In most languages except English, additional letters some with diacritics are required and some are present as standard on each national keyboard, as appropriate for its national language. These keyboards have another modified key, labelled AltGr alternative graphic , to the right of the space-bar. US keyboards just have a second Alt key in this position.
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These third-level and fourth-level symbols may be engraved on the right half of the key top, or they may be unmarked. Cyrillic alphabet and Greek alphabet keyboards have similar arrangements. Macs have a Ctrl key for compatibility with programs that expect a more traditional keyboard layout.
The key can generally be used to produce a secondary mouse click as well. There is also a Fn key on modern Mac keyboards, which is used for switching between use of the F1 , F2 , etc. Fn key can be also found on smaller Windows and Linux laptops and tablets, where it serves a similar purpose.
Some early keyboards experimented with using large numbers of modifier keys. This allowed the user to type over possible characters by playing suitable "chords" with many modifier keys pressed simultaneously. A dead key is a special kind of a modifier key that, instead of being held while another key is struck, is pressed and released before the other key. The dead key does not generate a character by itself, but it modifies the character generated by the key struck immediately after, typically making it possible to type a letter with a specific diacritic.
In some systems, there is no indication to the user that a dead key has been struck, so the key appears dead, but in some text-entry systems the diacritical mark is displayed along with an indication that the system is waiting for another keystroke: either the base character to be marked, an additional diacritical mark, or Space bar to produce the diacritical mark in isolation. Compared with the secondary-shift modifier key, the dead-key approach may be a little more complicated, but it allows more additional letters.
Using AltGr, only one or if used simultaneously with the normal shift key two additional letters with each key, whereas using a dead key, a specific diacritic can be attached to a range of different base letters. A Compose key can be characterized as a generic dead key that may in some systems be available instead of or in addition to the more specific dead keys. It allows access to a wide range of predefined extra characters by interpreting a whole sequence of keystrokes following it.
For example, striking Compose followed by ' apostrophe and then A results in á a with acute accent , Compose followed by A and then E results in æ ae ligature , and Compose followed by O and then C results in © circled c , copyright symbol. The Compose key is supported by the X Window System used by most Unix-like operating systems , including most Linux distributions.
Some keyboards have a key labeled "Compose", but any key can be configured to serve this function. This can be emulated in Windows with third party programs, for example Wincompose. 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.
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. Another common application today of the Esc key is to trigger the Stop button in many web browsers.
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ESC was part of the standard keyboard of the Teletype Model 33 introduced in and used with many early minicomputers. 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.
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: 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. It is used to launch a context menu with the keyboard rather than with the usual right mouse button.
The key's 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. The Windows key opens the 'Start' applications menu. Keyboard layouts have evolved over time, usually alongside major technology changes. Particularly influential have been: the Sholes and Glidden typewriter , also known as Remington No. Within a community, keyboard layout is generally quite stable, due to the high training cost of touch-typing, and the resulting network effect of having a standard layout and high switching cost of retraining, and the suboptimal QWERTY layout is a case study in switching costs.
Nevertheless, significant market forces can result in changes as in Turkish adoption of QWERTY , and non-core keys are more prone to change, as they are less frequently used and less subject to the lock-in of touch-typing. The main, alphanumeric portion is typically stable, while symbol keys and shifted key values change somewhat, modifier keys more so, and function keys most of all: QWERTY dates to the No.
The earliest mechanical keyboards were used in musical instruments to play particular notes. With the advent of the printing telegraph , a keyboard was needed to select characters. Some of the earliest printing telegraph machines used a layout similar to a piano keyboard. In countries using the Latin script , the center, alphanumeric portion of the modern keyboard is most often based on the QWERTY design by Christopher Sholes , who laid out the keys in such a way that common two-letter combinations were placed on opposite sides of the keyboard so that his mechanical keyboard would not jam, and laid out the keys in rows offset horizontally from each other by three-eighths, three-sixteenths, and three-eighths inches to provide room for the levers.
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Although it has been demonstrated that the QWERTY layout is not the most efficient layout for typing,  it remains the standard. Sholes chose the size of the keys to be on three-quarter [¾, or 0. On a manual typewriter, the operator could press the key down with a lighter touch for such characters as the period or comma, which did not occupy as much area on the paper. Since an electric typewriter supplied the force to the typebar itself after the typist merely touched the key, the typewriter itself had to be designed to supply different force for different characters. To simplify this, the most common layout for electric typewriters in the United States differed from that for the one most common on manual typewriters.
Single-quote and double-quote, instead of being above the keys for the digits 2 and 8 respectively, were placed together on a key of their own. The underscore, another light character, replaced the asterisk above the hyphen. The ASCII communications code was designed so that characters on a mechanical teletypewriter keyboard could be laid out in a manner somewhat resembling that of a manual typewriter. This was imperfect, as some shifted special characters were moved one key to the left, as the number zero, although on the right, was low in code sequence.
Later, when computer terminals were designed from less expensive electronic components, it wasn't necessary to have any bits in common between the shifted and unshifted characters on a given key.
This eventually led to standards being adopted for the "bit-pairing" and "typewriter-pairing" forms of keyboards for computer terminals. The typewriter-pairing standard came under reconsideration, on the basis that typewriters have many different keyboard arrangements. Newer keyboards may incorporate even further additions, such as Internet access World Wide Web navigation keys and multimedia access to media players buttons.
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As noted before, the layout of a keyboard may refer to its physical arrangement of keys , visual physical labeling of keys , or functional software response to a key press or release layout. Physical layouts only address tangible differences among keyboards. When a key is pressed, the keyboard does not send a message such as the A-key is depressed but rather the left-most main key of the home row is depressed.
Technically, each key has an internal reference number, the scan code, and these numbers are what is sent to the computer when a key is pressed or released. The keyboard and the computer each have no information about what is marked on that key, and it could equally well be the letter A or the digit 9. Historically, the user of the computer was requested to identify the functional layout of the keyboard when installing or customizing the operating system ; modern USB keyboards have plug'n'play , so that they communicate their visual layout to the OS when connected but the user continues to have the ability to reset this at will.
In fact, the physical layouts referred such as "ISO" and "ANSI" comply to the primary recommendations in the named standards, while each of these standards in fact also allows the other. Keyboard layout in this sense may refer either to this broad categorization or to finer distinctions within these categories.
The visual layout includes the symbols printed on the physical keycaps. Visual layouts vary by language, country, and user preference, and any one physical and functional layout can be employed with a number of different visual layouts. For example, the "ISO" keyboard layout is used throughout Europe, but typical French, German, and UK variants of physically identical keyboards appear different because they bear different legends on their keys. Even blank keyboards — with no legends — are sometimes used to learn typing skills or by user preference.
Some users choose to attach custom labels on top of their keycaps. This can be e.
The functional layout of the keyboard refers to the mapping between the physical keys, such as the A key, and software events, such as the letter "A" appearing on the screen. Usually the functional layout is set to match the visual layout of the keyboard being used, so that pressing a key will produce the expected result, corresponding to the legends on the keyboard. However, most operating systems have software that allow the user to easily switch between functional layouts, such as the language bar in Microsoft Windows. For example, a user with a Swedish keyboard who wishes to type more easily in German may switch to a functional layout intended for German — without regard to key markings — just as a Dvorak touch typist may choose a Dvorak layout regardless of the visual layout of the keyboard used.