Control key
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It has been suggested that Control key (Macintosh) be merged into this article or
section. (Discuss)
A Control key (marked "Ctrl") on a modern Windows keyboard
In computing, a Control key is a modifier key which, when pressed in conjunction with another
key, will perform a special operation (for example, Control-Alt-Delete); similar to the Shift key,
the Control key rarely performs any function when pressed by itself. The control key is located
on or near the bottom left side of most keyboards. It is usually labeled Ctrl, but sometimes
Control or Ctl is seen, and it can be graphically represented as an “up arrowhead” (U+2303, ⌃),
or simulated with a caret (^).
Contents
[hide]
1 History
2 Notation
3 Examples
4 Similar concepts
5 See also
[edit] History
Control key on an Apple wireless keyboard
On teletypewriters and early keyboards, holding down the Control key while pressing another
key zeroed the leftmost 2 bits of the 7 bits in the generated ASCII character. This allowed the
operator to produce the first 32 characters in the ASCII table. These are non-printing characters
that signal the computer to control where the next character will be placed on the display device,
eject a printed page or erase the screen, ring the terminal bell, or some other operation. Aptly,
these characters are also called control characters.
Note that using the Control key with either lowercase c or uppercase C will generate the same
ASCII code on a teletypewriter because holding down the control key grounds (zeros the voltage
on) the 2 wires used to carry the leftmost 2 bits from the keyboard. 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 additional flexibility is not often taken advantage of and it usually does not matter, for
example, whether the control key is pressed in conjunction with an upper or a lower case
character.
When the original purpose of the ASCII control characters became either obsolete or seldom
used, later software appropriated the Control key combinations for other purposes.
Because on older keyboards the Control key was located on the left of the keyboard, some
people remap the keys to exchange Control and Caps Lock, finding the traditional location more
ergonomic for using programs benefiting from use of the Control key. This is sometimes called
"Unix" layout; Sun5 model keyboards from Sun Microsystems came in two versions; Sun5pc
and Sun5unix, with the latter having more traditional placing of some keys, including the Control
key. The OLPC XO-1 keyboard also has the Control key in this location. Keyboards for different
computer systems with this placement of the Control key are also sold as extra peripherals, see
for example the Happy Hacking Keyboard.
Others leave the control key in the lower-left corner of the keyboard, and press it using the side
of their palm. The choice of location for the control key often comes down to the typist's hand
shape and posture.
[edit] Notation
There are several common notations for pressing the Control key in conjunction with another
key. Each notation below means press and hold Control while pressing the x key:
^X Caret notation
C-x Emacs notation
CTRL-X Old Microsoft notation
Ctrl+X New Microsoft notation
Ctrl/X OpenVMS notation
Mac OS X uses the Traditional notation.
[edit] Examples
Different application programs, user interfaces, and operating systems use the various control
key combinations for different purposes.
Unix (command
Emacs (if different
Microsoft line and
Key combination from Unix command
Windows/KDE/GNOME programs using
line)
readline)
Ctrl+A Select all Beginning of line
Ctrl+B Bold Backward one character
terminate
Ctrl+C FFL Compound command
application
Forward delete, or
Font Window (Word
if line is empty,
Ctrl+D Processing); Add to Forward delete
end of input
bookmarks (Browsers)
(traditional Unix)
Center Alignment (Word
Ctrl+E End of line
Processing)
Find (usually a small piece of
Ctrl+F Forward one character
text in a larger document)
Quit – aborts current
Ctrl+G Go To (Line number) Bell
operation
hCtrl+H Replace, or History in Delete previous
Help key
browsers character
Italic (sometimes incremental Command line
Ctrl+I Same as Tab key
search) completion
LFD (to evaluate Lisp
Ctrl+J Line feed (LFD)
expressions)
Cut ("Kill") text between cursor and end
Ctrl+K Insert Hyperlink (Word 2007)
of line
Redraw
window/terminal, and
Ctrl+L Create List Clear screen
recenter view around
current line
Decrease margin by 1/2 inch
Ctrl+M Same as Enter key
(Microsoft Word)
New (window, document, Next line (in
Ctrl+N Next line
etc.) history)
Insert ("open") new
Ctrl+O Open Flush output
line
Previous line (in
Ctrl+P Print Previous line
history)
Resume
Ctrl+Q Quit application Literal insert
transmission
Search backwards
Ctrl+R Refresh page Search backwards
in history
Ctrl+S Save Pause Search forward
transmission
Ctrl+T Open New Tab Transpose characters
Delete text
Prefix numerical
between
Ctrl+U Underline argument to next
beginning of line
command
and cursor
Ctrl+V Paste Literal insert Page down
Delete previous
Ctrl+W Close window or tab Cut
word
Ctrl+X Cut Compound command
Redo (sometimes
Ctrl+Y Ctrl+Shift+Z is used for Paste
this)
Ctrl+Z Undo Suspend program Iconify window
Same as Modifier key
Ctrl+[ Same as Esc key
(Alt key)
Ctrl+End
Bottom (end of document or undefined or Bottom (end of text
window) rarely used buffer)
Ctrl+Home
Top (start of document or undefined or Top (start of text
window) rarely used buffer)
Ctrl+Ins Copy undefined or Copy
rarely used
undefined or Scroll window to the
Ctrl+PgDn Next tab
rarely used right
undefined or Scroll window to the
Ctrl+PgUp Previous tab
rarely used left
Ctrl+Tab Next window or tab undefined or rarely used
Ctrl+Shift+Tab Previous window or tab undefined or rarely used
undefined or
Ctrl+← Previous word Previous word
rarely used
undefined or
Ctrl+→ Next word Next word
rarely used
undefined or
Ctrl+Delete Delete Next word Delete Next word
rarely used
undefined or
Ctrl+Backspace Delete Previous word Delete Previous word
rarely used
undefined or rarely
Ctrl+Alt+Backspace undefined or rarely used Restart X11
used
Ctrl+Shift+Esc Task Manager unknown unknown
Reboot (when on undefined or rarely
Ctrl+Alt+Delete Task Manager
the console) used
[edit] Similar concepts
Generally, the Command key, labeled with the ⌘ symbol on Apple Macintosh computers,
performs the equivalent functions in Mac OS X and Mac OS applications (for example, ⌘-C
copies, while ⌘-P prints; the same holds for saving, cutting, and pasting).[clarification needed]
Macintoshes also have a Control key, but it has different functionality. Most Mac's and Apple's
mouses do not have a 2nd mouse button, since Mac OS doesn't require one. If one does want to
right-click (or "secondary click", as Apple calls it), that's where the control-key comes in.
Holding it down while clicking triggers a "right click".[clarification needed]
It is mostly used as a modifier key for key-combinations.
When pressing Control and clicking the mouse-button, you will get a contextual menu.
This is a compatibility feature for users with one-button mice; users with two-button mice
just use the right mouse-button, with no modifiers.
It is used in the command line interface with programs made for that interface.
Under Mac OS X, the Control key allows the use of Emacs-style key combinations in
most text entry fields. For example, Ctrl-A moves the caret to the start of the paragraph,
Ctrl-L vertically centers the current line in the editing field, Ctrl-K cuts text to the end of
the line to a kill ring separate from the normal clipboard, etc.
[edit] See also
Alt key
Break key
Control characters
Control-Alt-Delete
Function key
Keyboard layout
Modifier key
IBM/Windows keyboard (US layout)
v • d • e
PrtSc/ Pause
ScrL
Esc F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 SysR /
k
q Break
NumL
Ins Home PgUp
k / * -
Del End PgDn 7 8 9 +
4 5 6
↑ 1 2 3
Ent
← ↓ → 0 .
[hide]
v • d • e
Keyboard keys
Dead keys Compose
Control · Shift · Alt/Option (Apple) · AltGr · Command/Meta
Modifier
(Apple/MIT/Sun keyboards) · Windows · X · Super · Hyper · Fn (compact
keys
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
System request/Print screen · Break/Pause · Escape · Menu · Numeric
Misc. keypad · Function · Power management (Power, Sleep, Wake) · Language
input · Any key · Macro key
Retrieved from "http://en.wikipedia.org/wiki/Control_key"
Categories: Computer keys
Hidden categories: Articles to be merged from September 2009 | All articles to be merged | All
pages needing cleanup | Wikipedia articles needing clarification from December 2009
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This page was last modified on 25 February 2010 at 12:20.
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