The backslash ( \ ) is a typographic and/or keyboard mark that is used in some programming languages and other computing contexts.
In Windows systems, for example, the backslash is used to separate elements of a file path, for example: C:\Documents\User\File. In C, Perl and Unix scripting, the backslash indicates that the following character must be treated in some special way. Within the TeX typesetting markup system, the backslash starts tags.
Computer scientist Bob Bemer introduced the backslash to computing in 1961, when he used it in ASCII (American Standard Code For Information Interchange) to represent some Boolean operators in the ALGOL language. The backslash is represented as a keyboard character that is the mirror image of the forward slash ( / ), often just called a slash, which is more widely used in both computing and non-computing contexts. Such marks are known as glyphs -- graphic symbols that provide the appearance or form for a character.
Other terms for the backslash include backslant, backslat, backwhack, bash, escape, hack, reverse slant, reverse slash, reverse solidus, reversed virgule, slosh and whack.