Keyboard (computing)

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Image:Qwerty.svg
The 104-key PC US English QWERTY keyboard layout evolved from the standard typewriter keyboard with extra keys special to computing.
Image:KB United States Dvorak.svg
The Dvorak Simplified Keyboard layout, shown, arranges keys so that frequently-used keys are easiest to press. The typical QWERTY layout was designed to meet the technical limitations of mechanical typewriters rather than for ergonomics.
Image:Hebkeyboard.JPG
The standard Hebrew keyboard, shown here, lets the user type in both Hebrew and the Latin alphabet.

In computing, a keyboard is a peripheral partially modeled after the typewriter keyboard.

Physically, keyboards are an arrangement of rectangular buttons, or keys. Keyboards typically have characters engraved or printed on the keys; in most cases, each press of a key corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence; other keys do not produce any symbol, but instead affect the operation of the computer or the keyboard itself. See input method editor.

A majority of all keyboard keys produce letters, numbers or signs (characters) that are appropriate for the operator's language. Other keys can produce actions when pressed, and other actions are available by the simultaneous pressing of more than one action key.

Contents

[edit] Designs

Image:Foldable keyboard.jpg
Most keyboards are rigid, but this foldable keyboard demonstrates one of many variations from the usual.

There exist a large number of different arrangements of symbols on keys. These different keyboard layouts arise mainly because different people need easy access to different symbols; typically, this is because they are writing in different languages, but specialized keyboard layouts for mathematics, accounting, and computer programming also exist.

Most of the more common keyboard layouts (QWERTY-based and similar) were designed in the era of the mechanical typewriters, so their ergonomics had to be slightly compromised in order to tackle some of the technical limitations of the typewriters. The letters were attached to levers that needed to move freely; jamming would result if commonly-used letters were placed too close to one another. The QWERTY layout is an invention of Christopher Sholes. With the advent of modern electronics, this is no longer an issue. QWERTY layouts and their brethren had been a de facto standard for decades prior to the introduction of the very first computer keyboard, and were primarily adopted for electronic keyboards for this reason. Alternative layouts do exist, the best known of which are the Dvorak and more recently Colemak layouts; however, these are not in widespread use.

The number of keys on a keyboard varies from the standard of 101 keys introduced in the late 1980s to the 104-key windows keyboards and all the way up to 130 keys or more, with many of the additional keys being symbol-less programmable keys that can simulate multiple functions such as starting a web browser or e-mail client. There also were "Internet keyboards," sold in the late 1990s, that replaced the function keys with pre-programmed internet shortcuts. Pressing the shortcut keys would launch a browser to go to that website.

[edit] Connection types

There are several different ways of connecting a keyboard which have evolved over the years. These include the standard AT (DIN-5) connector commonly found on pre-80486 motherboards, which was eventually replaced by the PS/2 and USB connection. Prior to the iMac line of systems, Apple Computer used ADB, a proprietary system, for its keyboard connector.

[edit] Wireless types

Wireless keyboards have become popular for their increased user freedom. However, wireless keyboards need batteries to work, and may pose a security problem due to the risk of eavesdropping.[1]

A wireless keyboard often includes a required combination transmitter and receiver unit that attaches to the computer's keyboard port (see Connection types above). 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.

[edit] Buckling spring vs. dome switch

Keys on older IBM keyboards were made with a "buckling spring" mechanism, in which a coil spring under the key buckles under pressure from the user's finger, pressing a rubber dome, whose inside is coated with conductive graphite, which connects two leads below, completing a circuit. This produces a clicking sound, and a "positive" feel of feedback, so that the typist knows when the key is fully pressed. Keys on most modern keyboards are made with a so-called "dome switch" mechanism, without the buckling spring. Many typists prefer the buckling spring board, which is still manufactured.[2][3]

[edit] Alternatives

Image:Multimediakb.jpg
A multimedia keyboard like this one offers special keys for accessing music, web, and other oft-used programs.

A standard keyboard is physically quite large, as each key must remain large enough to be easily pressed by fingers. Other types of keyboards have been proposed for small portable equipment where a standard keyboard is too large. One way to reduce the size of the keyboard is to reduce the number of keys and use chording keyer, i.e. pressing several keys simultaneously. For example, the GKOS keyboard has been designed for small wireless devices. Other two-handed alternatives more akin to a game controller, such as the AlphaGrip, are also used as a way to input data and text.

Another way to reduce the size of a keyboard is to use smaller buttons and pack them closer together. Such keyboards, often called a "thumbboard" (thumbing) are used in some personal digital assistants such as the Treo and BlackBerry and some Ultra-Mobile PCs such as the OQO.

A relatively new type of keyboard, the I-Tech Virtual Laser Keyboard, works by projecting an image of a full size keyboard onto a surface. Sensors in the projection unit identify which key is being "pressed" and relay the signals to a computer or PDA.

It is possible to limit or eliminate the use of computer keyboards with the introduction of speech recognition and optical character recognition. Speech recognition however, while is already implemented in various commercial products, is far away from the horizons where it can fully replace typing and represents a very difficult scientific research task being too dependent on voice characteristics.

Some keyboard layouts are specifically designed for speed. The most common is the Dvorak layout; more recently, layouts such as Colemak have been developed to improve on Dvorak and to be easier to learn for existing QWERTY users. The fastest keyboard so far is the stenotype -- some people who use a stenotype type faster than 300 words per minute[citation needed].

[edit] Standards

In principle, computer keyboard designs are governed by the ISO/IEC 9995 international standard.

[edit] Historical

While the IBM PC keyboard was hardly the first electronic keyboard, it does merit particular mention, if only for its ubiquity. The original IBM PC/XT had 83 keys, the AT keyboard had 84 (adding a SysRq key and separating keys into sections, also changing the communication protocol), next the "Enhanced" 101 keys (duplicating the cursor movement keys from the numeric pad, adding the function key row along the top and increasing their number from 10 to 12, other minor changes, and of course the often maligned control-key/caps-lock switch. The above-mentioned 104 keys were obtained by adding three "windows" keys. The internationally common 102/105 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). [4]

[edit] Usage

Image:OnBoardKeyboard.png
An on-screen keyboard controlled with the mouse can be used by users with limited mobility.

In normal usage, the keyboard is used to type text into a word processor, text editor, or any other textbox.

In modern computers the interpretation of keypresses is generally left to the software. Modern keyboards distinguish each physical key from every other and report all keypresses to the controlling software. This flexibility is not often taken advantage of and it usually does not matter, for example, whether the left or right shift key is held down in conjunction with another character, even though they are coded as completely separate keys.

[edit] Keystroke

Image:QWERTY keyboard.jpg
Laptop keyboards such as on this Sony Vaio have a shorter travel distance for the keystroke and usually have a reduced set of keys to make the keyboard (and laptop) more convenient to carry.

A keystroke refers to the simple act of pressing a button on a keyboard that is connected to some form of digital computer. Nefarious programs may log keystrokes and thereby capture such sensitive information as operating system passwords and credit card numbers.

[edit] Commands

A keyboard is also used to type commands in a computer. One famous example on the PC is the Control-Alt-Delete combination. On most versions of Microsoft Windows, this command brings up a window (such as the Task Manager on Windows NT based versions of Windows) which allows users to manage currently-running processes, shut down the machine, and other functions. Under Linux, MS-DOS and some older versions of Windows, the command performs either a 'cold' or 'warm' reboot.

[edit] Games

A keyboard is one of the primary methods of control in computer games. For instance, the arrow keys or a group of letters resembling the pattern of the arrow keys, like WASD, can be used for movement of a game character. In many games, keys can be configured to the user's preferences. Alphabet keys are also sometimes used to perform actions starting with that letter. (e.g. pressing j to jump, r to reload or c to crouch).

[edit] Buying considerations

Some low-quality keyboards suffer problems when multiple keys are pressed in quick succession; some types of keyboard circuitry will register a maximum number of keys at one time. This is undesirable for games (designed for multiple keypresses, e.g. casting a spell while holding down keys to run) and undesirable for extremely fast typing (hitting new keys before the fingers can release previous keys). A common side effect of this shortcoming is called "phantom key blocking": on some keyboards, pressing three keys simultaneously sometimes resulted in a 4th keypress being registered. Modern keyboards prevent this from happening by blocking the 3rd key in certain key combinations, but while this prevents phantom input, it also means that when two keys are depressed simultaneously, many of the other keys on the keyboard will not respond until one of the two depressed keys is lifted. With better keyboards designs, this seldom happens in office programs, but it remains a problem in games even on expensive keyboards, due to wildly different and/or configurable key/command layouts in different games.

[edit] Safety Precautions

Some experts believe that the use of any keyboard may cause serious injury to hands, wrists, arms, neck or back. Ways to reduce the risks of injuries can be done by:

  1. Take frequent short breaks. Get up and walk around at least a couple of times every hour.
  2. Vary your tasks throughout the day.
  3. Keep your shoulders relaxed with your elbows at your side. Postition your keyboard and mouse so you don't have to reach.
  4. Adjust your chair and keyboard so your wrists are straight.
  5. Avoid resting your wrists on sharp edges. If you use a wrist or palm rest don't use it while typing.

[edit] How it works

The following briefly describes a "dome-switch" keyboard (sometimes incorrectly referred to as a membrane keyboard), the most common type in use today:

  1. When a key is pressed, it pushes down on a rubber dome sitting beneath the key. A conductive contact on the underside of the dome touches (and hence connects) a pair of conductive lines on the circuit below.
  2. This bridges the gap between them and allows electric current to flow (the open circuit is closed).
  3. A scanning signal is emitted by the chip along the pairs of lines to all the keys. When the signal in one pair becomes different, the chip generates a "make code" corresponding to the key connected to that pair of lines.
  4. The code generated is sent to the computer either via a keyboard cable (using on-off electrical pulses to represent bits) or over a wireless connection. It may be repeated.
  5. A chip inside the computer receives the signal bits and decodes them into the appropriate keypress. The computer then decides what to do on the basis of the key pressed (e.g. display a character on the screen, or perform some action).
  6. When the key is released, a break code (different than the make code) is sent to indicate the key is no longer pressed. If the break code is missed (e.g. due to a keyboard switch) it is possible for the keyboard controller to believe the key is pressed down when it is not, which is why pressing then releasing the key again will release the key (since another break code is sent).

Other types of keyboards function in a similar manner, the main differences being how the individual key-switches work. For more on this subject refer to the article on keyboard technology.

Certain key presses are special, namely Ctrl-Alt-Delete and SysRq, but what makes them special is a function of software. In the PC architecture, the keyboard controller (the component in the computer that receives the make and break codes) sends the computer's CPU a hardware interrupt whenever a key is pressed or released. The CPU's interrupt routine which handles these interrupts usually just places the key's code in a queue, to be handled later by other code when it gets around to it, then returns to whatever the computer was doing before. The special keys cause the interrupt routine to take a different "emergency" exit instead. This more trusted route is much harder to intercept.

[edit] Customization

Sometimes, it is desired to customize the layout of a keyboard or remap the keys. Keyboard remapping is supported at a driver level configurable within the operating system, or as add-ons to the existing programs.

For Windows, Microsoft provides a free downloadable tool called Microsoft Keyboard Layout Creator, and there are several other software programs for this purpose:

Under systems running X11 (e.g. GNU/Linux) this can be done with xmodmap.

[edit] Keys on a computer keyboard

[edit] See also

Image:Commons-logo.svg
Wikimedia Commons has media related to:
Keyboard

References regarding problems with keypresses in short succession:

[edit] References

  1. ^ Brandt, Andrew. "Privacy Watch: Wireless Keyboards That Blab", PC World, 2003-01-29. 
  2. ^ A Passion for the Keys: Particular About What You Type On? Relax -- You're Not Alone. LOOSE WIRE, By JEREMY WAGSTAFF, Wall Street Journal, November 23, 2007
  3. ^ Dan's Data Review: IBM 42H1292 and 1391401 keyboards, Review date: 15 August 1999, updated 13-Nov-2007]
  4. ^ "Standard Keyboard Layouts". 

[edit] External links


IBM/Wintel Keyboard:
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Esc F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 PtSc ScLk Brk
<imagemap>

Image:KB United States.svg|450px desc none

  1. # Row are 60 pixel tall in reference to the unsized original # rect left top right bottom [[link]] #
  2. Top row shift

rect 0 0 60 30 Tilde rect 60 0 120 30 Exclamation mark rect 120 0 180 30 At sign rect 180 0 240 30 Number sign rect 240 0 300 30 Dollar sign rect 300 0 360 30 Percent sign rect 360 0 420 30 Caret rect 420 0 480 30 Ampersand rect 480 0 540 30 Asterisk rect 540 0 600 30 Bracket rect 600 0 660 30 Bracket rect 660 0 720 30 Underscore rect 720 0 780 30 Plus and minus signs rect 780 0 900 30 Backspace

  1. Top row

rect 0 0 60 60 Grave accent rect 60 0 120 60 1 (number) rect 120 0 180 60 2 (number) rect 180 0 240 60 3 (number) rect 240 0 300 60 4 (number) rect 300 0 360 60 5 (number) rect 360 0 420 60 6 (number) rect 420 0 480 60 7 (number) rect 480 0 540 60 8 (number) rect 540 0 600 60 9 (number) rect 600 0 660 60 0 (number) rect 660 0 720 60 Hyphen rect 720 0 780 60 Equals sign rect 780 0 900 60 Backspace

  1. Second row shift

rect 0 61 90 90 Tab key rect 90 61 150 90 Q rect 150 61 210 90 W rect 210 61 270 90 E rect 270 61 330 90 R rect 330 61 390 90 T rect 390 61 450 90 Y rect 450 61 510 90 U rect 510 61 570 90 I rect 570 61 630 90 O rect 630 61 690 90 P rect 690 61 750 90 Bracket rect 750 61 810 90 Bracket rect 810 61 900 90 Vertical bar

  1. Second row

rect 0 61 90 120 Tab key rect 90 61 150 120 Q rect 150 61 210 120 W rect 210 61 270 120 E rect 270 61 330 120 R rect 330 61 390 120 T rect 390 61 450 120 Y rect 450 61 510 120 U rect 510 61 570 120 I rect 570 61 630 120 O rect 630 61 690 120 P rect 690 61 750 120 Bracket rect 750 61 810 120 Bracket rect 810 61 900 120 Backslash

  1. Third row shift

rect 0 121 105 150 Caps lock rect 105 121 165 150 A rect 165 121 225 150 S rect 225 121 285 150 D rect 285 121 345 150 F rect 345 121 405 150 G rect 405 121 465 150 H rect 465 121 525 150 J rect 525 121 585 150 K rect 585 121 645 150 L rect 645 121 705 150 Colon (punctuation) rect 705 121 765 150 Quotation mark rect 765 121 900 150 Enter key

  1. Third row

rect 0 121 105 180 Caps lock rect 105 121 165 180 A rect 165 121 225 180 S rect 225 121 285 180 D rect 285 121 345 180 F rect 345 121 405 180 G rect 405 121 465 180 H rect 465 121 525 180 J rect 525 121 585 180 K rect 585 121 645 180 L rect 645 121 705 180 Semicolon rect 705 121 765 180 Apostrophe rect 765 121 900 180 Enter key

  1. Fourth row shift

rect 0 181 135 210 Shift key rect 135 181 195 210 Z rect 195 181 255 210 X rect 255 181 315 210 C rect 315 181 375 210 V rect 375 181 435 210 B rect 435 181 495 210 N rect 495 181 555 210 M rect 555 181 615 210 Bracket rect 615 181 675 210 Bracket rect 675 181 735 210 Question mark rect 735 181 900 210 Shift key

  1. Fourth row

rect 0 181 135 240 Shift key rect 135 181 195 240 Z rect 195 181 255 240 X rect 255 181 315 240 C rect 315 181 375 240 V rect 375 181 435 240 B rect 435 181 495 240 N rect 495 181 555 240 M rect 555 181 615 240 Comma (punctuation) rect 615 181 675 240 Full stop rect 675 181 735 240 Slash (punctuation) rect 735 181 900 240 Shift key

  1. Bottom row

rect 0 241 90 300 Control key rect 90 241 150 300 Windows key rect 150 241 240 300 Alt key rect 240 241 600 300 Space bar rect 600 241 690 300 AltGr key rect 690 241 750 300 Windows key rect 750 241 810 300 Menu key rect 810 241 900 300 Control key

</imagemap>

Ins Home PgUp Num / * -
Del End PgDn 7 8 9 +
4 5 6
↑ 1 2 3 Ent
← ↓ → 0 .
v • d • e
Keyboard keys
Dead keysCompose
Modifier keysControl · Shift · Alt/Option (Apple) · AltGr · Command/Meta (Apple/MIT/Sun keyboards) · Windows/Super · Fn (compact keyboards)
Lock keysScroll lock · Num lock · Caps lock
NavigationArrow · Page Up/Page Down  · Home/End
EditingReturn/Enter · Backspace · Insert · Delete · Tab · Space bar
Misc.System request/Print screen · Break/Pause · Escape · Menu · Numeric keypad · Function · Power management (Power, Sleep, Wake) · Language input · Any key
af:Sleutelbord

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