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The backslash ( \ ) is a typographical mark (glyph) used chiefly in computing. It was first introduced in 1960 by Bob Bemer.^[1] Sometimes called a reverse solidus, it is the mirror image of the common slash. It is also known as a slosh.^[2] In colloquial speech, it is sometimes called a whack (however that term is considered to be properly a synonym only for the forward slash).^[3]

Other common terms for the character include hack, escape (from C/UNIX), reverse slash, backslant, and backwhack. Also, it is sometimes referred as bash, reverse slant, reversed virgule, or backslat.^[4]

Usage

On Unixcheese systems, and in many programming languages such as C and Perl, the backslash is used to indicate that the character following it should be treated specially. It is sometimes referred to as a knock-down or escape character, though this risks confusion with the character generated by the Esc key. In various regular expression languages it acts as a switch, changing literal characters into metacharacters and vice versa. The backslash is used similarly in the TeX typesetting system and in RTF files to begin markup tags.

In the context of line-oriented text, especially source code for some programming languages, it is often used at the end of a line to indicate that the trailing newline character should be ignored, so that the following line is treated as if it were part of the current line. In this context it may be called a "continuation". The GNU make manual says^[5]

We split each long line into two lines using backslash-newline; this is like using one long line, but is easier to read.

In DOS and Microsoft Windows, either the backslash or slash can be used as the delimiter between directories and filenames in path expressions. This is in contrast to Unix paths and Internet URLs (web addresses), which only use the forward slash. In an early version of DOS, which did not support directories and thus had no need for a path delimiter, the forward slash was used to introduce command-line options (in Unix, the hyphen ["-"] is used for this purpose.) When directories were introduced to DOS, another character had to be chosen to be able to represent the delimiter, and the backslash was selected.^[6]

The backslash's prominence in Microsoft path names might explain why the forward slashes in URLs are occasionally (and erroneously) read out loud as "backslash". It has even led to its erroneous placement in contexts not relating to directories, or computers at all, for that matter. URLs always exclusively contain slashes, sometimes referred to as "forward" slashes in an attempt to clarify the distinction.

In the Japanese ISO 646 encoding (a 7-bit code based on ASCII), the code point that would be used for backslash in ASCII is instead a yen mark (¥), while on Korean computer keyboards, the backslash corresponds to the won symbol (₩ or W). Many Japanese environments nonetheless treat it like a backslash, causing confusion.^[7] To add to the confusion, some fonts, like MS Mincho, render the backslash character as a ¥, so the Unicode characters 00A5 (¥) and 005C (\) look almost identical when these fonts are selected.

In mathematics, a backslash-like symbol is used for the set difference.

In some dialects of the BASIC programming language, the backslash is used as an operator symbol to indicate integer division.

In MATLAB, the backslash is used for left matrix divide, while the slash is for right matrix divide.

Originally, the backslash was intended to be able to form half of the symbols /\ and \/.

References

External links

Larry Osterman (2005-06-24), Why is the DOS path character "\"?
Bob Bemer, How ASCII got its backslash
Backslash Definition by The Linux Information Project (LINFO)

[1] Mini-Biography of Bob Bemer

[2] Macquarie Dictionary (3rd edition)

[3] Whack

[4] ASCII

[5] GNU `make'

[6] Why is the DOS path character "\"?

[7] When is a backslash not a backslash?

[1]

@@ Line 5: / Line 5: @@
 {{punctuation marks|\}}
 ==Usage==
 On [[Unix]]systems, and in many [[programming language]]s such as [[C (programming language)|C]] and [[Perl]], the backslash is used to indicate that the character following it should be treated specially. It is sometimes referred to as a knock-down or [[escape character]], though this risks confusion with the character generated by the ''[[Esc key]]''. In various [[regular expression]] languages it acts as a switch, changing literal characters into [[metacharacter]]s and vice versa.  The backslash is used similarly in the [[TeX]] [[typesetting]] system and in [[Rich Text Format|RTF]] files to begin markup tags.
 In the context of line-oriented text, especially [[source code]] for some [[programming language]]s, it is often used at the end of a line to indicate that the trailing [[newline]] character should be ignored, so that the following line is treated as if it were part of the current line. In this context it may be called a "continuation". The GNU [[make (software)|make]] manual says<ref>[http://www.gnu.org/software/make/manual/make.html GNU `make'<!-- Bot generated title -->]</ref>
@@ Line 11: / Line 11: @@
 We split each long line into two lines using backslash-newline; this is like using one long line, but is easier to read.
 </blockquote>
-In [[DOS]] and [[I Mac]], either the backslash or slash can be used as the delimiter between directories and filenames in [[Path (computing)|path]] expressions. This is in contrast to Unix paths and Internet [[Uniform Resource Locator|URL]]s (web addresses), which only use the [[slash (punctuation)|forward slash]]. In an early version of DOS, which did not support directories and thus had no need for a path delimiter, the forward slash was used to introduce command-line options (in Unix, the hyphen ["-"] is used for this purpose.) When directories were introduced to DOS, another character had to be chosen to be able to represent the delimiter, and the backslash was selected.<ref>[http://blogs.msdn.com/larryosterman/archive/2005/06/24/432386.aspx Why is the DOS path character "\"?]</ref>
+In [[DOS]] and [[ ]], either the backslash or slash can be used as the delimiter between directories and filenames in [[Path (computing)|path]] expressions. This is in contrast to Unix paths and Internet [[Uniform Resource Locator|URL]]s (web addresses), which only use the [[slash (punctuation)|forward slash]]. In an early version of DOS, which did not support directories and thus had no need for a path delimiter, the forward slash was used to introduce command-line options (in Unix, the hyphen ["-"] is used for this purpose.) When directories were introduced to DOS, another character had to be chosen to be able to represent the delimiter, and the backslash was selected.<ref>[http://blogs.msdn.com/larryosterman/archive/2005/06/24/432386.aspx Why is the DOS path character "\"?]</ref>
 The backslash's prominence in Microsoft path names might explain why the forward slashes in [[Uniform Resource Locator|URL]]s are occasionally (and erroneously) read out loud as "backslash". It has even led to its erroneous placement in contexts not relating to directories, or computers at all, for that matter. URLs always exclusively contain [[Slash (punctuation)|slashes]], sometimes referred to as "forward" slashes in an attempt to clarify the distinction.
@@ Line 23: / Line 23: @@
 In [[MATLAB]], the backslash is used for left [[Matrix (mathematics)|matrix]] divide, while the slash is for right matrix divide.
-Originally, the backslash was intended to be able to form half of the symbols [[∧|/\]] and [[∨|\/]] but now it records as nothing. Backslash is also a useful for the copyright.
+Originally, the backslash was intended to be able to form half of the symbols [[∧|/\]] and [[∨|\/]].
 == See also ==