ASCII Character \Backslash
The backslash \ is a typographical mark used mainly in computing and mathematics. It is the mirror image of the common slash /. It is a relatively recent mark, first documented in the 1930s. In many programming languages such as C, Perl, PHP, Python, Unix scripting languages, and many file formats such as JSON, the backslash is used as an escape character, to indicate that the character following it should be treated specially (if it would otherwise be treated literally), or literally (if it would otherwise be treated specially).