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Control characters are often rendered into a printable form known as caret notation by printing a caret (^) and then the ASCII character that has a value of the control character plus 64. Control characters generated using letter keys are thus displayed with the upper-case form of the letter.
In 1973, ECMA-35 and ISO 2022 [18] attempted to define a method so an 8-bit "extended ASCII" code could be converted to a corresponding 7-bit code, and vice versa. [19] In a 7-bit environment, the Shift Out would change the meaning of the 96 bytes 0x20 through 0x7F [a] [21] (i.e. all but the C0 control codes), to be the characters that an 8-bit environment would print if it used the same code ...
Like other character encodings, ASCII specifies a correspondence between digital bit patterns and character symbols (i.e. graphemes and control characters). This allows digital devices to communicate with each other and to process, store, and communicate character-oriented information such as written language.
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 the control-codes outside of the range 1–26, the notation extends to the adjacent, non-alphabetic ASCII characters. Often a control character can be typed on a keyboard by holding down the Ctrl and typing the character shown after the caret.
In many GUIs and applications, Control+Z (⌘ Command+Z on macOS) can be used to undo the last action. In many applications, earlier actions than the last one can also be undone by pressing Control+Z multiple times. Control+Z was one of a handful of keyboard sequences chosen by the program designers at Xerox PARC to control text editing.
1 Control-C has typically been used as a "break" or "interrupt" key. 2 Control-D has been used to signal "end of file" for text typed in at the terminal on Unix / Linux systems. Windows, DOS, and older minicomputers used Control-Z for this purpose. 3 Control-G is an artifact of the days when teletypes were in use. Important messages could be ...
SO/SI control characters also are used to display VT100 pseudographics. Shift In is also used in the 2G variant [ 4 ] of SoftBank Mobile 's encoding for emoji . The ISO/IEC 2022 standard ( ECMA -35, JIS X 0202) standardises the generalized usage of SO and SI for switching between pre-designated character sets invoked over the 0x20–0x7F byte ...