Computer keybooard

Computer keyboard

In computing, a computer keyboard is a typewriter-style device[1] 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 (buttons) typically have characters engraved or printed on them,[2] and each press of a key typically corresponds to a single written symbol. However, producing some symbols may require pressing and holding several keys simultaneously or in sequence.[3] While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or execute computer commands.

In 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' Control-Alt-Delete combination, which brings up the system security options screens. A command-line interface is a type of user interface navigated entirely 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 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, teleprinter-like devices were used to simultaneously type and transmit stock market text data from the keyboard across telegraph lines to stock ticker machines to be immediately copied and displayed onto ticker tape.^[4] 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.^[5]

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 ENIACcomputer incorporated a keypunch device as both the input and paper-based 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.^[6]

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.^[7] However, keyboards remain central to human-computer interaction to the present, even 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, 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.Many keyboards are wireless, communicating with the computer via Bluetooth or an RF receiver.

Wired keyboards connect to the motherboard via a USB cable, using the USB Type A connector. Older keyboards connect via a PS/2 connection. Keyboards on laptops are of course integrated, but technically would be considered "wired" since that's how they are connected to the computer. Both wireless and wired keyboards require a specific device driver in order to be used with the computer. Drivers for standard, non-advanced keyboards usually don't need to be downloaded because they're already included in the operating system.

Tablets, phones, and other computers with touch interfaces often don't include physical keyboards. However, most do have USB receptacles or wireless technologies which allow external keyboards to be attached.

Like tablets, most modern mobile phones utilize on-screen keyboards to maximize the screen size; the keyboard can be used when needed but then that same screen space can be used for other things like watching videos. If the phone does have a keyboard, it's sometimes a slide-out, hidden keyboard that rests behind the screen. This both maximizes available screen space as well as allows for a familiar physical keyboard.

Laptops and netbooks have integrated keyboards but, like tablets, can have external keyboards attached via USB.

There are several legends around the development of the QWERTY keyboard layout, which was patented by Sholes and his partner James Densmore in 1878 and is still the most popular keyboard layout on devices of all types in the English speaking world. The most compelling is that Sholes developed the layout to overcome the physical limitations of machine technology at the time. Early typists pressed a key which would, in turn, push a metal hammer that would rise up in an arc, strike an inked ribbon making a mark on a paper and then return to its original position. Separating common pairs of letters minimized the jamming of the mechanism.

As the machine technology improved, other keyboard alignments were invented that claimed to be more efficient, such as the Dvorak keyboard patented in 1936. Although there are dedicated Dvorak users today, they remain a tiny minority compared to those who continue to use the original QWERTY layout. That's been attributed to the QWERTY keyboard being "efficient enough" and "familiar enough" to hinder the commercial viability of competitors.

Адрес публикации: https://www.prodlenka.org/metodicheskie-razrabotki/325313-computer-keybooard