User:JMF/Computer keyboard/Sandbox

This article is a brief overview of computer keyboards. For a detailed discussion of the hardware aspects, see Keyboard technology. For the user interface expressed in software, see Keyboard layout

Not to be confused with keyboard computer.

Typing on a computer keyboard

A computer keyboard is a text entry interface that uses an arrangement of buttons or keys that act as electronic switches. Such keyboards broadly follow typewriter keyboard conventions, though substantially evolved from those historic designs.

Keyboard keys (buttons) typically have a set of characters engraved or printed on them, and each press of a key (or combination of keys) typically corresponds to a single written symbol or or other interrupt request. While most keyboard keys produce letters, numbers or symbols (characters), other keys or simultaneous key presses can prompt the computer to execute system commands, such as such as the Control-Alt-Delete combination used with Microsoft Windows. In a modern computer, the interpretation of key presses is generally left to the software: the information sent to the computer, the scan code, tells it only which key (or keys) on which row and column, was pressed or released. Consequently, the effect of pressing a particular key is determined by the computer's operating system, independently of (and potentially over-riding) the symbols engraved on the keys.

History

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. 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 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, 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, even as mobile personal computing devices such as smartphones and tablets adapt the keyboard as an optional virtual, touchscreen-based means of data entry.

Keyboard technology: the hardware

Keyboard keys

This section is an excerpt from Keyboard technology.[edit]

Keyboard construction of a typical notebook computer keyboard, in four layers.

The technology of computer keyboards includes many elements. Many different keyboard technologies have been developed for consumer demands and optimized for industrial applications. The standard full-size (100%) computer alphanumeric keyboard typically uses 101 to 105 keys; keyboards integrated in laptop computers are typically less comprehensive.

Virtual keyboards, which are mostly accessed via a touchscreen interface, have no physical switches and provide artificial audio and haptic feedback instead. This variety of keyboard can prove useful, as it is not limited by the rigid nature of physical computer keyboards.

The majority of modern keyboards include a control processor and indicator lights to provide feedback to the user (and to the central processor) about what state the keyboard is in. Plug-and-play technology means that its "out of the box" layout can be notified to the system, making the keyboard immediately ready to use without the need for further configuration, unless the user so desires. This also enables manufacture of generic keyboards for a variety of language markets, that differ only in the symbols engraved on the keytops.

Keyboard management: the software

Software control of the keyboard and its interface with applications is delivered by the keyboard device driver. A system configuration is used to declare the input method being used, the default language in use and the symbolic meaning to attach to each scan-code.

Keyboard layouts

This section is an excerpt from Keyboard layout.[edit]

The 104-key US QWERTY layout

A keyboard layout is any specific physical, visual, or functional arrangement of the keys, legends, or key-meaning associations (respectively) of a computer keyboard, mobile phone, or other computer-controlled typographic keyboard.

Physical layout is the actual positioning of keys on a keyboard. Visual layout is the arrangement of the legends (labels, markings, engravings) that appear on those keys. Functional layout is the arrangement of the key-meaning association or keyboard mapping, determined in software, of all the keys of a keyboard; it is this (rather than the legends) that determines the actual response to a key press.

Modern computer keyboards are designed to send a scancode to the operating system (OS) when a key is pressed or released: this code reports only the key's row and column, not the specific character engraved on that key. The OS converts the scancode into a specific binary character code using a "scancode to character" conversion table, called the keyboard mapping table. This means that a physical keyboard may be dynamically mapped to any layout without switching hardware components—merely by changing the software that interprets the keystrokes. Often, a user can change keyboard mapping in system settings. In addition, software may be available to modify or extend keyboard functionality. Thus the symbol shown on the physical key-top need not be the same as appears on the screen or goes into a document being typed. Some settings enable the user to type supplementary symbols that are not engraved on the keys used to invoke them. Modern USB keyboards are plug-and-play; they communicate their (default) visual layout to the OS when connected (though the user is still able to reset this at will).

See also

• Input device – Device that provides data and signals to a computer