
In
computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, ...
, a Control key is a
modifier key
In computing, a modifier key is a special key (or combination) on a computer keyboard that temporarily modifies the normal action of another key when pressed together. By themselves, modifier keys usually do nothing; that is, pressing any of the , ...
which, when pressed in conjunction with another key, performs a special operation (for example,
); 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 (in accordance with the international standard
ISO/IEC 9995-2), with many featuring an additional one at the bottom right.
On keyboards that use English abbreviations for key labeling, it is usually labeled (rarely, or is seen). Abbreviations in the language of the keyboard layout also are in use, e.g., the
German keyboard layout uses as required by the German standard
DIN
DIN or Din or din may refer to:
People and language
* Din (name), people with the name
* Dīn, an Arabic word with three general senses: judgment, custom, and religion from which the name originates
* Dinka language (ISO 639 code: din), spoken by ...
2137:2012-06. Also, there is a standardized keyboard symbol (to be used when Latin lettering is not preferred), given in
ISO/IEC 9995-7 as symbol 26, and in ISO 7000 "Graphical symbols for use on equipment" as symbol ISO-7000-2028. This symbol is encoded in
Unicode
Unicode, formally The Unicode Standard,The formal version reference is is an information technology standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard, ...
as U+2388 (⎈).
History
On
teletypewriters and early
keyboards, holding down the Control key while pressing another key zeroed the leftmost two
bit
The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented a ...
s of the seven bits in the generated
ASCII
ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because ...
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. For example, the character or "G", whose ASCII code is 71 in
base 10, or
100 0111
in
binary, would be transformed into the binary code
000 0111
(7 in decimal), which is assigned to the
bell character. Aptly, these characters are also called ''
control characters''.
Using the key with either lowercase letters (e.g. , ASCII code
100 0011
) or uppercase letters (, ASCII
110 0011
) will generate the same ASCII code on a teletypewriter, because holding down the control key
grounds (zeros the voltage on) the two wires used to carry the leftmost two bits from the keyboard, ignoring their modification by the key. In modern computers, the interpretation of keypresses is generally left to the
software
Software is a set of computer programs and associated software documentation, documentation and data (computing), data. This is in contrast to Computer hardware, hardware, from which the system is built and which actually performs the work.
...
. Modern keyboards distinguish each physical key from every other and report all keypresses and releases to the controlling software.
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.
Location
The keyboards of many early
computer terminals, including the
Teletype Model 33 ASR and
Lear-Siegler
Lear Siegler Incorporated (LSI) is a diverse American corporation established in 1962. Its products range from car seats and brakes to weapons control systems for military fighter planes. The company's more than $2 billion-a-year annual sales come ...
ADM-3A, and early models of the
IBM PC, positioned the Control key on the left of the keyboard, whereas
caps lock resides in the same position on most modern keyboards. The traditional layout was preserved for later
workstation systems and is often associated with
Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...
workstations. Keyboards from
Sun Microsystems came in two layouts; "Unix" and "PC-style", with the Unix layout having the traditional placing of the Control key and other keys. The keyboards produced for
One Laptop Per Child computers also have the Control key in this location. Other vendors produce keyboards for different computer systems with this placement of the Control key, such as the
Happy Hacking Keyboard
The Happy Hacking Keyboard is a small computer keyboard produced by PFU Limited of Japan, codeveloped with Japanese computer scientist and pioneer Eiiti Wada. Its reduction of keys from the common 104-key layout down to 60 keys in the profession ...
.
Some users of keyboards with caps lock on the left 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. Keyboard layout preferences specifically to address this need are available in some operating systems.
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.
Notation
There are several common notations for pressing the Control key in conjunction with another key. Each notation below means press and hold while pressing the key:
Table of examples
Different application programs, user interfaces, and operating systems use the various control key combinations for different purposes.
In early
first-person shooters, the left Ctrl key is often used to fire a weapon. In newer games, the key is often used for crouching instead.
Similar concepts
Generally, the
Command key, labeled with the ⌘ symbol on
Apple Macintosh computers, performs the equivalent functions in
classic Mac OS and
macOS
macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac (computer), Mac computers. Within the market of ...
applications (for example, copies, while prints; the same holds for saving, cutting, and pasting).
Macintoshes also have a Control key, but it has different functionality. The original Apple mouse design reduced complexity by only offering one button. As the interface developed,
contextual menus were offered to access extra options. Another button was needed to access these. On Unix and Windows, the user had other mouse buttons to use. On Classic Mac OS and macOS, the Control key is used to invoke a "right-click". Apple calls this a "secondary click" as left-handers can choose which side this button is on.
* It is mostly used as a
modifier key
In computing, a modifier key is a special key (or combination) on a computer keyboard that temporarily modifies the normal action of another key when pressed together. By themselves, modifier keys usually do nothing; that is, pressing any of the , ...
for key-combinations.
* Pressing Control and clicking the mouse button will invoke 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.
* In
Quickbooks, the Control Key is used to validate login credentials during OLSU 1016 and OLSU 1013 errors. Keeping it depressed while sending information to the Quickbooks servers fixes the errors.
* Under
macOS
macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac (computer), Mac computers. Within the market of ...
, the Control key allows the use of
Emacs
Emacs , originally named EMACS (an acronym for "Editor MACroS"), is a family of text editors that are characterized by their extensibility. The manual for the most widely used variant, GNU Emacs, describes it as "the extensible, customizable, ...
-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.
References
See also
* Alt key
* Break key
* Control characters
* Control-Alt-Delete
* Function key
* Keyboard layout
A keyboard layout is any specific physical, visual or functional arrangement of the keys, legends, or key-meaning associations (respectively) of a computer keyboard, mobile phone, or other computer-controlled typographic keyboard.
is the actu ...
* Modifier key
In computing, a modifier key is a special key (or combination) on a computer keyboard that temporarily modifies the normal action of another key when pressed together. By themselves, modifier keys usually do nothing; that is, pressing any of the , ...
* IBM Common User Access
{{DEFAULTSORT:Control Key
Computer keys