Computer_keyboard

"Keyboard" redirects here. For other uses, see Keyboard (disambiguation).

The 104-key PC US English QWERTY keyboard layout evolved from the standard typewriter keyboard with extra keys special to computing.

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. Specifically, mechanical typewriters would jam frequently due to high typing rates on faster/more ergonomic layouts. Dvorak also encourages balanced muscle development and frequent load shifting to reduce muscle fatigue when typing common english.

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.

The Microwriter MW4 (circa 1980), as used by Douglas Adams, features a chording keyboard

Physically, a keyboard is an arrangement of rectangular buttons, or keys. A keyboard typically has 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 1 Designs 1.1 Keyboard layouts (QWERTY, Dvorak, et al) 1.2 Connection types 1.3 Wireless types 1.4 Buckling spring vs. dome switch 1.5 Alternatives to the "regular" keyboard 1.5.1 Smaller keyboards 1.5.2 Keyboards with extra keys 1.5.2.1 Multimedia keyboards 1.5.2.2 Gaming keyboards 1.5.3 Virtual keyboards 1.5.4 Keyboard layout alternatives to QWERTY 1.5.5 Input by alternate text input devices 1.5.5.1 OCR 1.5.5.2 Speech recognition 1.5.5.3 Pointing-device text input 1.6 Standards 1.7 Historical 2 Usage 2.1 Keystroke 2.2 Commands 2.3 Games 2.4 Buying considerations 2.4.1 Rollover problems 2.4.2 Capital investment versus later costs 2.5 Safety Precautions 3 How it works 4 Customization 5 Keys on a computer keyboard 6 See also 7 References 8 External links

Designs

Keyboard layouts (QWERTY, Dvorak, et al)

Main article: Keyboard layout

There exists 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; because jamming would result if commonly-used letters were placed too close to one another Christopher Sholes invented the QWERTY layout. However, 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.

Connection types

This photograph shows a QWERTY keyboard dismantled, with all of the keys properly removed, during the cleaning process.

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.

Wireless types

Wireless keyboards have become popular for their increased user freedom. However, a wireless keyboard needs batteries to work and may pose a security problem due to the risk of eavesdropping.Brandt, Andrew. "Privacy Watch: Wireless Keyboards That Blab", PC World, 2003-01-29. 

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. With Bluetooth, the tranceiver may be build in to the computer.

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.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, 2007Dan\'s Data Review: IBM 42H1292 and 1391401 keyboards, Review date: 15 August 1999, updated 13-Nov-2007]

Alternatives to the "regular" keyboard

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

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

Smaller keyboards

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.

Keyboards with extra keys

Multimedia keyboards

Multimedia keyboards offer special keys for accessing music, web, and other oft-used programs. They also usually have other convenient controls, such as a mute button, volume buttons or knob, and standby (sleep) button.

Gaming keyboards

Some gaming keyboards offer extra function keys which can be programmed with keystroke macros. For example, ctrl+shift+y could be a keystroke that is frequently used in a certain computer game. But it is a physically awkward (or, at least, annoying) combination for the hands to reach for repeatedly. It may be very useful to assign that keystroke combination to one function key. Some keyboards (Such as the Logitech G11 or G15) have a keypad full of "G keys" to the left of the QWERTY keyboard for this purpose. The keystroke macros can be reprogrammed at will.

The development of these keyboards was spurred by gaming, but the concept can also be very convenient in non-gaming applications, such as office work. Any keystroke combination that is awkward or annoying but frequently needed can be replaced with a "G key". The meaning of the "G key" press can automatically change depending on which application has focus, thus extending the number of macros available given a certain limited number of G keys.

Virtual keyboards

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 personal digital assistant.

Keyboard layout alternatives to QWERTY

As explained above, the QWERTY layout was a legacy from mechanical typewriters. In contrast, 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]}.

v • d • e Keyboard layouts
QWERTY based	QWERTY  · AZERTY  · QWERTZ
Alternative layouts	Dvorak  · Colemak  · Maltron  · Svorak  · Plum
Non-Roman	Hebrew  · Urdu
For mobile devices	FITALY  · GKOS
Historical	Blickensderfer (DHIATENSOR)  · HCESAR

Input by alternate text input devices

It is possible to limit or eliminate the use of computer keyboards with the introduction of alternative methods not based in keystrokes, such as optical character recognition (OCR), speech recognition and pointing-device text input.

OCR

Optical character recognition (OCR) is preferable to rekeying for converting existing text that is already written down but not in machine-readable format (for example, a Linotype-composed book from the 1940s). In other words, to convert the text from an image to editable text (that is, a string of character codes), a person could re-type it, or a computer could look at the image and deduce what each character is. OCR technology has already reached an impressive state (for example, Google Book Search) and promises more for the future.

Speech recognition

Speech recognition converts speech into machine-readable text (that is, a string of character codes). The technology has already reached an impressive state and is already implemented in various commercial products. For certain uses (e.g., transcription of medical or legal dictation; journalism; writing essays or novels) it is starting to replace the keyboard; however, it does not threaten to replace keyboards entirely anytime soon. It can, however, interpret commands (for example, "close window" or "undo that") in addition to text. Therefore, it has theoretical potential to replace keyboards entirely (whereas OCR replaces them only for a certain kind of task).

Pointing-device text input

There is a class of hardware or software accessories enabling users to enter text efficiently using a pointing device, in contexts where using a physical keyboard would be inappropriate or impossible. These accessories typically present characters on a display, in a layout that provides fast access to the more frequently used characters or character combinations. Popular examples of this kind of input are Graffiti, Dasher and on-screen virtual keyboards.

Standards

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

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 came the "Enhanced" 101 keys (which duplicated the cursor movement keys from the numeric pad, added the function key row along the top and increased their number from 10 to 12, made other minor changes, and included an often-maligned control-key/caps-lock placement swap). 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)."Standard Keyboard Layouts". 

Usage

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 a modern computer the interpretation of keypresses is generally left to the software. A modern keyboard distinguishes 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.

Keystroke

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.

The term keystroke refers to the simple act of pressing a button on a keyboard that is connected to some form of digital computer. The term is also frequently used to mean a keystroke combination (several keys pressed at once, for example, ctrl+shift+spacebar) used as a keyboard shortcut (also known as a shortcut key or other names).

Nefarious programs may log keystrokes and thereby capture such sensitive information as operating system passwords and credit card numbers.

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.

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). As explained earlier, gaming keyboards can expedite awkward or frequently used keystroke combinations.

Buying considerations

Rollover problems

Some low-quality keyboards suffer problems with rollover (that is, 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.

Capital investment versus later costs

Computer input devices, including keyboards, are a good example where a bit more capital investment up front can more than pay for itself over time by reducing future costs. For example, buying an ergonomic keyboard (one with the QWERTY field divided into two sections angled away from each other) may cost $20 more up front, but if it keeps repetitive strain injury at a subclinical level rather than allowing it to progress to a level of clinical dysfunction, then it has paid for itself many times over by obviating future medical costs, user discomfort or annoyance, partial disability, etc. The same can be said of keyboards with programmable hot keys that obviate awkward keystroke combinations.

Safety Precautions

Some experts believe that the use of any keyboard may cause serious injury (that is, carpal tunnel syndrome or other repetitive strain 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. Position your keyboard and mouse so you do not 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 do not use it while typing.

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.

Customization

Sometimes it is helpful to customize the layout of a keyboard by remapping the keys. When you remap a key, you tell the computer a new meaning for the pressing of that key. 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:

• SharpKeys: free
• KeyTweak: free

Keys on a computer keyboard

A Space-cadet keyboard has many modifier keys.

• Modifier key
  • Control key
  • Shift key
  • Alt key / Option key (Macintosh)
  • AltGr key
  • Command key / Meta key (MIT computer keyboards)
  • Windows key
  • Fn key (compact keyboard layout)
• Dead key
  • Compose key
• Lock key
  • Scroll lock
  • Num lock
  • Caps lock
• Navigation keys
  • Arrow keys
  • Page scroll keys (Page up key / Page down key)
  • Home / End key
  • Edit keys
  • Return key / Enter key
  • Backspace
  • Insert key
  • Delete key
  • Tab key
• SysRq / Print screen
• Break / Pause key
• Escape key
• Menu key
• Space bar
• Numeric keypad
• Function key
• Language input keys (on Japanese/Korean keyboards)
  • Kanji key
  • Conversion key
  • Non-conversion key
  • Half-width/Full-width key
  • Hiragana/Katakana key
  • Alphanumeric key
  • Hancha key
  • Han/Yong key
• Power management keys
  • Power key
  • Sleep key
  • Wake key
• Internet keys:
  • Internet (web browser) key.
  • E-mail
• Multimedia keys:
  • Volume keys or wheel (+/-/mute).

See also

Wikimedia Commons has media related to:

Keyboard

• Ergonomics
• Repetitive strain injury
• Keyboard styles
  • Alphanumeric keyboard
  • Enhanced keyboard
    • AT keyboard
  • Velotype (chorded keyboard)
  • Virtual keyboard
  • Optimus Maximus keyboard
  • Das Keyboard (blank keyboard)

• "fixed split keyboard" and "adjustable split keyboard" with a larger gap between the "left hand keys" and the "right hand keys"
  • EZ-Reach (keyboard)
  • Microsoft Natural keyboard
  • Maltron keyboard
  • Kinesis keyboard
  • Datahand (featuring joystick-like buttons to reduce finger movement)

• Keyboard layout
  • Colemak
  • Dvorak keyboard
  • British and American keyboards

• Keyboard technology
  • Membrane keyboard
  • Chiclet keyboard
  • Buckling spring

• Apple Keyboard
• ASCII
• ASDF (sequence of letters)
• British and American keyboards
• Chinese input methods for computers
• Chord keyset
• F-Lock
• GKOS keyboard (chorded keyboard)
• IBM PC keyboard
• Lighted Program Function Keyboard
• Model M Keyboard
• Overlay keyboard
• Space-cadet keyboard
• Touch typing
• Typing
• Hunt and peck typing
• Home row
• Key jamming
• Rollover (key)
• QWERTY and accents
• Table of keyboard shortcuts
• Happy Hacking Keyboard
• FrogPad

References regarding problems with keypresses in short succession:

• http://forums.logitech.com/logitech/board/message?board.id=hardware&thread.id=991
• http://ask.metafilter.com/51940/Whats-a-brand-of-keyboard-that-allow-multiple-keys-to-be-pressed

References

External links

• Large searchable database of keyboard shortcuts at Keyxl.com
• OS X Keyboard Shortcuts
• Keyboard Help — Typing world language accent marks and other diacritics with your keyboard.

IBM/Windows keyboard (US layout) v • d • e
Esc		F1	F2	F3	F4		F5	F6	F7	F8		F9	F10	F11	F12		PtSc	ScLk	Brk
: image is invalid or non-existent																	Ins	Home	PgUp		Num	/	*	-
																	Del	End	PgDn		7	8	9	+
																					4	5	6
																		↑			1	2	3	Ent
																	←	↓	→		0		.

v • d • e Keyboard keys
Dead keys	Compose
Modifier keys	Control · Shift · Alt/Option (Apple) · AltGr · Command/Meta (Apple/MIT/Sun keyboards) · Windows/Super · Fn (compact keyboards)
Lock keys	Scroll lock · Num lock · Caps lock
Navigation	Arrow · Page Up/Page Down · Home/End
Editing	Return/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 · Macro key

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