right-clicking (however, in abounding windows applications, a agnate functionality can be invoked with the Shift+F10 keyboard shortcut).
Miscellaneous
Multimedia buttons on some keyboards accord quick admission to the Internet or ascendancy the aggregate of the speakers.
Many, but not all, computer keyboards accept a numeric keypad to the appropriate of the alphabetic keyboard which contains numbers, basal algebraic symbols (e.g., addition, subtraction, etc.), and a few action keys. On Japanese/Korean keyboards, there may be Emphasis ascribe keys. Some keyboards accept adeptness administration keys (e.g., adeptness key, beddy-bye key and deathwatch key); Internet keys to admission a web browser or E-mail; and/or multimedia keys, such as aggregate controls or keys that can be programmed by the user to barrage a defined software or command like ablution a bold or abbreviate all windows.
Multiple layouts
It is accessible to install assorted keyboard layouts aural an operating adjustment and about-face amid them, either through appearance implemented aural the OS, or through an alien application. Microsoft Windows,8 Linux,9 and Mac10 accommodate abutment to add keyboard layouts and accept from them.
Layout alteration software
The appearance cipher produced by any key columnist is bent by the keyboard disciplinarian software. A key columnist generates a scancode which is interpreted as an alphanumeric appearance or ascendancy function. Depending on operating systems, assorted appliance programs are accessible to create, add and about-face a part of keyboard layouts. Abounding programs are available, some of which are emphasis specific.
The adjustment of symbols of specific emphasis can be customized. An absolute keyboard blueprint can be edited, and a new blueprint can be created application this blazon of software.
For example, Ukelele for Mac, The Microsoft Keyboard Blueprint Creator11 and open-source Avro Keyboard for Windows accommodate the adeptness to adapt the keyboard blueprint as desired. Added programs with agnate functions cover Avro Keyboard, Tavultesoft Keyman Developer,12 The Microsoft Keyboard Blueprint Creator,13 MountFocus Keyboard Designer,14 Map Keyboard, KbdEdit, Key Customizer, Keyboard Remapper, Infine Keyboard Commander for Windows; and X Neural Switcher, Keyboard Blueprint Editor15 and Keyboard Blueprint Creator16 for Linux.
Illumination
Keyboards and keypads may be aflame from inside, abnormally on accessories for adaptable use. Illumination facilitates the use of the keyboard or keypad in aphotic environments. Some gaming keyboards accept afire keys, to accomplish it easier for gamers to acquisition command keys while arena in a aphotic room. Some computers may accept baby LED lights in a few important action keys, to admonish users that the action is activated (see photo).
Technology
Key switches
In the aboriginal cyberbanking keyboards in the aboriginal 1970s, the key switches were alone switches amid into holes in metal frames. These keyboards amount from 80–120 US dollars and were acclimated in mainframe abstracts terminals. The a lot of accustomed about-face types were reed switches (contacts amid in a exhaustion in a bottle capsule, afflicted by a allurement army on the about-face plunger – from Clare-Pendar17 in Post Falls Idaho, which became allotment of General Instrument, which acclimated reedswitch capsules fabricated by C.P. Clare Co.18 in Illinois; and Key Tronic Corporation of Spokane, Washington), Hall-effect switches (using a Hall-effect semiconductor breadth a accustomed is generated by a casual allurement – from Microswitch19 in Illinois, which became allotment of Honeywell), and anterior amount switches (again, activated by a allurement – from Cortron,20 which was allotment of ITW/Illinois Tool Works). These switches were rated to endure for 100 actor cycles and had 0.187-inch (4.75 mm) key travel, compared to 0.110 inch (2.79 mm) today.
In the mid 1970s, lower-cost direct-contact key switches were introduced, but their activity in about-face cycles was abundant beneath (rated ten actor cycles) because they were accessible to the environment. This became added acceptable, however, for use in computer terminals at the time, which began to see added beneath archetypal lifespans as they advanced.
In 1978, Key Tronic Corporation alien keyboards with capacitive-based switches, one of the aboriginal keyboard technologies to not use absolute switches. There was artlessly a blot pad with a conductive-coated Mylar bogus breadth on the about-face plunger, and two arch trace patterns on the printed ambit lath below. As the key was depressed, the capacitance amid the plunger pad and the patterns on the PCB beneath changed, which was detected by chip circuits (IC). These keyboards were claimed to accept the aforementioned believability as the added "solid-state switch" keyboards such as anterior and Hall-Effect, but aggressive with direct-contact keyboards. Prices of $60 for keyboards were accomplished and Key Tronic rapidly became the better absolute keyboard manufacturer.
Meanwhile, IBM fabricated their own keyboards, appliance their own patented technology: Keys on earlier IBM keyboards were fabricated with a "buckling spring" mechanism, in which a braid animation beneath the key buckles beneath burden from the user's finger, triggering a bang that presses two bogus bedding (membranes) with conductive traces together, commutual a circuit. This produces a beat sound, and gives concrete acknowledgment for the typist advertence that the key has been depressed.2122
The aboriginal cyberbanking keyboards had a typewriter key biking ambit of 0.187 inches (4.75 mm), keytops were a half-inch (12.7 mm) high, and keyboards were about two inches (5 cm) thick. Over time, beneath key biking was accustomed in the market, assuredly landing on 0.110 inches (2.79 mm). Coincident with this, Key Tronic was the aboriginal aggregation to acquaint a keyboard which was alone about one inch thick. And now keyboards admeasurement alone about a half-inch thick.
Keytops are an important aspect of keyboards. In the beginning, keyboard keytops had a "dish shape" on top, like typewriters afore them. Keyboard key legends accept to be acutely abiding over tens of millions of depressions, back they are subjected to acute automated abrasion from fingers and fingernails, and accountable to duke oils and creams, so block and bushing key legends with paint, as was done ahead for alone switches, was never acceptable. So, for the aboriginal cyberbanking keyboards, the key legends were produced by two-shot (or double-shot, or two-color) molding, breadth either the key carapace or the central of the key with the key fable was molded first, and again the added blush molded second. But, to save cost, added methods were explored, such as sublimation press and laser engraving, both methods which could be acclimated to book a accomplished keyboard at the aforementioned time.
Initially, sublimation printing, breadth a appropriate ink is printed assimilate the keycap apparent and the appliance of calefaction causes the ink molecules to access and amalgamate with the bogus modules, had a botheration because feel oils acquired the molecules to disperse, but again a necessarily actual harder bright blanket was activated to anticipate this. Coincident with sublimation printing, which was aboriginal acclimated in top aggregate by IBM on their keyboards, was the addition by IBM of single-curved-dish keycaps to facilitate superior press of key legends by accepting a consistently arced apparent instead of a dish. But one botheration with sublimation or laser press was that the processes took too continued and alone aphotic legends could be printed on light-colored keys. On addition note, IBM was altered in appliance abstracted shells, or "keycaps", on keytop bases.This ability accept fabricated their accomplishment of altered keyboard layouts added flexible, but the acumen for accomplishing this was that the bogus actual that bare to be acclimated for sublimation press was altered from accepted ABS keytop bogus material.
Three final automated technologies brought keyboards to breadth they are today, active the amount able-bodied beneath $10:
"Monoblock" keyboard designs were developed breadth alone about-face housings were alone and a jumpsuit "monoblock" apartment acclimated instead. This was accessible because of abstraction techniques that could accommodate actual bound tolerances for the switch-plunger holes and guides beyond the amplitude of the keyboard so that the key plunger-to-housing clearances were not too bound or too loose, either of which could could cause the keys to bind.
The use of contact-switch film bedding beneath the monoblock. This technology came from flat-panel about-face membranes, breadth the about-face contacts are printed central of a top and basal layer, with a spacer band in between, so that if burden is activated to the breadth above, a absolute electrical acquaintance is made. The film layers can be printed by very-high volume, bargain "reel-to-reel" press machines, with anniversary keyboard film cut and punched out afterwards.
The use of pad-printed keytops (called "Tampo printed" at the time because Tampo23 was the a lot of accustomed accessories manufacturer). Initially sublimation ink was acclimated (see above), but actual abiding clear-coats are now printed over the key legends to assure them. These coatings are aswell acclimated to abate glare, and in abounding cases accept an anti-microbial agreeable added for user protection.24
Plastic abstracts played a actual important allotment in the development and advance of cyberbanking keyboards. Until "monoblocks" came along, GE's "self-lubricating" Delrin was the alone bogus actual for keyboard about-face plungers that could bear the assault over tens of millions of cycles of lifetime use. Greasing or oiling about-face plungers was abominable because it would allure clay over time which would eventually affect the feel and even bind the key switches (although keyboard manufacturers would sometimes bastard this into their keyboards, abnormally if they could not ascendancy the tolerances of the key plungers and housings able-bodied abundant to accept a bland key abasement feel or anticipate binding). But Delrin was alone accessible in atramentous and white, and was not acceptable for keytops (too soft), so keytops use ABS plastic. However, as bogus abstraction avant-garde in advancement bound tolerances, and as key biking breadth bargain from 0.187-inch to 0.110-inch (4.75 mm to 2.79 mm), single-part keytop/plungers could be fabricated of ABS, with the keyboard monolocks aswell fabricated of ABS.
Control processor
Computer keyboards cover ascendancy chip to catechumen key presses into key codes (usually scancodes) that the computer's electronics can understand. The key switches are affiliated via the printed ambit lath in an electrical X-Y cast breadth a voltage is provided sequentially to the Y curve and, if a key is depressed, detected sequentially by scanning the X lines.
The aboriginal computer keyboards were for mainframe computer abstracts terminals and acclimated alone cyberbanking parts. The aboriginal keyboard chip was alien in 1972 by General Instruments, but keyboards accept been appliance the single-chip 8048 microcontroller alternative back it became accessible in 1978. The keyboard about-face cast is active to its inputs, it converts the keystrokes to key codes, and, for a alone keyboard, sends the codes down a consecutive cable (the keyboard cord) to the capital processor on the computer motherboard. This consecutive keyboard cable advice is alone bi-directional to the admeasurement that the computer's electronics controls the beam of the caps lock, num lock and annal lock lights.
One analysis for whether the computer has comatose is acute the caps lock key. The keyboard sends the key cipher to the keyboard disciplinarian active in the capital computer; if the capital computer is operating, it commands the ablaze to about-face on. All the added indicator lights plan in a agnate way. The keyboard disciplinarian aswell advance the Shift, alt and ascendancy accompaniment of the keyboard.
Some lower-quality keyboards accept assorted or apocryphal key entries due to bare electrical designs. These are acquired by bare keyswitch "debouncing" or bare keyswitch cast blueprint that don't acquiesce assorted keys to be depressed at the aforementioned time, both affairs which are explained below:
When acute a keyboard key, the key contacts may "bounce" adjoin anniversary added for several milliseconds afore they achieve into close contact. If released, they animation some added until they backslide to the uncontacted state. If the computer were watching for anniversary pulse, it would see abounding keystrokes for what the user anticipation was just one. To boldness this problem, the processor in a keyboard (or computer) "debounces" the keystrokes, by accumulation them beyond time to aftermath one "confirmed" keystroke.
Some low-quality keyboards aswell ache problems with rollover (that is, if assorted keys apprenticed at the aforementioned time, or if keys are apprenticed so fast that assorted keys are down aural the aforementioned milliseconds). Aboriginal "solid-state" keyswitch keyboards did not accept this botheration because the keyswitches are electrically abandoned from anniversary other, and aboriginal "direct-contact" keyswitch keyboards abhorred this botheration by accepting abreast diodes for every keyswitch. These aboriginal keyboards had "n-key" rollover, which agency any amount of keys can be depressed and the keyboard will still admit the next key depressed. But if three keys are apprenticed (electrically closed) at the aforementioned time in a "direct contact" keyswitch cast that doesn't accept abreast diodes, the keyboard electronics can see a fourth "phantom" key which is the circle of the X and Y curve of the three keys. Some types of keyboard chip will annals a best amount of keys at one time. "Three-key" rollover, aswell alleged "phantom key blocking" or "phantom key lockout", will alone annals three keys and avoid all others until one of the three keys is lifted. This is undesirable, abnormally for fast accounting (hitting new keys afore the fingers can absolution antecedent keys), and amateur (designed for assorted key presses).
As direct-contact film keyboards became popular, the accessible rollover of keys was optimized by allegory the a lot of accepted key sequences and agreement these keys so that they do not potentially aftermath apparition keys in the electrical key cast (for example, artlessly agreement three or four keys that ability be depressed accompanying on the aforementioned X or aforementioned Y line, so that a apparition key intersection/short cannot happen), so that blocking a third key usually isn't a problem. But lower-quality keyboard designs and apprenticed engineers may not apperceive these tricks, and it can still be a botheration in amateur due to berserk altered or configurable layouts in altered games.
Connection types
There are several means of abutting a keyboard to a arrangement assemblage (more precisely, to its keyboard controller) appliance cables, including the accepted AT adapter frequently begin on motherboards, which was eventually replaced by the PS/2 and the USB connection. Prior to the iMac band of systems, Apple acclimated the proprietary Apple Desktop Bus for its keyboard connector.
Wireless keyboards accept become accustomed for their added user freedom. A wireless keyboard generally includes a appropriate aggregate transmitter and receiver assemblage that attaches to the computer's keyboard port. The wireless aspect is accomplished either by radio abundance (RF) or by bittersweet (IR) signals beatific and accustomed from both the keyboard and the assemblage absorbed to the computer. A wireless keyboard may use an industry accepted RF, alleged Bluetooth. With Bluetooth, the transceiver may be congenital into the computer. However, a wireless keyboard needs batteries to plan and may affectation a aegis botheration due to the accident of abstracts "eavesdropping" by hackers. Wireless solar keyboards allegation their batteries from baby solar panels appliance sunlight or accepted bogus lighting. An aboriginal archetype of a customer wireless keyboard is that of the Olivetti Envision.
In the aboriginal cyberbanking keyboards in the aboriginal 1970s, the key switches were alone switches amid into holes in metal frames. These keyboards amount from 80–120 US dollars and were acclimated in mainframe abstracts terminals. The a lot of accustomed about-face types were reed switches (contacts amid in a exhaustion in a bottle capsule, afflicted by a allurement army on the about-face plunger – from Clare-Pendar17 in Post Falls Idaho, which became allotment of General Instrument, which acclimated reedswitch capsules fabricated by C.P. Clare Co.18 in Illinois; and Key Tronic Corporation of Spokane, Washington), Hall-effect switches (using a Hall-effect semiconductor breadth a accustomed is generated by a casual allurement – from Microswitch19 in Illinois, which became allotment of Honeywell), and anterior amount switches (again, activated by a allurement – from Cortron,20 which was allotment of ITW/Illinois Tool Works). These switches were rated to endure for 100 actor cycles and had 0.187-inch (4.75 mm) key travel, compared to 0.110 inch (2.79 mm) today.
In the mid 1970s, lower-cost direct-contact key switches were introduced, but their activity in about-face cycles was abundant beneath (rated ten actor cycles) because they were accessible to the environment. This became added acceptable, however, for use in computer terminals at the time, which began to see added beneath archetypal lifespans as they advanced.
In 1978, Key Tronic Corporation alien keyboards with capacitive-based switches, one of the aboriginal keyboard technologies to not use absolute switches. There was artlessly a blot pad with a conductive-coated Mylar bogus breadth on the about-face plunger, and two arch trace patterns on the printed ambit lath below. As the key was depressed, the capacitance amid the plunger pad and the patterns on the PCB beneath changed, which was detected by chip circuits (IC). These keyboards were claimed to accept the aforementioned believability as the added "solid-state switch" keyboards such as anterior and Hall-Effect, but aggressive with direct-contact keyboards. Prices of $60 for keyboards were accomplished and Key Tronic rapidly became the better absolute keyboard manufacturer.
Meanwhile, IBM fabricated their own keyboards, appliance their own patented technology: Keys on earlier IBM keyboards were fabricated with a "buckling spring" mechanism, in which a braid animation beneath the key buckles beneath burden from the user's finger, triggering a bang that presses two bogus bedding (membranes) with conductive traces together, commutual a circuit. This produces a beat sound, and gives concrete acknowledgment for the typist advertence that the key has been depressed.2122
The aboriginal cyberbanking keyboards had a typewriter key biking ambit of 0.187 inches (4.75 mm), keytops were a half-inch (12.7 mm) high, and keyboards were about two inches (5 cm) thick. Over time, beneath key biking was accustomed in the market, assuredly landing on 0.110 inches (2.79 mm). Coincident with this, Key Tronic was the aboriginal aggregation to acquaint a keyboard which was alone about one inch thick. And now keyboards admeasurement alone about a half-inch thick.
Keytops are an important aspect of keyboards. In the beginning, keyboard keytops had a "dish shape" on top, like typewriters afore them. Keyboard key legends accept to be acutely abiding over tens of millions of depressions, back they are subjected to acute automated abrasion from fingers and fingernails, and accountable to duke oils and creams, so block and bushing key legends with paint, as was done ahead for alone switches, was never acceptable. So, for the aboriginal cyberbanking keyboards, the key legends were produced by two-shot (or double-shot, or two-color) molding, breadth either the key carapace or the central of the key with the key fable was molded first, and again the added blush molded second. But, to save cost, added methods were explored, such as sublimation press and laser engraving, both methods which could be acclimated to book a accomplished keyboard at the aforementioned time.
Initially, sublimation printing, breadth a appropriate ink is printed assimilate the keycap apparent and the appliance of calefaction causes the ink molecules to access and amalgamate with the bogus modules, had a botheration because feel oils acquired the molecules to disperse, but again a necessarily actual harder bright blanket was activated to anticipate this. Coincident with sublimation printing, which was aboriginal acclimated in top aggregate by IBM on their keyboards, was the addition by IBM of single-curved-dish keycaps to facilitate superior press of key legends by accepting a consistently arced apparent instead of a dish. But one botheration with sublimation or laser press was that the processes took too continued and alone aphotic legends could be printed on light-colored keys. On addition note, IBM was altered in appliance abstracted shells, or "keycaps", on keytop bases.This ability accept fabricated their accomplishment of altered keyboard layouts added flexible, but the acumen for accomplishing this was that the bogus actual that bare to be acclimated for sublimation press was altered from accepted ABS keytop bogus material.
Three final automated technologies brought keyboards to breadth they are today, active the amount able-bodied beneath $10:
"Monoblock" keyboard designs were developed breadth alone about-face housings were alone and a jumpsuit "monoblock" apartment acclimated instead. This was accessible because of abstraction techniques that could accommodate actual bound tolerances for the switch-plunger holes and guides beyond the amplitude of the keyboard so that the key plunger-to-housing clearances were not too bound or too loose, either of which could could cause the keys to bind.
The use of contact-switch film bedding beneath the monoblock. This technology came from flat-panel about-face membranes, breadth the about-face contacts are printed central of a top and basal layer, with a spacer band in between, so that if burden is activated to the breadth above, a absolute electrical acquaintance is made. The film layers can be printed by very-high volume, bargain "reel-to-reel" press machines, with anniversary keyboard film cut and punched out afterwards.
The use of pad-printed keytops (called "Tampo printed" at the time because Tampo23 was the a lot of accustomed accessories manufacturer). Initially sublimation ink was acclimated (see above), but actual abiding clear-coats are now printed over the key legends to assure them. These coatings are aswell acclimated to abate glare, and in abounding cases accept an anti-microbial agreeable added for user protection.24
Plastic abstracts played a actual important allotment in the development and advance of cyberbanking keyboards. Until "monoblocks" came along, GE's "self-lubricating" Delrin was the alone bogus actual for keyboard about-face plungers that could bear the assault over tens of millions of cycles of lifetime use. Greasing or oiling about-face plungers was abominable because it would allure clay over time which would eventually affect the feel and even bind the key switches (although keyboard manufacturers would sometimes bastard this into their keyboards, abnormally if they could not ascendancy the tolerances of the key plungers and housings able-bodied abundant to accept a bland key abasement feel or anticipate binding). But Delrin was alone accessible in atramentous and white, and was not acceptable for keytops (too soft), so keytops use ABS plastic. However, as bogus abstraction avant-garde in advancement bound tolerances, and as key biking breadth bargain from 0.187-inch to 0.110-inch (4.75 mm to 2.79 mm), single-part keytop/plungers could be fabricated of ABS, with the keyboard monolocks aswell fabricated of ABS.
Control processor
Computer keyboards cover ascendancy chip to catechumen key presses into key codes (usually scancodes) that the computer's electronics can understand. The key switches are affiliated via the printed ambit lath in an electrical X-Y cast breadth a voltage is provided sequentially to the Y curve and, if a key is depressed, detected sequentially by scanning the X lines.
The aboriginal computer keyboards were for mainframe computer abstracts terminals and acclimated alone cyberbanking parts. The aboriginal keyboard chip was alien in 1972 by General Instruments, but keyboards accept been appliance the single-chip 8048 microcontroller alternative back it became accessible in 1978. The keyboard about-face cast is active to its inputs, it converts the keystrokes to key codes, and, for a alone keyboard, sends the codes down a consecutive cable (the keyboard cord) to the capital processor on the computer motherboard. This consecutive keyboard cable advice is alone bi-directional to the admeasurement that the computer's electronics controls the beam of the caps lock, num lock and annal lock lights.
One analysis for whether the computer has comatose is acute the caps lock key. The keyboard sends the key cipher to the keyboard disciplinarian active in the capital computer; if the capital computer is operating, it commands the ablaze to about-face on. All the added indicator lights plan in a agnate way. The keyboard disciplinarian aswell advance the Shift, alt and ascendancy accompaniment of the keyboard.
Some lower-quality keyboards accept assorted or apocryphal key entries due to bare electrical designs. These are acquired by bare keyswitch "debouncing" or bare keyswitch cast blueprint that don't acquiesce assorted keys to be depressed at the aforementioned time, both affairs which are explained below:
When acute a keyboard key, the key contacts may "bounce" adjoin anniversary added for several milliseconds afore they achieve into close contact. If released, they animation some added until they backslide to the uncontacted state. If the computer were watching for anniversary pulse, it would see abounding keystrokes for what the user anticipation was just one. To boldness this problem, the processor in a keyboard (or computer) "debounces" the keystrokes, by accumulation them beyond time to aftermath one "confirmed" keystroke.
Some low-quality keyboards aswell ache problems with rollover (that is, if assorted keys apprenticed at the aforementioned time, or if keys are apprenticed so fast that assorted keys are down aural the aforementioned milliseconds). Aboriginal "solid-state" keyswitch keyboards did not accept this botheration because the keyswitches are electrically abandoned from anniversary other, and aboriginal "direct-contact" keyswitch keyboards abhorred this botheration by accepting abreast diodes for every keyswitch. These aboriginal keyboards had "n-key" rollover, which agency any amount of keys can be depressed and the keyboard will still admit the next key depressed. But if three keys are apprenticed (electrically closed) at the aforementioned time in a "direct contact" keyswitch cast that doesn't accept abreast diodes, the keyboard electronics can see a fourth "phantom" key which is the circle of the X and Y curve of the three keys. Some types of keyboard chip will annals a best amount of keys at one time. "Three-key" rollover, aswell alleged "phantom key blocking" or "phantom key lockout", will alone annals three keys and avoid all others until one of the three keys is lifted. This is undesirable, abnormally for fast accounting (hitting new keys afore the fingers can absolution antecedent keys), and amateur (designed for assorted key presses).
As direct-contact film keyboards became popular, the accessible rollover of keys was optimized by allegory the a lot of accepted key sequences and agreement these keys so that they do not potentially aftermath apparition keys in the electrical key cast (for example, artlessly agreement three or four keys that ability be depressed accompanying on the aforementioned X or aforementioned Y line, so that a apparition key intersection/short cannot happen), so that blocking a third key usually isn't a problem. But lower-quality keyboard designs and apprenticed engineers may not apperceive these tricks, and it can still be a botheration in amateur due to berserk altered or configurable layouts in altered games.
Connection types
There are several means of abutting a keyboard to a arrangement assemblage (more precisely, to its keyboard controller) appliance cables, including the accepted AT adapter frequently begin on motherboards, which was eventually replaced by the PS/2 and the USB connection. Prior to the iMac band of systems, Apple acclimated the proprietary Apple Desktop Bus for its keyboard connector.
Wireless keyboards accept become accustomed for their added user freedom. A wireless keyboard generally includes a appropriate aggregate transmitter and receiver assemblage that attaches to the computer's keyboard port. The wireless aspect is accomplished either by radio abundance (RF) or by bittersweet (IR) signals beatific and accustomed from both the keyboard and the assemblage absorbed to the computer. A wireless keyboard may use an industry accepted RF, alleged Bluetooth. With Bluetooth, the transceiver may be congenital into the computer. However, a wireless keyboard needs batteries to plan and may affectation a aegis botheration due to the accident of abstracts "eavesdropping" by hackers. Wireless solar keyboards allegation their batteries from baby solar panels appliance sunlight or accepted bogus lighting. An aboriginal archetype of a customer wireless keyboard is that of the Olivetti Envision.
Alternative text-entering methods
Optical appearance acceptance (OCR) is bigger to rekeying for converting absolute argument that is already accounting down but not in machine-readable architecture (for example, a Linotype-composed book from the 1940s). In added words, to catechumen the argument from an angel to editable argument (that is, a cord of appearance codes), a being could re-type it, or a computer could attending at the angel and deduce what anniversary appearance is. OCR technology has already accomplished an absorbing accompaniment (for example, Google Book Search) and promises added for the future.
Speech acceptance converts accent into machine-readable argument (that is, a cord of appearance codes). This technology has aswell accomplished an avant-garde accompaniment and is implemented in assorted software products. For assertive uses (e.g., archetype of medical or acknowledged dictation; journalism; autograph essays or novels) it is starting to alter the keyboard; however, it does not abuse to alter keyboards absolutely anytime soon. It can, however, adapt commands (for example, "close window" or "undo word") in accession to text. Therefore, it has abstract abeyant to alter keyboards absolutely (whereas OCR replaces them alone for a assertive affectionate of task).
Pointing accessories can be acclimated to admission argument or characters in contexts area application a concrete keyboard would be inappropriate or impossible. These accessories about present characters on a display, in a blueprint that provides fast admission to the added frequently acclimated characters or appearance combinations. Popular examples of this affectionate of ascribe are Graffiti, Dasher and on-screen basic keyboards.
Speech acceptance converts accent into machine-readable argument (that is, a cord of appearance codes). This technology has aswell accomplished an avant-garde accompaniment and is implemented in assorted software products. For assertive uses (e.g., archetype of medical or acknowledged dictation; journalism; autograph essays or novels) it is starting to alter the keyboard; however, it does not abuse to alter keyboards absolutely anytime soon. It can, however, adapt commands (for example, "close window" or "undo word") in accession to text. Therefore, it has abstract abeyant to alter keyboards absolutely (whereas OCR replaces them alone for a assertive affectionate of task).
Pointing accessories can be acclimated to admission argument or characters in contexts area application a concrete keyboard would be inappropriate or impossible. These accessories about present characters on a display, in a blueprint that provides fast admission to the added frequently acclimated characters or appearance combinations. Popular examples of this affectionate of ascribe are Graffiti, Dasher and on-screen basic keyboards.
Other issues
Keystroke logging
Keystroke logging (often called keylogging) is a method of capturing and recording user keystrokes. While it is used legally to measure employee productivity on certain clerical tasks, or by law enforcement agencies to find out about illegal activities, it is also used by hackers for various illegal or malicious acts. Hackers use keyloggers as a means to obtain passwords or encryption keys and thus bypass other security measures.
Keystroke logging can be achieved by both hardware and software means. Hardware key loggers are attached to the keyboard cable or installed inside standard keyboards. Software keyloggers work on the target computer's operating system and gain unauthorized access to the hardware, hook into the keyboard with functions provided by the OS, or use remote access software to transmit recorded data out of the target computer to a remote location. Some hackers also use wireless keylogger sniffers to collect packets of data being transferred from a wireless keyboard and its receiver, and then they crack the encryption key being used to secure wireless communications between the two devices.
Anti-spyware applications are able to detect many keyloggers and cleanse them. Responsible vendors of monitoring software support detection by anti-spyware programs, thus preventing abuse of the software. Enabling a firewall does not stop keyloggers per se, but can possibly prevent transmission of the logged material over the net if properly configured. Network monitors (also known as reverse-firewalls) can be used to alert the user whenever an application attempts to make a network connection. This gives the user the chance to prevent the keylogger from "phoning home" with his or her typed information. Automatic form-filling programs can prevent keylogging entirely by not using the keyboard at all. Most keyloggers can be fooled by alternating between typing the login credentials and typing characters somewhere else in the focus window.25
Wireless keystroke logging
Also known as remote keylogging or wireless keylogging.
In their research, "Compromising Electromagnetic Emanations of Wired Keyboard",26 Vuagnoux and Pasini have provided evidence that modern keyboards radiate compromising electromagnetic emanations. The four techniques presented in their paper prove that these basic devices are generally not sufficiently protected against compromising emanations. Additionally, they showed that these emanations can be captured with relatively inexpensive equipment and keystrokes are recovered27 not only in the semi-anechoic chamber but in practical environments as well (e.g. office). The consequences of these attacks are that compromising electromagnetic emanations of keyboards still represent a security risk. PS/2, USB, laptop and wireless keyboards are vulnerable. Moreover, there is no software patch to avoid these attacks. Hardware has to be replaced to obtain safe devices. Due to cost pressure in the design and lack of knowledge, manufacturers do not systematically protect keyboards. Even in the practical space of an office with multiple keyboards, Vuagnoux and Pasini were able to deduce a specific fingerprint for every keyboard. When multiple keyboards are radiating at the same time, they are able to identify and differentiate them.
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.28
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 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 can lessen the repetitive strain on the arms and hands.
Bacteria
A growing body of research raises the question if keyboards can be a health hazard. Some keyboards were found to contain five times more germs than a toilet seat.29 Dr. Aaron Glatt, spokesperson for the Infectious Disease Society of America, remembers that "there is no surface under the sun ... that is sterile" and "there is overwhelming evidence that this is not a danger for most people." Basic hygiene measures like handwashing and not sharing the keyboard may reduce exposure to harmful bacteria.
Keystroke logging (often called keylogging) is a method of capturing and recording user keystrokes. While it is used legally to measure employee productivity on certain clerical tasks, or by law enforcement agencies to find out about illegal activities, it is also used by hackers for various illegal or malicious acts. Hackers use keyloggers as a means to obtain passwords or encryption keys and thus bypass other security measures.
Keystroke logging can be achieved by both hardware and software means. Hardware key loggers are attached to the keyboard cable or installed inside standard keyboards. Software keyloggers work on the target computer's operating system and gain unauthorized access to the hardware, hook into the keyboard with functions provided by the OS, or use remote access software to transmit recorded data out of the target computer to a remote location. Some hackers also use wireless keylogger sniffers to collect packets of data being transferred from a wireless keyboard and its receiver, and then they crack the encryption key being used to secure wireless communications between the two devices.
Anti-spyware applications are able to detect many keyloggers and cleanse them. Responsible vendors of monitoring software support detection by anti-spyware programs, thus preventing abuse of the software. Enabling a firewall does not stop keyloggers per se, but can possibly prevent transmission of the logged material over the net if properly configured. Network monitors (also known as reverse-firewalls) can be used to alert the user whenever an application attempts to make a network connection. This gives the user the chance to prevent the keylogger from "phoning home" with his or her typed information. Automatic form-filling programs can prevent keylogging entirely by not using the keyboard at all. Most keyloggers can be fooled by alternating between typing the login credentials and typing characters somewhere else in the focus window.25
Wireless keystroke logging
Also known as remote keylogging or wireless keylogging.
In their research, "Compromising Electromagnetic Emanations of Wired Keyboard",26 Vuagnoux and Pasini have provided evidence that modern keyboards radiate compromising electromagnetic emanations. The four techniques presented in their paper prove that these basic devices are generally not sufficiently protected against compromising emanations. Additionally, they showed that these emanations can be captured with relatively inexpensive equipment and keystrokes are recovered27 not only in the semi-anechoic chamber but in practical environments as well (e.g. office). The consequences of these attacks are that compromising electromagnetic emanations of keyboards still represent a security risk. PS/2, USB, laptop and wireless keyboards are vulnerable. Moreover, there is no software patch to avoid these attacks. Hardware has to be replaced to obtain safe devices. Due to cost pressure in the design and lack of knowledge, manufacturers do not systematically protect keyboards. Even in the practical space of an office with multiple keyboards, Vuagnoux and Pasini were able to deduce a specific fingerprint for every keyboard. When multiple keyboards are radiating at the same time, they are able to identify and differentiate them.
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.28
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 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 can lessen the repetitive strain on the arms and hands.
Bacteria
A growing body of research raises the question if keyboards can be a health hazard. Some keyboards were found to contain five times more germs than a toilet seat.29 Dr. Aaron Glatt, spokesperson for the Infectious Disease Society of America, remembers that "there is no surface under the sun ... that is sterile" and "there is overwhelming evidence that this is not a danger for most people." Basic hygiene measures like handwashing and not sharing the keyboard may reduce exposure to harmful bacteria.
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