![ISOIEC-9995-7-026--ISO-7000-2028--Symbol-for-Control](https://upload.wikimedia.org/wikipedia/commons/b/bf/ISOIEC-9995-7-026--ISO-7000-2028--Symbol-for-Control.svg)
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, e ...
, 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 Shift key is a modifier key on a keyboard, used to type capital letters and other alternate "upper" characters. There are typically two shift keys, on the left and right sides of the row below the home row. The Shift key's name originated f ...
, 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
The German keyboard layout is a QWERTZ keyboard layout commonly used in Austria and Germany. It is based on one defined in a former edition (October 1988) of the German standard DIN 2137-2. The current edition DIN 2137-1:2012-06 standardizes it a ...
uses as required by the German standard
DIN 2137:2012-06. Also, there is a standardized keyboard symbol (to be used when Latin lettering is not preferred), given in
ISO/IEC 9995
ISO/IEC 9995 ''Information technology — Keyboard layouts for text and office systems'' is an ISO/IEC standard series defining layout principles for computer keyboards. It does not define specific layouts but provides the base for national and ind ...
-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 Technical standard, standard for the consistent character encoding, encoding, representation, and handling of Character (computing), text expre ...
as U+2388 (⎈).
History
On
teletypewriters and early
keyboards
Keyboard may refer to:
Text input
* Keyboard, part of a typewriter
* Computer keyboard
** Keyboard layout, the software control of computer keyboards and their mapping
** Keyboard technology, computer keyboard hardware and firmware
Music
* Musi ...
, 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 represente ...
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 of ...
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
A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signal the ...
, 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
The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hindu–Arabic numeral ...
, or
100 0111
in
binary
Binary may refer to:
Science and technology Mathematics
* Binary number, a representation of numbers using only two digits (0 and 1)
* Binary function, a function that takes two arguments
* Binary operation, a mathematical operation that t ...
, would be transformed into the binary code
000 0111
(7 in decimal), which is assigned to the
bell character
A bell code (sometimes bell character) is a device control code originally sent to ring a small electromechanical bell on tickers and other teleprinters and teletypewriters to alert operators at the other end of the line, often of an incoming me ...
. Aptly, these characters are also called ''
control character
In computing and telecommunication, a control Character (computing), character or non-printing character (NPC) is a code point (a number) in a character encoding, character set, that does not represent a written symbol. They are used as in-band ...
s''.
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 documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work.
At the lowest programming level, executable code consists ...
. 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 terminal
A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal and ...
s, including the
Teletype Model 33
The Teletype Model 33 is an electromechanical teleprinter designed for light-duty office use. It is less rugged and cost less than earlier Teletype machines. The Teletype Corporation introduced the Model 33 as a commercial product in 1963 after ...
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
The ADM-3A was an influential early video display terminal, introduced in 1976. It was manufactured by Lear Siegler and had a 12-inch screen displaying 12 or 24 lines of 80 characters. It set a new industry low single unit price of $995. Its "du ...
, and early models of the
IBM PC
The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...
, 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
A workstation is a special computer designed for technical or scientific applications. Intended primarily to be used by a single user, they are commonly connected to a local area network and run multi-user operating systems. The term ''workstat ...
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, and ot ...
workstations. Keyboards from
Sun Microsystems
Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, the ...
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 professio ...
.
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 shooter
First-person shooter (FPS) is a sub-genre of shooter video games centered on gun and other weapon-based combat in a first-person perspective, with the player experiencing the action through the eyes of the protagonist and controlling the pl ...
s, 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
The Command key (sometimes abbreviated as Cmd key), , formerly also known as the Apple key or open Apple key, is a modifier key present on Apple keyboards. The Command key's purpose is to allow the user to enter keyboard commands in applicati ...
, labeled with the ⌘ symbol on
Apple Macintosh
The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and software en ...
computers, performs the equivalent functions in
classic Mac OS
Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Macintosh family of personal computers by Apple Computer from 1984 to 2001, starting with System 1 and ending with Mac OS 9. The ...
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 computers. Within the market of desktop and lapt ...
applications (for example, copies, while prints; the same holds for saving, cutting, and pasting).
Macintosh
The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc., Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and ...
es 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 menu
A context menu (also called contextual, shortcut, and pop up or pop-up menu) is a menu in a graphical user interface (GUI) that appears upon user interaction, such as a right-click mouse operation. A context menu offers a limited set of choic ...
s 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
A context menu (also called contextual, shortcut, and pop up or pop-up menu) is a menu in a graphical user interface (GUI) that appears upon user interaction, such as a right-click mouse operation. A context menu offers a limited set of choic ...
. 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
A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...
with programs made for that interface.
* In
Quickbooks
QuickBooks is an accounting software package developed and marketed by Intuit. First introduced in 1983, QuickBooks products are geared mainly toward Small and medium-sized enterprises, small and medium-sized businesses and offer On-premises sof ...
, 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 computers. Within the market of desktop and lapt ...
, 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, s ...
-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
In human–computer interaction and user interface design, cut, copy, and paste are related Command (computing), commands that offer an interprocess communication technique for transferring data (computing), data through a computer's user inter ...
separate from the normal
clipboard
A clipboard is a thin, rigid board with a clip at the top for holding paper in place. A clipboard is typically used to support paper with one hand while writing on it with the other, especially when other writing surfaces are not available. Th ...
, etc.
References
See also
*
Alt key
The Alt key (pronounced or ) on a computer keyboard is used to change (alternate) the function of other pressed keys. Thus, the Alt key is a modifier key, used in a similar fashion to the Shift key. For example, simply pressing ''A'' will ty ...
*
Break key
The Break key (or the symbol ⎉) of a computer keyboard refers to breaking a telegraph circuit and originated with 19th century practice. In modern usage, the key has no well-defined purpose, but while this is the case, it can be used by softwar ...
*
Control characters
In computing and telecommunication, a control character or non-printing character (NPC) is a code point (a number) in a character set, that does not represent a written symbol. They are used as in-band signaling to cause effects other than the ...
*
Control-Alt-Delete
Control-Alt-Delete (often abbreviated to Ctrl+Alt+Del, also known as the "three-finger salute" or "Security Keys") is a computer keyboard command on IBM PC compatible computers, invoked by pressing the Delete key while holding the Control key, C ...
*
Function key
A function key is a key on a computer or terminal keyboard that can be programmed so as to cause an operating system command interpreter or application program to perform certain actions, a form of soft key. On some keyboards/computers, function ...
*
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 actua ...
*
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
Common User Access (CUA) is a standard for user interfaces to operating systems and computer programs. It was developed by IBM and first published in 1987 as part of their Systems Application Architecture. Used originally in the MVS/ESA, VM/CMS, ...
{{DEFAULTSORT:Control Key
Computer keys