- Great Painters
- Accounting
- Fundamentals of Law
- Marketing
- Shorthand
- Concept Cars
- Videogames
- The World of Sports

- Blogs
- Free Software
- Google
- My Computer

- PHP Language and Applications
- Wikipedia
- Windows Vista

- Education
- Masterpieces of English Literature
- American English

- English Dictionaries
- The English Language

- Medical Emergencies
- The Theory of Memory
- The Beatles
- Dances
- Microphones
- Musical Notation
- Music Instruments
- Batteries
- Nanotechnology
- Cosmetics
- Diets
- Vegetarianism and Veganism
- Christmas Traditions
- Animals

- Fruits And Vegetables


  1. Adobe Reader
  2. Adware
  3. Altavista
  4. AOL
  5. Apple Macintosh
  6. Application software
  7. Arrow key
  8. Artificial Intelligence
  9. ASCII
  10. Assembly language
  11. Automatic translation
  12. Avatar
  13. Babylon
  14. Bandwidth
  15. Bit
  16. BitTorrent
  17. Black hat
  18. Blog
  19. Bluetooth
  20. Bulletin board system
  21. Byte
  22. Cache memory
  23. Celeron
  24. Central processing unit
  25. Chat room
  26. Client
  27. Command line interface
  28. Compiler
  29. Computer
  30. Computer bus
  31. Computer card
  32. Computer display
  33. Computer file
  34. Computer games
  35. Computer graphics
  36. Computer hardware
  37. Computer keyboard
  38. Computer networking
  39. Computer printer
  40. Computer program
  41. Computer programmer
  42. Computer science
  43. Computer security
  44. Computer software
  45. Computer storage
  46. Computer system
  47. Computer terminal
  48. Computer virus
  49. Computing
  50. Conference call
  51. Context menu
  52. Creative commons
  53. Creative Commons License
  54. Creative Technology
  55. Cursor
  56. Data
  57. Database
  58. Data storage device
  59. Debuggers
  60. Demo
  61. Desktop computer
  62. Digital divide
  63. Discussion groups
  64. DNS server
  65. Domain name
  66. DOS
  67. Download
  68. Download manager
  69. DVD-ROM
  70. DVD-RW
  71. E-mail
  72. E-mail spam
  73. File Transfer Protocol
  74. Firewall
  75. Firmware
  76. Flash memory
  77. Floppy disk drive
  78. GNU
  79. GNU General Public License
  80. GNU Project
  81. Google
  82. Google AdWords
  83. Google bomb
  84. Graphics
  85. Graphics card
  86. Hacker
  87. Hacker culture
  88. Hard disk
  89. High-level programming language
  90. Home computer
  91. HTML
  92. Hyperlink
  93. IBM
  94. Image processing
  95. Image scanner
  96. Instant messaging
  97. Instruction
  98. Intel
  99. Intel Core 2
  100. Interface
  101. Internet
  102. Internet bot
  103. Internet Explorer
  104. Internet protocols
  105. Internet service provider
  106. Interoperability
  107. IP addresses
  108. IPod
  109. Joystick
  110. JPEG
  111. Keyword
  112. Laptop computer
  113. Linux
  114. Linux kernel
  115. Liquid crystal display
  116. List of file formats
  117. List of Google products
  118. Local area network
  119. Logitech
  120. Machine language
  121. Mac OS X
  122. Macromedia Flash
  123. Mainframe computer
  124. Malware
  125. Media center
  126. Media player
  127. Megabyte
  128. Microsoft
  129. Microsoft Windows
  130. Microsoft Word
  131. Mirror site
  132. Modem
  133. Motherboard
  134. Mouse
  135. Mouse pad
  136. Mozilla Firefox
  137. Mp3
  138. MPEG
  139. MPEG-4
  140. Multimedia
  141. Musical Instrument Digital Interface
  142. Netscape
  143. Network card
  144. News ticker
  145. Office suite
  146. Online auction
  147. Online chat
  148. Open Directory Project
  149. Open source
  150. Open source software
  151. Opera
  152. Operating system
  153. Optical character recognition
  154. Optical disc
  155. output
  156. PageRank
  157. Password
  158. Pay-per-click
  159. PC speaker
  160. Peer-to-peer
  161. Pentium
  162. Peripheral
  163. Personal computer
  164. Personal digital assistant
  165. Phishing
  166. Pirated software
  167. Podcasting
  168. Pointing device
  169. POP3
  170. Programming language
  171. QuickTime
  172. Random access memory
  173. Routers
  174. Safari
  175. Scalability
  176. Scrollbar
  177. Scrolling
  178. Scroll wheel
  179. Search engine
  180. Security cracking
  181. Server
  182. Simple Mail Transfer Protocol
  183. Skype
  184. Social software
  185. Software bug
  186. Software cracker
  187. Software library
  188. Software utility
  189. Solaris Operating Environment
  190. Sound Blaster
  191. Soundcard
  192. Spam
  193. Spamdexing
  194. Spam in blogs
  195. Speech recognition
  196. Spoofing attack
  197. Spreadsheet
  198. Spyware
  199. Streaming media
  200. Supercomputer
  201. Tablet computer
  202. Telecommunications
  203. Text messaging
  204. Trackball
  205. Trojan horse
  206. TV card
  207. Unicode
  208. Uniform Resource Identifier
  209. Unix
  210. URL redirection
  211. USB flash drive
  212. USB port
  213. User interface
  214. Vlog
  215. Voice over IP
  216. Warez
  217. Wearable computer
  218. Web application
  219. Web banner
  220. Web browser
  221. Web crawler
  222. Web directories
  223. Web indexing
  224. Webmail
  225. Web page
  226. Website
  227. Wiki
  228. Wikipedia
  229. WIMP
  230. Windows CE
  231. Windows key
  232. Windows Media Player
  233. Windows Vista
  234. Word processor
  235. World Wide Web
  236. Worm
  237. XML
  238. X Window System
  239. Yahoo
  240. Zombie computer

This article is from:

All text is available under the terms of the GNU Free Documentation License: 

Computer keyboard

From Wikipedia, the free encyclopedia


A computer keyboard is a peripheral partially modeled after the typewriter keyboard. Keyboards are designed for the input of text and characters and also to control the operation of a computer.

A 104-key PC US English QWERTY keyboard layout
A 104-key PC US English QWERTY keyboard layout

Physically, computer keyboards are an arrangement of rectangular or near-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.

Roughly 50% of all keyboard keys produce letters, numbers or signs (characters). Other keys can produce actions when pressed, and other actions are available by the simultaneous pressing of more than one action key.


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. With the advent of modern electronics, this is no longer necessary. 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. 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, such as the Dvorak Simplified Keyboard; however, these layouts have yet to gain mainstream popularity.

The number of keys on a keyboard varies from the original standard of 101 keys 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 such as starting a web browser or e-mail client. There also were "Internet keyboards," sold in America 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

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 now common PS/2 or USB connection. Prior to the iMac line of systems, Apple Computer used ADB, a proprietary system, for its keyboard connector.

Wireless keyboards

Wireless computer 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 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 number of keys is to use chording, 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. 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.


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


Microsoft On-Screen Keyboard is software designed for users with limited mobility.
Microsoft On-Screen Keyboard is software designed for users with limited mobility.

In normal usage, the keyboard is used to type text into 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 and releases 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.


A keyboard is also used to type commands in a computer. One famous example on the PC is the Ctrl+Alt+Del combination. With current versions of Windows, this brings up a menu-window including options for handling currently-running applications and shutting down the computer, amongst other things. Under Linux, MS-DOS and some older versions of Windows, Ctrl+Alt+Del performs either a 'cold' or 'warm' reboot.


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 e to eat in NetHack). Keyboards are less than ideal when many keys are to be pressed at once, as the simple keyboard circuitry means that only a certain number of keys will register at one time. A common side effect of this is called "phantom key blocking." Due to the circuit design on older 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. Better keyboards are designed so that this happens infrequently 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.

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 current to flow (i.e. the circuit goes from open to closed), changing the signal strength.
  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.
  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).

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.

Keys on a computer keyboard

  • 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 key / End key
  • Edit keys
    • Return key / Enter key
    • Backspace
    • Insert key
    • Delete key
    • Tab key
  • SysRq / Print screen
  • Break key / Pause key
  • Escape key
  • Menu key
  • Space bar
  • Numpad
  • Function key
  • Power management keys
    • Power key
    • Sleep key
    • Wake key

Customization of keyboard

Sometimes, it is desired to customize the layout of a keyboard or remap the keys. There are several software for this purpose.

  • SharpKeys: free
  • KeyTweak: free
  • Keyboard Layout Manager:commercial

See also

  • Ergonomics
  • Repetitive strain injury
  • Keyboard styles
    • Alphanumeric keyboard
    • Enhanced keyboard
      • AT keyboard
    • Velotype (chorded keyboard)
    • Virtual keyboard
    • Optimus Keyboard
    • Das Keyboard (blank keyboard)
    • EZ-Reach (keyboard)
  • Keyboard layout
    • Dvorak keyboard
    • Maltron keyboard
  • Keyboard technology
    • Membrane keyboard
    • Chiclet keyboard
    • Buckling spring
  • Apple keyboard
  • 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
  • Microsoft Natural keyboard
  • Space-cadet keyboard
  • Touch typing
  • Typing
  • Hunt and peck typing
  • Home row
  • Key jamming
  • Rollover (key)
  • Table of keyboard shortcuts

External links

  • Article on Howstuffworks
  • Interfacing the AT keyboard
  • Keyboard and mouse interfaces pinouts
  • Ergonomics research on alternative keyboard designs
  • Repair4Keyboard - A survey of do-it-yourself guides about repairing and modding computer keyboards.


  1. ^ Brandt, Andrew. "Privacy Watch: Wireless Keyboards That Blab", PC World, 2003-01-29.
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