In the C programming language, an escape sequence is specially delimited text in a character or string literal that represents one or more other characters to the compiler. It allows a programmer to specify characters that are otherwise difficult or impossible to specify in a literal.

An escape sequence starts with a backslash (\) called the escape character and subsequent characters define the meaning of the escape sequence. For example, \n denotes a newline character.

The same or similar escape sequences are used in other, related languages such C++, C#, Java and PHP.

To demonstrate the value of the escape sequence feature, to output the text Foo on one line and Bar on the next line, the code must output a newline between the two words.

The following code achieves the goal via text formatting and a hard-coded ASCII character value for newline (0x0A). This behaves as desired with the words on sequential lines, but an escape sequence has advantages.

The \n escape sequence allows for shorter code by specifying the newline in the string literal, and for faster runtime by eliminating the text formatting operation. Also, the compiler can map the escape sequence to a character encoding system other than ASCII and thus make the code more portable.

An escape sequence changes how the compiler interprets character data in a literal. For example, \n does not represent a backslash followed by the letter n. The backslash escapes the compiler's normal, literal way of interpreting character data. After a backslash, the compiler expects subsequent characters to complete one of the defined escape sequences, and then translates the escape sequence into the characters it represents.

This syntax does require special handling to encode a backslash character – since it is a metacharacter that changes literal interpretation behavior; not the literal backslash character. The issue is solved by using two backslashes (\\) to mean one.