C++ Primer Plus, Sixth Edition (2012)
C. The ASCII Character Set
Computers store characters by using numeric codes. The ASCII (American Standard Code for Information Interchange) code is the most commonly used code in the United States. It’s also a subset (a very small subset) of Unicode. C++ lets you represent most single characters directly by including the character in single quotation marks, as in 'A' for the A character. You can also represent a single character by using the octal or hex code preceded by a backslash; for example, '\012' and '\0xa' both represent the linefeed (LF) character. Such escape sequences can also be part of a string, as in "Hello,\012my dear".
Table C.1 shows the ASCII character set in various representations. When used as a prefix in the table, the ^ character denotes using the Ctrl key.
Table C.1. ASCII Character Set Representations