computer keyboard not to be confused with keyboard computer play media typing on a computer keyboard backlit keyboard lenovos thinkpad compact keyboard in computing a computer keyboard is a typewriterstyle device 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 teleprinterstyle keyboards became the main input method for computers keyboard keys buttons typically have characters engraved or printed on them while most keyboard keys produce letters numbers or signs characters other keys or simultaneous key presses can produce actions or execute computer commands in normal usage the keyboard is used as a text entry interface for typing text and numbers into a word processor text editor or any 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 key and reports all key presses to the controlling software keyboards are also used for computer gaming either regular keyboards or 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 controlaltdelete combination although on prewindows 95 microsoft operating systems this forced a reboot now it brings up a system security options screen a commandline interface is a type of user interface navigated entirely using a keyboard or some other similar device that does the job of one history while typewriters are the definitive ancestor of all keybased 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 as early as the 1870s teleprinterlike 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 1907 to 1910 by american mechanical engineer charles krum and his son howard with early contributions by electrical engineer frank pearne earlier 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 the keyboard on the teleprinter played a strong role in pointtopoint and pointtomultipoint 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 paperbased output device while the binac computer also made use of an electromechanically controlled typewriter for both data entry onto magnetic tape instead of paper and data output the 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 textonly user interfaces with sparse graphics gave way to comparatively graphicsrich icons on screen however keyboards remain central to humancomputer interaction to the present even as mobile personal computing devices such as smartphones and tablets adapt the keyboard as an optional virtual touchscreenbased means of data entry keyboard types one factor determining the size of a keyboard is the presence of duplicate keys such as a separate numeric keyboard or two each of shift alt and ctl for convenience further 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 or multiple pressing of a single key a keyboard with few keys is called a keypad another factor determining the size of a keyboard is the size and spacing of the keys 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 standard standard alphanumeric keyboards have keys that are on threequarter inch centers 0750inches 1905mm and have a key travel of at least 0150inches 381mm desktop computer keyboards such as the 101key us traditional keyboards or the 104key windows keyboards include alphabetic characters punctuation symbols numbers and a variety of function keys the internationally common 102104 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 also the enter key is usually shaped differently computer keyboards are similar to electrictypewriter keyboards but contain additional keys such as the command or windows keys there is no standard computer keyboard although many manufacturers imitate the keyboard of pcs there are actually three different pc keyboards the original pc keyboard with 84 keys the at keyboard also with 84 keys and the enhanced keyboard with 101 keys the three differ somewhat in the placement of function keys the control keys the return key and the shift key laptopsize keyboards on laptops usually have a shorter travel distance and a reduced set of keys keyboards on laptops and notebook computers usually have a shorter travel distance for the keystroke shorter over travel distance and a reduced set of keys they may not have a numeric keypad and the function keys may be placed in locations that differ from their placement on a standard fullsized keyboard the switch mechanism for a laptop keyboard is more likely to be a scissor switch than a rubber dome this is opposite the trend for fullsize keyboards flexible keyboards flexible keyboards are a junction between normal type and laptop type keyboards normal from the full arrangement of keys and laptop from the short key distance additionally the flexibility allows the user to foldroll the keyboard for better storage and transfer however for typing the keyboard must be resting on a hard surface the vast majority where keyboards are subjected to frequent washing and other dirty or mustbeclean environments handheld an alphagrip handheld keyboard handheld ergonomic keyboards are designed to be held like a game controller and can be used as such instead of laid out flat on top of a table surface typically handheld keyboards hold all the alphanumeric keys and symbols that a standard keyboard would have yet only be accessed by pressing two sets of keys at once one acting as a function key similar to a shift key that would allow for capital letters on a standard keyboard thumbsized smaller external keyboards have been introduced for devices without a builtin keyboard such as pdas and smartphones small keyboards are also useful where there is a limited workspace a thumb keyboard thumb board is used in some personal digital assistants such as the palm treo and blackberry and some ultramobile 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 arithmetic operators numbers arrow keys navigation keys num lock and enter key multifunctional multifunction keyboard with lcd function keys multifunctional keyboards provide additional function beyond the standard keyboard many are programmable configurable computer keyboards and some control multiple pcs workstations incl sun and other information sources incl thomson reuters fxteikon bloomberg ebs etc usually in multiscreen work environments users have additional key functions as well as the standard functions and can typically use a single keyboard and mouse to access multiple sources multifunction keyboard with touch multifunctional keyboards may feature customised keypads fully programmable function or soft keys for macrospresets biometric or smart card readers trackballs etc new generation multifunctional keyboards feature a touchscreen display to stream video control audio visual media and alarms execute application inputs configure individual desktop environments etc multifunctional keyboards may also permit users to share access to pcs and other information sources multiple interfaces serial usb audio ethernet etc are used to integrate external devices some multifunctional keyboards are also used to directly and intuitively control video walls common environments for multifunctional keyboards are complex highperformance workplaces for financial traders and control room operators emergency services security air traffic management industry utilities management etc nonstandard layout and specialuse types chorded chorded keyboard while other keyboards generally associate one action with each key 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 the fastest typists as of 2007 use a stenograph a kind of chorded keyboard used by most court reporters and closedcaption 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 and on small mobile devices that dont 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 software software keyboards or onscreen 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 gnulinux include onscreen keyboards that can be controlled with the mouse in software keyboards the mouse has to be maneuvered onto the onscreen letters given by the software on the click of a letter the software writes the respective letter on the respective spot projection projection 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 users fingers move and will count a key as being pressed when it sees the users 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 nonreflective surface is also required for the keys to be projected most projection keyboards are made for use with pdas and smartphones due to their small form factor optical keyboard technology further information keyboard technology also known as photooptical keyboard light responsive keyboard photoelectric keyboard and optical key actuation detection technology an optical keyboard technology require at least 2 beams most commonly vertical beam and horizontal beam to determine the actuated key 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 layout alphabetic keyboard layout the 104key pc us english qwerty keyboard layout evolved from the standard typewriter keyboard with extra keys for computing the dvorak simplified keyboard layout arranges keys so that frequently used keys are easiest to press which reduces muscle fatigue when typing common english there are a number of different arrangements of alphabetic numeric and punctuation symbols on keys these different keyboard layouts arise mainly because different people need easy access to different symbols either because they are inputting text in different languages or because they need a specialized layout for mathematics accounting computer programming or other purposes the united states keyboard layout is used as default in the currently most popular operating systems windows the common qwertybased layout was designed early in the era of mechanical typewriters so its ergonomics were compromised to allow for the mechanical limitations of the typewriter as the letterkeys were attached to levers that needed to move freely inventor christopher sholes developed the qwerty layout to reduce the likelihood of jamming with the advent of computers lever jams are no longer an issue but nevertheless qwerty layouts were adopted for electronic keyboards because they were widely used alternative layouts such as the dvorak simplified keyboard 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 national layouts keyboards designed for typing in spanish have some characters shifted to release the space for similarly those for portuguese french and other european languages may have a special key for the character the azerty layout is used in france belgium and some neighbouring countries it differs from the qwerty layout in that the a and q are swapped the z and w are swapped and the m is moved from the right of n to the right of l where colonsemicolon is on a us keyboard the digits 0 to 9 are on the same keys but to be typed the shift key must be pressed the unshifted positions are used for accented characters keyboards in many parts of asia may have special keys to switch between the latin character set and a completely different typing system japanese layout keyboards can be switched between various japanese input methods and the latin alphabet by signaling the operating systems input interpreter of the change and some operating systems namely the windows family interpret the character as for display purposes without changing the bytecode which has led some keyboard makers to mark as or both in the arab world keyboards can often be switched between arabic and latin characters in bilingual regions of canada and in the frenchspeaking province of qubec keyboards can often be switched between an english and a frenchlanguage keyboard while both keyboards share the same qwerty alphabetic layout the frenchlanguage keyboard enables the user to type accented vowels such as or with a single keystroke using keyboards for other languages leads to a conflict the image on the key does not correspond to the character in such cases each new language may require an additional label on the keys because the standard keyboard layouts do not share even similar characters of different languages see the example in the figure above key types alphanumeric a hebrew keyboard lets the user type in both hebrew and the latin alphabet a greek keyboard lets the user type in both greek and the latin alphabet macbook pro the control windows and alt keys are important modifier keys a spacecadet keyboard has many modifier keys alphabetical numeric and punctuation keys are used in the same fashion as a typewriter keyboard to enter their respective symbol into a word processing program text editor data spreadsheet or other program many of these keys will produce different symbols when modifier keys or shift keys are pressed the alphabetic characters become uppercase when the shift key or caps lock key is depressed the numeric characters become symbols or punctuation marks when the shift key is depressed the alphabetical numeric and punctuation keys can also have other functions when they are pressed at the same time as some modifier keys the space bar is a horizontal bar in the lowermost row which is significantly wider than other keys like the alphanumeric characters it is also descended from the mechanical typewriter its main purpose is to enter the space between words during typing it is large enough so that a thumb from either hand can use it easily depending on the operating system when the space bar is used with a modifier key such as the control key it may have functions such as resizing or closing the current window halfspacing or backspacing in computer games and other applications the key has myriad uses in addition to its normal purpose in typing such as jumping and adding marks to check boxes in certain programs for playback of digital video the space bar is used for pausing and resuming the playback modifier keys modifier keys are special keys that modify the normal action of another key when the two are pressed in combination for example altf4 in microsoft windows will close the program in an active window in contrast pressing just f4 will probably do nothing unless assigned a specific function in a particular program by themselves modifier keys usually do nothing the most widely used modifier keys include the control key shift key and the alt key the altgr key is used to access additional symbols for keys that have 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 used as a modifier and for windows keyboards there is a windows key compact keyboard layouts often use a fn key dead keys allow placement of a diacritic mark such as an accent on the following letter eg the compose key the enterreturn key typically causes a command line window form or dialog box to operate its default function which is typically to finish an entry and begin the desired process in word processing applications pressing the enter key ends a paragraph and starts a new one cursor keys navigation keys or cursor keys include a variety of keys which move the cursor to different positions on the screen arrow keys are programmed to move the cursor in a specified direction page scroll keys such as the page up and page down keys scroll the page up and down the home key is used to return the cursor to the beginning of the line where 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 insert key is mainly used to switch between overtype mode in which the cursor overwrites any text that is present on and after its current location and insert mode where the cursor inserts a character at its current position forcing all characters past it one position further the delete key discards the character ahead of the cursors position moving all following characters one position back towards the freed place on many notebook computer keyboards the key labeled delete sometimes delete and backspace are printed on the same key serves the same purpose as a backspace key the backspace key deletes the preceding character lock keys lock part of a keyboard depending on the settings selected the lock keys are scattered around the keyboard most styles of keyboards have three leds indicating which locks are enabled in the upper right corner above the numeric pad the lock keys include scroll lock num lock which allows the use of the numeric keypad and caps lock system commands 480052 mainframe dumb terminal keyboard circa mid 1980s note the obscure configuration of modifier and arrow keys line feed key break key blank keys and repeat key the sysrq and print screen commands often share the same key sysrq was used in earlier computers as a panic button to recover from crashes and it is still used in this sense to some extent by the linux kernel see magic sysrq key the print screen command used to capture the entire screen and send it to the printer but in the present it usually puts a screenshot in the clipboard break key the break keypause key no longer has a welldefined purpose its origins go back to teleprinter users who wanted a key that would temporarily interrupt the communications line the break key can be used by software in several different ways such as to switch between multiple login sessions to terminate a program or to interrupt a modem connection in programming especially old dosstyle basic pascal and c break is used in conjunction with ctrl to stop program execution in addition to this linux and variants as well as many dos programs treat this combination the same as ctrlc on modern keyboards the break key is usually labeled pausebreak in most windows environments the key combination windows keypause brings up the system properties escape key esc key the escape key often abbreviated esc nearly all of the time let me escape another common application today of the esc key isto trigger the stop button in many web browsers esc origins esc was part of the standard keyboard on the dec vt50 introduced july 1974 it was not part of the 1970introduced vt05 the teco and emacs text editors use the esc key extensively historically it also served as a type of shift key such that one or more following characters were interpreted differently hence the term escape sequence which refers to a series of characters usually preceded by the escape character on machines running microsoft windows prior to the implementation of the windows key on keyboards the typical practice for invoking the start button was to hold down the control key and press escape this process still works in windows 95 98 me nt 4 2000 xp vista 7 8 and 10 enter key the enter key is located one in the alphanumeric keys and the other one is in the numeric keys when one worked something on their computer and wanted to do something with their work pressing the enter key would do the command they ordered another function is to create a space for next paragraph when one typed and finished typing a paragraph and they wanted to have a second paragraph they could press enter and it would do spacing shift key shift key when one presses shift and a letter it will capitalize the letter pressed with the shift key another use is to type more symbols than appear to be available for instance the apostrophe key is accompanied with a quotation mark on the top if one wants to type the quotation mark but pressed that key alone the symbol that would appear would be the apostrophe the quotation mark will only appear if both the required key and the shift key are pressed menu key the menu key or application key is a key found on windowsoriented computer keyboards it is used to launch a context menu with the keyboard rather than with the usual right mouse button the keys symbol is usually a small icon depicting a cursor hovering above a menu on some samsung keyboards the cursor in the icon is not present showing the menu only this key was created at the same time as the windows key this key is normally used when the right mouse button is not present on the mouse some windows public terminals do not have a menu key on their keyboard to prevent users from rightclicking however in many windows applications a similar functionality can be invoked with the shiftf10 keyboard shortcut miscellaneous multimedia buttons on some keyboards give quick access to the internet or control the volume of the speakers many but not all computer keyboards have a numeric keypad to the right of the alphabetic keyboard often separated from the other groups of keys such as the function keys and system command keys which contains numbers basic mathematical symbols eg addition subtraction etc and a few function keys on japanesekorean keyboards there may be language input keys for changing the language to use some keyboards have power management keys eg power key sleep key and wake key internet keys to access a web browser or email andor multimedia keys such as volume controls or keys that can be programmed by the user to launch a specified application or a command like minimizing all windows numeric keys when we calculate we use these numeric keys to type numbers symbols concerned with calculations such as addition subtraction multiplication and division symbols are located in this group of keys the enter key in this keys indicate the equal sign multiple layouts it is possible to install multiple keyboard layouts within an operating system and switch between them either through features implemented within the os or through an external application microsoft windows provide support to add keyboard layouts and choose from them layout changing software the character code produced by any key press is determined by the keyboard driver software a key press generates a scancode which is interpreted as an alphanumeric character or control function depending on operating systems various application programs are available to create add and switch among keyboard layouts many programs are available some of which are language specific the arrangement of symbols of specific language can be customized an existing keyboard layout can be edited and a new layout can be created using this type of software for example ukelele and opensource avro keyboard for windows provide the ability to customize the keyboard layout as desired illumination keyboards and keypads may be illuminated from inside especially on equipment for mobile use illumination facilitates the use of the keyboard or keypad in dark environments some gaming keyboards have lighted keys to make it easier for gamers to find command keys while playing in a dark room some keyboards may have small led lights in a few important function keys to remind users that the function is activated see photo keys with integrated led indicator lights technology keyboard technology key switches in the first electronic keyboards in the early 1970s the key switches were individual switches inserted into holes in metal frames these keyboards cost from 80 to 120usd and were used in mainframe data terminals the most popular switch types were reed switches contacts enclosed in a vacuum in a glass capsule affected by a magnet mounted on the switch plunger in the mid1970s lowercost directcontact key switches were introduced but their life in switch cycles was much shorter rated ten million cycles because they were open to the environment this became more acceptable however for use in computer terminals at the time which began to see increasingly shorter model lifespans as they advanced in 1978 key tronic corporation introduced keyboards with capacitivebased switches one of the first keyboard technologies not to use selfcontained switches there was simply a sponge pad with a conductivecoated mylar plastic sheet on the switch plunger and two halfmoon trace patterns on the printed circuit board below as the key was depressed the capacitance between the plunger pad and the patterns on the pcb below changed which was detected by integrated circuits ic these keyboards were claimed to have the same reliability as the other solidstate switch keyboards such as inductive and halleffect but competitive with directcontact keyboards prices of 60 for keyboards were achieved and key tronic rapidly became the largest independent keyboard manufacturer meanwhile ibm made their own keyboards using their own patented technology keys on older ibm keyboards the first electronic keyboards had a typewriter key travel distance of 0187inches 475mm keytops were a halfinch 127mm high and keyboards were about two inches 5cm thick over time less key travel was accepted in the market finally landing on 0110inches 279mm coincident with this key tronic was the first company to introduce a keyboard that was only about one inch thick and now keyboards measure only about a halfinch thick keytops are an important element of keyboards in the beginning keyboard keytops had a dish shape on top like typewriters before them keyboard key legends must be extremely durable over tens of millions of depressions since they are subjected to extreme mechanical wear from fingers and fingernails and subject to hand oils and creams so engraving and filling key legends with paint as was done previously for individual switches was never acceptable so for the first electronic keyboards the key legends were produced by twoshot or doubleshot or twocolor molding where either the key shell or the inside of the key with the key legend was molded first and then the other color molded second but to save cost other methods were explored such as sublimation printing and laser engraving both methods which could be used to print a whole keyboard at the same time initially sublimation printing where a special ink is printed onto the keycap surface and the application of heat causes the ink molecules to penetrate and commingle with the plastic modules had a problem because finger oils caused the molecules to disperse but then a necessarily very hard clear coating was applied to prevent this coincident with sublimation printing which was first used in high volume by ibm on their keyboards was the introduction by ibm of singlecurveddish keycaps to facilitate quality printing of key legends by having a consistently curved surface instead of a dish but one problem with sublimation or laser printing was that the processes took too long and only dark legends could be printed on lightcolored keys on another note ibm was unique in using separate shells or keycaps on keytop bases this might have made their manufacturing of different keyboard layouts more flexible but the reason for doing this was that the plastic material that needed to be used for sublimation printing was different from standard abs keytop plastic material three final mechanical technologies brought keyboards to where they are today driving the cost well under 10 monoblock keyboard designs were developed where individual switch housings were eliminated and a onepiece monoblock housing used instead this was possible because of molding techniques that could provide very tight tolerances for the switchplunger holes and guides across the width of the keyboard so that the key plungertohousing clearances were not too tight or too loose either of which could cause the keys to bind the use of contactswitch membrane sheets under the monoblock this technology came from flatpanel switch membranes where the switch contacts are printed inside of a top and bottom layer with a spacer layer in between so that when pressure is applied to the area above a direct electrical contact is made the membrane layers can be printed by veryhigh volume lowcost reeltoreel printing machines with each keyboard membrane cut and punched out afterwards plastic materials played a very important part in the development and progress of electronic keyboards until monoblocks came along ges selflubricating delrin was the only plastic material for keyboard switch plungers that could withstand the beating over tens of millions of cycles of lifetime use greasing or oiling switch plungers was undesirable because it would attract dirt over time which would eventually affect the feel and even bind the key switches although keyboard manufacturers would sometimes sneak this into their keyboards especially if they could not control the tolerances of the key plungers and housings well enough to have a smooth key depression feel or prevent binding but delrin was only available in black and white and was not suitable for keytops too soft so keytops use abs plastic however as plastic molding advanced in maintaining tight tolerances and as key travel length reduced from 0187inch to 0110inch 475mm to 279mm singlepart keytopplungers could be made of abs with the keyboard monolocks also made of abs control processor scanning procedure computer keyboards include control circuitry to convert key presses into key codes usually scancodes that the computers electronics can understand the key switches are connected via the printed circuit board in an electrical xy matrix where a voltage is provided sequentially to the y lines and when a key is depressed detected sequentially by scanning the x lines the first computer keyboards were for mainframe computer data terminals and used discrete electronic parts the first keyboard microprocessor was introduced in 1972 by general instruments but keyboards have been using the singlechip 8048 microcontroller variant since it became available in 1978 the keyboard switch matrix is wired to its inputs it converts the keystrokes to key codes and for a detached keyboard sends the codes down a serial cable the keyboard cord to the main processor on the computer motherboard this serial keyboard cable communication is only bidirectional to the extent that the computers electronics controls the illumination of the caps lock num lock and scroll lock lights one test for whether the computer has crashed is pressing the caps lock key the keyboard sends the key code to the keyboard driver running in the main computer if the main computer is operating it commands the light to turn on all the other indicator lights work in a similar way the keyboard driver also tracks the shift alt and control state of the keyboard some lowerquality keyboards have multiple or false key entries due to inadequate electrical designs these are caused by inadequate keyswitch debouncing or inadequate keyswitch matrix layout that dont allow multiple keys to be depressed at the same time both circumstances which are explained below when pressing a keyboard key the key contacts may bounce against each other for several milliseconds before they settle into firm contact when released they bounce some more until they revert to the uncontacted state if the computer were watching for each pulse it would see many keystrokes for what the user thought was just one to resolve this problem the processor in a keyboard or computer debounces the keystrokes by aggregating them across time to produce one confirmed keystroke some lowquality keyboards also suffer problems with rollover that is when multiple keys pressed at the same time or when keys are pressed so fast that multiple keys are down within the same milliseconds early solidstate keyswitch keyboards did not have this problem because the keyswitches are electrically isolated from each other and early directcontact keyswitch keyboards avoided this problem by having isolation diodes for every keyswitch these early keyboards had nkey rollover which means any number of keys can be depressed and the keyboard will still recognize the next key depressed but when three keys are pressed electrically closed at the same time in a direct contact keyswitch matrix that doesnt have isolation diodes the keyboard electronics can see a fourth phantom key which is the intersection of the x and y lines of the three keys some types of keyboard circuitry will register a maximum number of keys at one time threekey rollover also called phantom key blocking or phantom key lockout will only register three keys and ignore all others until one of the three keys is lifted this is undesirable especially for fast typing hitting new keys before the fingers can release previous keys and games designed for multiple key presses as directcontact membrane keyboards became popular the available rollover of keys was optimized by analyzing the most common key sequences and placing these keys so that they do not potentially produce phantom keys in the electrical key matrix for example simply placing three or four keys that might be depressed simultaneously on the same x or same y line so that a phantom key intersectionshort cannot happen so that blocking a third key usually isnt a problem but lowerquality keyboard designs and unknowledgeable engineers may not know these tricks and it can still be a problem in games due to wildly different or configurable layouts in different games connection types there are several ways of connecting a keyboard to a system unit more precisely to its keyboard controller using cables including the standard at connector commonly found on motherboards which was eventually replaced by the ps2 and the usb connection prior to the imac line of systems apple used the proprietary apple desktop bus for its keyboard connector wireless keyboards have become popular for their increased user freedom a wireless keyboard often includes a required combination transmitter and receiver unit that attaches to the computers keyboard port the wireless aspect is achieved either by radio frequency rf or by infrared ir signals sent and received from both the keyboard and the unit attached to the computer a wireless keyboard may use an industry standard rf called bluetooth with bluetooth the transceiver may be built into the computer however a wireless keyboard needs batteries to work and may pose a security problem due to the risk of data eavesdropping by hackers wireless solar keyboards charge their batteries from small solar panels using sunlight or standard artificial lighting an early example of a consumer wireless keyboard is that of the olivetti envision alternative textentering methods onscreen keyboard controlled with the mouse can be used by users with limited mobility optical character recognition ocr is preferable to rekeying for converting existing text that is already written down but not in machinereadable format for example a linotypecomposed book from the 1940s in other words to convert the text from an image to editable text that is a string of character codes a person could retype it or a computer could look at the image and deduce what each character is ocr technology has already reached an impressive state for example google book search and promises more for the future speech recognition converts speech into machinereadable text that is a string of character codes this technology has also reached an advanced state and is implemented in various software products for certain uses eg transcription of medical or legal dictation journalism writing essays or novels speech recognition is starting to replace the keyboard however the lack of privacy when issuing voice commands and dictation makes this kind of input unsuitable for many environments pointing devices can be used to enter text or characters in contexts where using a physical keyboard would be inappropriate or impossible these accessories typically present characters on a display in a layout that provides fast access to the more frequently used characters or character combinations popular examples of this kind of input are graffiti dasher and onscreen virtual keyboards other issues keystroke logging unencrypted wireless bluetooth keyboards are known to be vulnerable to signal theft by placing a covert listening device in the same room as the keyboard to sniff and record bluetooth packets for the purpose of logging keys typed by the user microsoft wireless keyboards 2011 and earlier are documented to have this vulnerability 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 computers 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 antispyware applications are able to detect many keyloggers and cleanse them responsible vendors of monitoring software support detection by antispyware 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 reversefirewalls 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 formfilling 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 keyboards are also known to emit electromagnetic signatures that can be detected using special spying equipment to reconstruct the keys pressed on the keyboard neal ofarrell executive director of the identity theft council revealed to informationweek that more than 25 years ago a couple of former spooks showed me how they could capture a users atm pin from a van parked across the street simply by capturing and decoding the electromagnetic signals generated by every keystroke ofarrell said they could even capture keystrokes from computers in nearby offices but the technology wasnt sophisticated enough to focus in on any specific computer 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 longterm disability 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 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 by using a touchpad or a stylus pen with a graphic tablet in place of a mouse one can lessen the repetitive strain on the arms and hands pathogen transmission some keyboards were found to contain five times more potentially harmful germs than a toilet seat this can be a concern when using shared keyboards the keyboards can serve as vectors for pathogens that cause the cold flu and other communicable diseases easily spread by indirect contact digital pen ibm pc keyboard keyboard protector overlay keyboard table of keyboard shortcuts dvorak simplified keyboard wikimedia commons has media related to keyboards how computer keyboards work at howstuffworks art of assembly language chapter twenty the pc keyboard keyboard matrix circuits pc world the 10 worst pc keyboards of all time ibm pc keyboard windows us layoutvte esc f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 prtscnsysrq scrolllock pausebreak insert home pgup numlock delete end pgdn 7 8 9 4 5 6 1 2 3 enter 0 ins del vtekeyboard keysdead keys compose modifier keys control shift alt option apple altgr meta command apple windows microsoft super hyper fn lock keys scroll lock num lock caps lock flock navigation keys arrow keys page uppage down home end esc menu editing enterreturn carriage return backspace insert delete tab space bar numeric keypad language input contextual function keys print screen system request breakpause misc power management keys power sleep wake any key macro key concepts keyboard layout keyboard shortcut vtebasic computer componentsinput devices keyboard image scanner microphone pointing device graphics tablet joystick light pen mouse optical pointing stick touchpad touchscreen trackball refreshable braille display sound card webcam softcam video card output devices monitor refreshable braille display printer speakers plotter sound card video card removable data storage optical disc cd dvd bluray disk pack floppy disk memory card usb flash drive computer case central processing unit cpu hdd ssd sshd motherboard network interface controller power supply randomaccess memory ram fax modem expansion card ports ethernet firewire ieee 1394 parallel port serial port ps2 port usb thunderbolt displayport hdmi dvi vga esata audio jack vtevideo game controllerscontroller types arcade controller balance board digital camera dance pad fishing rod gamepad gaming keypad interactive urinal joystick keyboard light gun microphone motion controller mouse musical instruments nunchaku paddle racing wheel remote control throttle quadrant virtual reality headset wired glove controller partsphysical buttons analog stick arrow keys circle pad dpad discpad face button scroll wheel select button shoulder button start button telephone keypad trigger turbo button sensitive accelerometer haptic technology stylus pen touchpad touchscreen trackball related multitap rob 