From ECDL.web

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.

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.

Some keyboards have a built-in smart card reader.

Contents 1 Designs 1.1 Connection types 2 Usage 3 Keys on a computer keyboard

[edit] Designs

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 are not in widespread use.

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.

[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 connector and now USB.

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.

[edit] Usage

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.

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.

[edit] 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
• Numeric keypad
• Function key
• Power management keys
  • Power key
  • Sleep key
  • Wake key