Computers are everywhere -- even hotel room locks and car keychains use them. For most people, computers revolve around data input. The most common human data input method is the standard 104-key keyboard. While there are several vendors and some variations between types of keyboards, the basics don't change much between them.
General Typing Area
The general typing area is dominated by the 46 alpha-numeric keys. Each alpha-numeric key produces two symbols, the second reached by holding down the "Shift" key while pressing the alpha-numeric key. The standard layout for this part of the keyboard is the QWERTY layout, which dates back to 1878. Alternative layouts include variations on QWERTY for different languages and the Dvorak keyboard layout. The alpha-numeric key area is surrounded by keys for moving the cursor. The "Enter" key advances text on the screen by one line or ends a paragraph in most word processing and email programs. The "Spacebar" inserts a space. The "Tab" key moves the cursor to the right by a fixed number of spaces. Holding down the "Shift" and "Tab" keys at the same time will move the cursor to the left the same distance as the "Tab" key moves it to the right. The "Backspace" key deletes characters to the left of the cursor.
CTRL, ALT and Function Keys
Computer keyboards have specific function keys. Some, such as the "Alt" and "Ctrl" keys, are held down with other keys, for example "Ctrl-C" for copying. On Macintosh keyboards, the "Command" key replaces the "Ctrl" key, and Windows keyboards have the "Windows" key for opening the Start menu with a single keystroke or opening specific programs in conjunction with another key. In addition to these keys, most keyboards also have function keys at the top row of the keyboard or down the right edge. Function keys are labeled "F1" through "F10" or "F12." Most function keys have uses that pertain to the operating system and are uniform across programs, such as "F1" to open the Help system. Many programs repurpose function keys for program-specific uses. Many laptop keyboards have additional, hardware-specific functions tied to the function keys, accessed by holding down the function key and a special "Fn" key. These include controls for adjusting the screen brightness, speaker volume or turning the Number Lock function on or off.
Navigation and Editing Keys
To the right of the alpha-numeric keys are navigation and editing keys; these include the cursor keys, which have four arrows. These arrows move the cursor one space in the indicated direction. Holding down the "Shift" key with the appropriate arrow key will move the cursor one word left or right, or one paragraph up or down in most text editing programs. Above these keys are a block of six keys that include the "Insert" and "Delete" keys, the "Home" and "End" keys, and the "Page Up" and "Page Down" keys. The "Insert" key toggles text insertion; when active, new text is inserted when entered. When inactive, new text overwrites existing text. The "Delete" key deletes characters to the right of the cursor. The "Home" and "End" keys move the cursor to the beginning and end of a file, respectively, while "Page Up" and "Page Down" move the cursor one full screen up or down the file.
Nearly every keyboard also has keys that date back to the dawn of computing. The "Esc" key interrupts a program automatically. The "PrtScrn" key used to send the contents of the screen to a text file or line printer, and is used to take screen captures. The "Scroll Lock" (usually spelled "ScrLk") key prevents the text in the screen buffer from scrolling (or, in some programs, allows you to scroll through a volume of text without changing the cursor position) and the "Pause/Break" key tells a shared time computer system that your computer is about to send data. Many keyboards omit the "ScrLk" and "Pause/Break" keys completely, as few programs use them at all.
At the far right of most full-sized keyboards is a numeric keypad. This keypad is activated when the "NumLock" key is toggled -- this will be indicated with a light somewhere on the keyboard. Any numbers entered here will appear on the screen. When the "NumLock" key is turned off, the numeric keypad replicates the "Arrow," "Home," "End," "PageUp" and "PageDown" keys. Most numeric keypads have their own "Enter" key to speed up data entry, additional keys for four-function arithmetic operations and sometimes other mathematical symbols, such as the equal sign and parentheses. Some special functions (such as entering ASCII codes in Windows) require holding down the "Alt" key and typing the ASCII code number with the numeric keypad, rather than the numbers at the top of the alpha-numeric keyboard area.
Hardware and Multimedia Keys
Keyboard manufacturers, and especially operating system publishers, often add keys with specific functions. These can give direct access to hardware functions such as controlling volume, pausing or playing multimedia files, or opening specific programs or Web pages. Some keys also open commonly used programs such as the Calculator program. Some keyboards have custom buttons that can be assigned to open specific programs with a single keystroke.
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