The notation is often used to describe keyboard shortcuts even though the control character is not actually used (as in "type ^X to cut the text").
Seven ASCII control characters map outside the upper-case alphabet: 0 (NUL) is ^@, 27 (ESC) is ^[, 28 is ^\, 29 is ^], 30 is ^^, 31 is ^_, and 127 (DEL) is ^?.
Examples are "^M^J" for the Windows CR, LF newline pair, and describing the ANSI escape sequence to clear the screen as "^[[3J".
[2] Many computer systems allow the user to enter a control character by holding down Ctrl and pressing the letter used in the caret notation.
Caret notation is used to describe control characters in output by many programs, particularly Unix terminal drivers and text file viewers such as more and less commands.
The GSTrans string processing API on the operating systems for the Acorn Atom and the BBC Micro, and on RISC OS for the Acorn Archimedes and later machines, use the vertical bar character | in place of the caret.
For example, |M (pronounced "control em", the same as for the ^M notation) is the carriage return character, ASCII 13.