In computing, a computer keyboard is a typewriter-style 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 teleprinter-style keyboards became the main input method for computers. Keyboard keys have characters engraved or printed on them, each press of a key corresponds to a single written symbol. However, producing some symbols may require pressing and holding several keys or in sequence. While most keyboard keys produce letters, numbers or signs, 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 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 used for computer gaming — either regular keyboards or keyboards with special gaming features, which can expedite used keystroke combinations. A keyboard is used to give commands to the operating system of a computer, such as Windows' Control-Alt-Delete combination. Although on Pre-Windows 95 Microsoft operating systems this forced a re-boot, now it brings up a system security options screen. A command-line interface is a type of user interface navigated using a keyboard, or some other similar device that does the job of one. While typewriters are the definitive ancestor of all key-based text entry devices, the computer keyboard as a device for electromechanical data entry and communication derives from the utility of two devices: teleprinters and keypunches, it was through such devices. As early as the 1870s, teleprinter-like devices were used to type and transmit stock market text data from the keyboard across telegraph lines to stock ticker machines to be 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 point-to-point and point-to-multipoint communication for most of the 20th century, while the keyboard on the keypunch device played a strong role in data entry and storage for just as long. The development of the earliest computers incorporated electric typewriter keyboards: the development of the ENIAC computer incorporated a keypunch device as both the input and paper-based output device, while the BINAC computer made use of an electromechanically controlled typewriter for both data entry onto magnetic tape 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, text-only user interfaces with sparse graphics gave way to comparatively graphics-rich icons on screen. However, keyboards remain central to human-computer interaction to the present as mobile personal computing devices such as smartphones and tablets adapt the keyboard as an optional virtual, touchscreen-based means of data entry. 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, 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 spacing of the keys.
Reduction is limited by the practical consideration that the keys must be large enough to be pressed by fingers. Alternatively a tool is used for pressing small keys. Standard alphanumeric keyboards have keys that are on three-quarter inch centers, have a key travel of at least 0.150 inches. Desktop computer keyboards, such as the 101-key US traditional keyboards or the 104-key Windows keyboards, include alphabetic characters, punctuation symbols, numbers and a variety of function keys; the internationally common 102/104 key keyboards have a smaller left shift key and an additional key with some more symbols between that and the letter to its right. The enter key is shaped differently. Computer keyboards are similar to electric-typewriter keyboards but contain additional keys, such as the command or Windows keys. There is no standard computer keyboard. There are three different PC keyboards: the original PC keyboard with 84 keys, the AT keyboard 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, the shift key. Keyboards on laptops and notebook computers have a shorter travel distance for the keystroke, shorter over travel distance, a reduced set of keys, they may not have a numeric keypad, the function keys may be placed in locations that differ from their placement on a standard, full-sized keyboard. The switch
The tilde is a grapheme with several uses. The name of the character came into English from Spanish and from Portuguese, which in turn came from the Latin titulus, meaning "title" or "superscription"; the reason for the name was that it was written over a letter as a scribal abbreviation, as a "mark of suspension", shown as a straight line when used with capitals. Thus the used words Anno Domini were abbreviated to Ao Dñi, an elevated terminal with a suspension mark placed over the "n"; such a mark could denote the omission of several letters. This saved on the cost of vellum and ink. Medieval European charters written in Latin are made up of such abbreviated words with suspension marks and other abbreviations; the tilde has since been applied to a number of other uses as a diacritic mark or a character in its own right. These are encoded in Unicode at U+0303 ◌̃ COMBINING TILDE and U+007E ~ TILDE, there are additional similar characters for different roles. In lexicography, the latter kind of tilde and the swung dash are used in dictionaries to indicate the omission of the entry word.
This symbol informally means "approximately", "about", or "around", such as "~30 minutes before", meaning "approximately 30 minutes before". It can mean "similar to", including "of the same order of magnitude as", such as: "x ~ y" meaning that x and y are of the same order of magnitude. Another approximation symbol is the double-tilde ≈, meaning "approximately equal to", the critical difference being the subjective level of accuracy: ≈ indicates a value which can be considered functionally equivalent for a calculation within an acceptable degree of error, whereas ~ is used to indicate a larger significant, degree of error; the tilde is used to indicate "equal to" or "approximately equal to" by placing it over the "=" symbol, like so: ≅. In the computing field in Unix based systems, the tilde indicates the user's home directory; the text of the Domesday Book of 1086, relating for example, to the manor of Molland in Devon, is abbreviated as indicated by numerous tildes. The text with abbreviations expanded is as follows: Mollande tempore regis Edwardi geldabat pro quattuor hidis et uno ferling.
Terra est quadraginta carucae. In dominio sunt tres carucae et decem servi et triginta villani et viginta bordarii cum sedecim carucis. Ibi duodecim acrae prati et quindecim acrae silvae. Pastura tres leugae in longitudine et latitudine. Libras ad pensam. Huic manerio est adjuncta Blachepole. Elwardus tenebat tempore regis Edwardi pro manerio et geldabat pro dimidia hida. Terra est duae carucae. Ibi sunt quinque villani cum uno servo. Valet viginti solidos arsuram. Eidem manerio est injuste adjuncta Nimete et valet quindecim solidos. Ipsi manerio pertinet tercius denarius de Hundredis Nortmoltone et Badentone et Brantone et tercium animal pasturae morarum; the incorporation of the tilde into ASCII is a direct result of its appearance as a distinct character on mechanical typewriters in the late nineteenth century. When all character sets were pieces of metal permanently installed, number of characters much more limited than in typography, the question of which languages and markets required which characters was an important one.
Any good typewriter store had a catalog of alternative keyboards that could be specified for machines ordered from the factory. At that time, the tilde was used only in Portuguese typewriters. In Modern Spanish, the tilde is used only with ñ and Ñ. Both were conveniently assigned to a single mechanical typebar, which sacrificed a key, felt to be less important the ½—¼ key. Portuguese, uses not ñ but nh, it uses the tilde on the vowels a and o. So as not to sacrifice two of the limited keys to ã Ã õ Õ, the decision was made to make the ~ a separate "dead" character in which the carriage holding the paper did not move. Dead keys, which had a notch cut out to avoid hitting a mechanical linkage that triggered carriage movement, were used for characters that were intended to be combined. On mechanical typewriters, Spanish keyboards had a dead key, which contained the acute accent, used over any vowel, the dieresis, used only over u, it was a simple matter to create a dead key for a Portuguese keyboard to be overstruck with a and o and so the ~ was born as a typographical character, which did not exist as a type or hot-lead printing character.
That was a product of the first and leading manufacturer of typewriters, Remington. As indicated by the etymological origin of the word "tilde" in English, this symbol has been associated with the Spanish language; the connection stems from the use of the tilde above the letter "n" to form "ñ" in Spanish, a feature shared by only a few other languages, all connected to Spanish. This peculiarity can help non-native speakers identify a text as being written in Spanish with little chance of error. In addition, most native speakers, although not all, use the word "español" to refer to their language. During the 1990s, Spanish-speaking intellectuals and news outlets demonstrated support for the language and the culture by defending this letter against globalisation and computerisation trends that threatened to remove it from keyboards and other standardised products and codes; the Instituto Cervantes, founded by Spain's government to promote the Spanish language internationally, chose as its logo a stylised Ñ with a large tilde.
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On computer keyboards, the Esc key is a key used to generate the escape character. The escape character, when sent from the keyboard to a computer is interpreted by software as "stop", when sent from the computer to an external device marks the beginning of an escape sequence to specify operating modes or characteristics generally, it is now placed at the top left corner of the keyboard, a convention dating at least to the original IBM PC keyboard, though the key itself originated decades earlier with teletypewriters. The keyboard symbol for the ESC key is standardized in ISO/IEC 9995-7 as symbol 29, in ISO 7000 "Graphical symbols for use on equipment" as symbol ISO-7000-2029; this symbol is encoded in Unicode as U+238B broken circle with northwest arrow. The name of the equivalent key on some early Teletype Model 33 keyboards was labeled Alt Mode... the alternative mode of operation causing the escapement to treat the following one character in a special way. Much printers and computer terminals that would use escape sequences would take more than one following byte as part of a special sequence.
The VT05 CRT did not have an ESC key. As most computer users are no longer concerned with the details of controlling their computer's peripherals, the task for which the escape sequences were designed, the escape key was appropriated by application programmers, most to mean Stop; this use continues today in Microsoft Windows's use of escape as a shortcut in dialog boxes for No, Exit, Cancel, or Abort, as well as a common shortcut key for the Stop button in many web browsers. 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 key combination still works as of Windows 10. Microsoft Windows makes use of "Esc" for many key shortcuts. Many of these shortcuts have been present since Windows 3.0, through Windows XP, Windows Vista, Windows 7, Windows 8, Windows 10. In macOS, "Esc" closes or cancels a dialog box or sheet; the ⌘ Command+⌥ Option+⎋ Esc combination opens the Force Quit dialog box, allowing users to end non-responsive applications.
Another use for the Esc key, in combination with the Command key, is switching to Front Row, if installed. In most computer games, the escape key is used as a pause button and/or as a way to bring up the in-game menu containing ways to exit the program. In the vi family of text editors, escape is used to switch modes; this usage is due to escape being conveniently placed in what is now the tab position on the ADM-3A terminal keyboard used to develop vi, though it is now inconveniently placed. This is similar to how the extensive modifier keys in Emacs were used on the original keyboard, being placed together, but these keys have now been spread around the keyboard, becoming more difficult to use. Old keyboard Send/Receive printers, visual display units, would be controlled by escape sequences sent by the computer to the peripheral device, but there were situations where these devices could be used "off-line" with the keyboard connected to the output device, so the need could arise to type escape sequences "by hand" to control the peripheral.
Although such devices are long out of use, standard processing of ANSI Escape sequences similar to 1970's VT100, is implemented in both ANSI. SYS and other more modern pseudo-terminal interfaces used in Unix-like environments, one example being Linux consoles, meaning newer, higher-level abstractions haven't changed the fact that typing the escape key followed by something like the six characters [32.
The at sign, @, is read aloud as "at" or "at symbol":. It is used as an accounting and invoice abbreviation meaning "at a rate of", but it is now most used in email addresses and social media platform "handles"; the term "alphasand" is sometimes used to refer to "@" in East Asia. Although not included on the keyboard of the earliest commercially successful typewriters, it was on at least one 1889 model and the successful Underwood models from the "Underwood No. 5" in 1900 onward. It started to be used in email addresses in the 1970s, is now universally included on computer keyboards; the absence of a single English word for the symbol has prompted some writers to use the French arobase or Spanish and Portuguese arroba, or to coin new words such as ampersat and strudel, but none of these has achieved wide use. In unicode, the at sign is encoded as & commat; the earliest yet discovered. Held today in the Vatican Apostolic Library, it features the @ symbol in place of the capital letter alpha "Α" in the word Amen.
Why it was used in this context is still a mystery. In terms of the commercial character of the at sign, there are several theories pending verification. One theory is that the symbol developed as a mercantile shorthand symbol of "each at," the symbol resembling a lowercase "a" inside a lowercase "e," to distinguish it from the different "at" or "per." For example, the cost of "12 apples @ $1" would be $12, whereas the cost of "12 apples at $1" would be $1, a crucial and necessary distinction. Another theory is. One reason for the abbreviation saving space and ink. Since thousands of pages of biblical manuscripts were copied onto expensive papyrus or hides, the words at, toward, by and about repeated millions of times throughout the pages, a considerable amount of resources could be spared this way. A theory concerning this graph puts forward the idea that the form derives from the Latin word ad, using the older form of lowercase d: ∂ used in handwritten German well into the 20th century and known to mathematicians and engineering students as the partial derivative symbol.
It has been theorized that it was an abbreviation of the Greek preposition ανά, meaning at the rate of or per. Another theory is that it derives from the Norman French "à" meaning "at" in the "each" sense, i.e. "2 widgets à £5.50 = £11.00", comes the accountancy shorthand notation in English commercial vouchers and ledgers to the 1990s, when the email usage overtook the accountancy usage. It is used like this in Modern French, Swedish or Czech; the compromise between @ and à in French handwriting is found in street market signs. Whatever the origin of the @ symbol, the history of its usage is more well-known: it has long been used in Spanish and Portuguese as an abbreviation of arroba, a unit of weight equivalent to 25 pounds, derived from the Arabic expression of "the quarter". An Italian academic, Giorgio Stabile, claims to have traced the @ symbol to the 16th century, in a mercantile document sent by Florentine Francesco Lapi from Seville to Rome on May 4, 1536; the document is in particular the price of an @ of wine in Peru.
In Italian, the symbol was interpreted to mean amphora. The word arroba means both the at-symbol and a unit of weight. In Italian, the symbol represents one amphora, a unit of weight and volume based upon the capacity of the standard amphora jar; until now the first historical document containing a symbol resembling a @ as a commercial one is the Spanish "Taula de Ariza", a registry to denote a wheat shipment from Castile to Aragon in 1448. In contemporary English usage, @ is a commercial symbol, called at site or at rate meaning at and at the rate of, it has been used in financial documents or grocers' price tags, is not used in standard typography. In 2012, "@" was registered as a trademark with the German Patent and Trade Mark Office. A cancellation request was filed in 2013, the cancellation was confirmed by the German Federal Patent Court in 2017. A common contemporary use of @ is in email addresses, as in firstname.lastname@example.org. BBN Technologies' Ray Tomlinson is credited with introducing this usage in 1971.
This idea of the symbol representing located at in the form user@host is seen in other tools and protocols. On web pages, organizations obscure email addresses of their members or employees by omitting the @; this practice, known as address munging, makes the email addresses less vulnerable to spam programs that scan the internet for them. On some social media platforms and forums, usernames are in the form @johndoe. On online forums without threaded discussions, @ is used to denote a reply. In some cases, @ is used for "attention" in email message
Cursor (user interface)
In computer user interfaces, a cursor is an indicator used to show the current position for user interaction on a computer monitor or other display device that will respond to input from a text input or pointing device. The mouse cursor is called a pointer, owing to its resemblance in usage to a pointing stick. Cursor is Latin for'runner.' A cursor is the name given to the transparent slide engraved with a hairline, used for marking a point on a slide rule. The term was transferred to computers through analogy. In most command-line interfaces or text editors, the text cursor known as a caret, is an underscore, a solid rectangle, or a vertical line, which may be flashing or steady, indicating where text will be placed when entered. In text mode displays, it was not possible to show a vertical bar between characters to show where the new text would be inserted, so an underscore or block cursor was used instead. In situations where a block was used, the block was created by inverting the pixels of the character using the boolean math exclusive or function.
On text editors and word processors of modern design on bitmapped displays, the vertical bar is used instead. In a typical text editing application, the cursor can be moved by pressing various keys; these include the four arrow keys, the Page Up and Page Down keys, the Home key, the End key, various key combinations involving a modifier key such as the Control key. The position of the cursor may be changed by moving the mouse pointer to a different location in the document and clicking; the blinking of the text cursor is temporarily suspended when it is being moved. Some interfaces use an underscore or thin vertical bar to indicate that the user is in insert mode, a mode where text will be inserted in the middle of the existing text, a larger block to indicate that the user is in overtype mode, where inserted text will overwrite existing text. In this way, a block cursor may be seen as a piece of selected text one character wide, since typing will replace the text "in" the cursor with the new text.
A vertical line text cursor with a small left-pointing or right-pointing appendage are for indicating the direction of text flow on systems that support bi-directional text, is thus known among programmers as a'bidi cursor'. In some cases, the cursor may split into two parts, each indicating where left-to-right and right-to-left text would be inserted; the pointer or mouse cursor echoes movements of the pointing device a mouse, touchpad or trackball. This kind of cursor is used to manipulate elements of graphical user interfaces such as menus, scrollbars or any other widget, it may be called a "mouse pointer," because the mouse is the dominant type of pointing device used with desktop computers. The I-beam pointer is a cursor shaped like a serifed capital letter "I"; the purpose of this cursor is to indicate that the text beneath the cursor can be highlighted, sometimes inserted or changed. The idea of a cursor being used as a marker or insertion point for new data or transformations, such as rotation, can be extended to a 3D modeling environment.
Blender, for instance, uses a 3D cursor to determine. Susan Kare, designer of several of the common cursor shapes Creating and controlling browser cursors Cross-browser CSS custom cursors Installing A Cursor On Your Computer
An asterisk. It is so called. Computer scientists and mathematicians vocalize it as star. In English, an asterisk is five-pointed in sans-serif typefaces, six-pointed in serif typefaces, six- or eight-pointed when handwritten, it is used to censor offensive words, on the Internet, to indicate a correction to a previous message. In computer science, the asterisk is used as a wildcard character, or to denote pointers, repetition, or multiplication; the asterisk derives from the two thousand year old character used by Aristarchus of Samothrace called the asteriskos, ※, which he used when proofreading Homeric poetry to mark lines that were duplicated. Origen is known to have used the asteriskos to mark missing Hebrew lines from his Hexapla; the asterisk evolved in shape over time, but its meaning as a symbol used to correct defects remained. In the Middle Ages, the asterisk was used to emphasize a particular part of text linking those parts of the text to a marginal comment. However, an asterisk was not always used.
One hypothesis to the origin of the asterisk is that it stems from the five thousand year old Sumerian character dingir, though this hypothesis seems to only be based on visual appearance. When toning down expletives, asterisks are used to replace letters. For example, the word'fuck' might become'f**k','f*ck' or even'****'. Vowels tend to be censored with an asterisk more than consonants, but the intelligibility of censored profanities with multiple syllables such as b*ll*cks or uncommon ones is higher if put in context with surrounding text. In colloquial usage, an asterisk is used to indicate that a record is somehow tainted by circumstances, which are putatively explained in a footnote referenced by the asterisk; the usage of the term in sports arose after the 1961 baseball season in which Roger Maris of the New York Yankees broke Babe Ruth's 34-year-old single-season home run record. Because Ruth had amassed 60 home runs in a season with only 154 games, compared to Maris's 61 over 162 games, baseball commissioner Ford Frick announced that Maris's accomplishment would be recorded in the record books with an explanation.
In fact, Major League Baseball had no official record book at the time, but the stigma remained with Maris for many years, the concept of a real or figurative asterisk denoting less-than-official records has become used in sports and other competitive endeavors. A 2001 TV movie about Maris's record-breaking season was called 61* in reference to the controversy; the controversy over season length in relation to home run records had somewhat subsided by the time Hank Aaron broke Ruth's career home run record in 1974. Maris's single season mark was broken in 1998 by Mark McGwire and Sammy Sosa, who both broke it in under 154 games. McGwire's record of 70 home runs was eclipsed by Barry Bonds, who set the current mark of 73 home runs in the 2001 season. However, these players' accomplishments were soon questioned after evidence surfaced suggesting all three might have been taking advantage of MLB's then-lax policies related to the use of performance-enhancing drugs. Fans were critical of Bonds and invoked the asterisk notion during the 2007 season, as he approached and broke Hank Aaron's career home run record.
Opposing fans would hold up signs bearing asterisks whenever Bonds came up to bat. After Bonds hit his record-breaking 756th home run on August 7, 2007, fashion designer and entrepreneur Marc Ecko purchased the home run ball from the fan who caught it, ran a poll on his website to determine its fate. On September 26, Ecko revealed on NBC's Today show that the ball will be branded with an asterisk and donated to the Baseball Hall of Fame; the ball, marked with a die-cut asterisk, was delivered to the hall on July 2, 2008 after Marc Ecko unconditionally donated the artifact rather than loaning it to the hall as intended. In recent years, the asterisk has come into use on baseball scorecards to denote a "great defensive play." By the end of the first decade of the 21st century, the association of baseball and its records with doping had become so notorious that the term "asterisk" had become associated with doping in sport. In February 2011 the United States Olympic Committee and the Ad Council launched an anti-steroid campaign called "Play Asterisk Free" aimed at teens.
The campaign, whose logo uses a heavy asterisk, first launched in 2008 under the name Don't Be An Asterisk. In cricket, it signifies a total number of runs scored by a batsman without losing his wicket. Where only the scores of the two batsmen that are in are being shown, an asterisk following a batsman's score indicates that he is due to face the next ball to be delivered; when written before a player's name on a scorecard, it indicates the captain of the team. It is used on television when giving a career statistic during a match. For example, 47 * in a number of matches column means. In computer science, the asterisk is used in regular expressions to denote zero or more repetitions of a pattern. In the Unified Modeling Language, the asterisk is used to denote zero to many classes. In some command line interfaces, such as the Unix shell and Microso