escape character

A particular nugget of text or something else that tells a computer, say, to stop doing one thing and to look at the next thing a little differently.

Some important/common instances of escape characters in C++:

• \n - inserts a line break (like the BR tag in HTML)
• \t - inserts a horizontal tab
• \v - inserts a vertical tab
• \b - backspace
• \r - carriage return
• \f - form feed
• \a - bell/audio alert
  
  
• \\ - inserts a backslash
• \' - inserts a single quote
• \" - inserts a double quote
• \? - inserts a question mark

The first three examples exist because of the whitespace element (please see that writeup) and are very common.

The last four examples (\,',",?) are necessary because the characters they represent are control characters. They are part of the invisible character set that makes up the code itself, much like angled brackets in HTML. In order for these symbols to appear upon execution, they must be preceded by a backslash. For instance, if you wanted to display the text How are you? you would have to put into the code How are you\?. Otherwise, the compiler would interpret the question mark as something that it's not - or, more simply, as more than a question mark. (I.E.: The ? is used to denote a conditional operator.)

Escape characters may also be used in tandem with hexadecimal numbers and UCS codes to display other obscure letters/symbols; for instance, characters that aren't part of your language.