What are ASCII control characters?

Control characters are the non-printing codes 0-31 plus DEL (127) in ASCII. Instead of displaying a glyph, they signal actions such as newline, tab, backspace or interrupt. They form the C0 control set.

What is caret notation?

Caret notation writes a control character as ^ followed by a letter, mapping Ctrl+key to a code. For example ^C is ETX (3), produced by pressing Ctrl+C, and ^? is DEL (127). The letter equals the code plus 64.

What is the difference between LF and CR?

Line Feed (LF, 10, \n) moves down one line, while Carriage Return (CR, 13, \r) returns the cursor to the start of the line. Unix uses LF alone for newlines, Windows uses CR+LF, and classic Mac used CR alone.

Why does Ctrl+C interrupt a program?

Ctrl+C sends the ETX control character (3), which terminals translate into a SIGINT signal. SIGINT asks the foreground program to stop, which is why it cancels running commands.

Are control characters still used today?

Yes. NUL, LF, CR, HT (tab) and ESC are used constantly in text, terminals and protocols. ESC in particular begins every ANSI escape sequence. Others like the file/group/record/unit separators survive in data formats and legacy systems.

Control Characters Reference

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The non-printing side of ASCII

The first 32 ASCII codes, plus DEL at 127, are control characters: they do not display a glyph but instead instruct the device to perform an action such as advancing a line, sounding a bell, or interrupting a program. This reference lists every C0 control character with its decimal and hex value, caret notation, C escape sequence where one exists, abbreviation, full name and a note on its use.

How it works

Each control character has a fixed code. Caret notation is derived directly from that code: for codes 0-31 the caret letter is String.fromCharCode(code + 64), so code 3 becomes ^C and code 27 becomes ^[; DEL (127) is the special case ^?. Where the C language defines a backslash escape — \n, \r, \t, \0, \a, \b, \f, \v, \e — it is shown so you can recognise the character in source code. Search matches any of these forms at once.

Tips and notes

LF (10) is \n and CR (13) is \r; the CR+LF pair is the classic Windows line ending, while Unix uses LF alone.
Ctrl+C sends ETX (3) which the terminal turns into a SIGINT to interrupt the running program; Ctrl+D sends EOT (4), signalling end-of-file.
ESC (27) is the gateway to ANSI escape sequences used for cursor movement and color in the terminal.
The separators FS, GS, RS, US (28-31) form a nested delimiter hierarchy still occasionally used in data interchange formats.