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The control characters in ASCII still in common use include: 0x00 (null, NUL, \0, ^@), originally intended to be an ignored character, but now used by many programming languages including C to mark the end of a string. 0x07 (bell, BEL, \a, ^G), which may cause the device to emit a warning such as a bell or beep sound or the screen flashing.
The C0 and C1 control code or control character sets define control codes for use in text by computer systems that use ASCII and derivatives of ASCII. The codes represent additional information about the text, such as the position of a cursor, an instruction to start a new line, or a message that the text has been received.
RFC 2822 refers to control characters that do not include carriage return, line feed or white space as non-whitespace control characters. [35] Except for the control characters that prescribe elementary line-oriented formatting, ASCII does not define any mechanism for describing the structure or appearance of text within a document.
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.
Caret notation is a notation for control characters in ASCII. The notation assigns ^A to control-code 1, sequentially through the alphabet to ^Z assigned to control-code 26 (0x1A). For the control-codes outside of the range 1–26, the notation extends to the adjacent, non-alphabetic ASCII characters.
Category "Cc" control codes can serve a variety of purposes, not limited to format effectors: for example, the default ASCII C0 set includes six format effectors (BS, HT, LF, VT, FF and CR), ten transmission controls, four device controls, four information separators and eight other control codes. [4] Most of these characters play no explicit ...
One example is the VT52 terminal, which allowed the cursor to be placed at an x,y location on the screen by sending the ESC character, a Y character, and then two characters representing numerical values equal to the x,y location plus 32 (thus starting at the ASCII space character and avoiding the control characters).
Some modern text file formats (e.g. CSV-1203 [10]) still recommend a trailing EOF character to be appended as the last character in the file. However, typing Control+Z does not embed an EOF character into a file in either DOS or Windows, nor do the APIs of those systems use the character to denote the actual end of a file.