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Control key
In computing, a Control key Ctrl is a modifier key which, when pressed in conjunction with another key, performs a special operation (for example, Ctrl+C). Similarly 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 Ctrl (Control or Ctl are sometimes used, but it is uncommon). Abbreviations in the language of the keyboard layout also are in use, e.g., the German keyboard layout uses Strg (Steuerung) as required by the German standard DIN 2137:2012-06. There is a standardized keyboard symbol (to be used when Latin lettering is not preferred). This symbol is encoded in Unicode as U+2388 helm symbol ⎈, but it is very rarely used.
On teletypewriters and computer terminals, holding down the Control key while pressing another key would send an ASCII C0 control character, instead of directly reporting a key press to the system. The control characters were used as non-printing characters that signal the terminal or teletypewriter to perform a special action, such as ringing a bell, ejecting a page or erasing the screen, or controlling where the next character will display.
The first 32 ASCII characters are the control characters, representable by a 5-bit binary number. Because ASCII characters were represented as 7 bits, if a key is pressed while the Control key was held down, teletypewriters and terminals would simply set the first 2 bits of a character to 0, converting the character into a control character. For example, the character a has a binary ASCII code of 110 0001. This code would be converted to 000 0001, corresponding to the ASCII character with id 1 (the SOH Character). The table at C0 and C1 control codes § C0 controls shows the ASCII control characters, with the "Caret notation" column showing a caret (^), followed by the character to press while the Control key is held down to generate the character.
If a teletypewriter or terminal is connected to a computer, the software on the computer can interpret control characters it receives however it is written to do so; a given control character can be interpreted differently from how it would be interpreted by a teletypewriter or terminal that receives it. For example, Control-C, received from a teletypewriter or terminal, is interpreted as "interrupt the current program" in some command-line interfaces, and Control-E is interpreted by the Emacs text editor as "move the editor cursor to the end of the line".
Computer keyboards directly attached to a computer, as is the case for a personal computer or workstation, distinguish each physical key from every other and report all keypresses and releases to the controlling software. This allows the software to interpret Control key combinations as it chooses, including being able to interpret a combination of the Control key, another modifier key, and a letter, number, or symbol key differently from the way it interprets a combination of the Control key and the letter, number, or symbol key without that other modifier key.
The keyboards of many early computer terminals, including the Teletype Model 33 ASR and Lear-Siegler 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 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.
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.
Hub AI
Control key AI simulator
(@Control key_simulator)
Control key
In computing, a Control key Ctrl is a modifier key which, when pressed in conjunction with another key, performs a special operation (for example, Ctrl+C). Similarly 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 Ctrl (Control or Ctl are sometimes used, but it is uncommon). Abbreviations in the language of the keyboard layout also are in use, e.g., the German keyboard layout uses Strg (Steuerung) as required by the German standard DIN 2137:2012-06. There is a standardized keyboard symbol (to be used when Latin lettering is not preferred). This symbol is encoded in Unicode as U+2388 helm symbol ⎈, but it is very rarely used.
On teletypewriters and computer terminals, holding down the Control key while pressing another key would send an ASCII C0 control character, instead of directly reporting a key press to the system. The control characters were used as non-printing characters that signal the terminal or teletypewriter to perform a special action, such as ringing a bell, ejecting a page or erasing the screen, or controlling where the next character will display.
The first 32 ASCII characters are the control characters, representable by a 5-bit binary number. Because ASCII characters were represented as 7 bits, if a key is pressed while the Control key was held down, teletypewriters and terminals would simply set the first 2 bits of a character to 0, converting the character into a control character. For example, the character a has a binary ASCII code of 110 0001. This code would be converted to 000 0001, corresponding to the ASCII character with id 1 (the SOH Character). The table at C0 and C1 control codes § C0 controls shows the ASCII control characters, with the "Caret notation" column showing a caret (^), followed by the character to press while the Control key is held down to generate the character.
If a teletypewriter or terminal is connected to a computer, the software on the computer can interpret control characters it receives however it is written to do so; a given control character can be interpreted differently from how it would be interpreted by a teletypewriter or terminal that receives it. For example, Control-C, received from a teletypewriter or terminal, is interpreted as "interrupt the current program" in some command-line interfaces, and Control-E is interpreted by the Emacs text editor as "move the editor cursor to the end of the line".
Computer keyboards directly attached to a computer, as is the case for a personal computer or workstation, distinguish each physical key from every other and report all keypresses and releases to the controlling software. This allows the software to interpret Control key combinations as it chooses, including being able to interpret a combination of the Control key, another modifier key, and a letter, number, or symbol key differently from the way it interprets a combination of the Control key and the letter, number, or symbol key without that other modifier key.
The keyboards of many early computer terminals, including the Teletype Model 33 ASR and Lear-Siegler 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 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.
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.