The backslash ( ) is a typographical mark (
glyph) used chiefly in computing. It was first introduced to computers in 1960by Bob Bemer. [ [http://www.thocp.net/biographies/bemer_bob.htm Mini-Biography of Bob Bemer] ] Sometimes called a reverse solidus or an oblique, it is the mirror image of the common slash. It is also known as a slosh. [" Macquarie Dictionary" (3rd edition)] In colloquial speech, it is sometimes called a whack (however that term is considered to be properly a synonymonly for the forward slash). [ [http://www.computerhope.com/jargon/w/whack.htm Whack] ]
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. [ [http://www.catb.org/jargon/html/A/ASCII.html ASCII] ]
Bob Bemer introduced the character into ASCII on 1961 September 18 as the result of character frequency studies. In particular the was introduced so that the ALGOL boolean operators "∧" (AND) and "∨" (OR) could be composed in ASCII as "/" and "/" respectively. [http://home.ccil.org/~remlaps/www.bobbemer.com/BRACES.HTM]
Unixsystems, 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. In various regular expressionlanguages it acts as a switch, changing literal characters into metacharacters and vice versa. The backslash is used similarly in the TeX typesettingsystem and in RTF files to begin markup tags.
In the context of line-oriented text, especially
source codefor some programming languages, it is often used at the end of a line to indicate that the trailing newlinecharacter 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 [ [http://www.gnu.org/software/make/manual/make.html GNU `make' ] ]
We split each long line into two lines using backslash-newline; this is like using one long line, but is easier to read.In
DOSand 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. [ [http://blogs.msdn.com/larryosterman/archive/2005/06/24/432386.aspx Why is the DOS path character ""?] ]
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 646encoding (a 7-bit code based on ASCII), the code pointthat would be used for backslash in ASCII is instead a yenmark (¥), while on Korean computer keyboards, the backslash corresponds to the wonsymbol (₩ or W). Many Japanese environments nonetheless treat it like a backslash, causing confusion. [ [http://blogs.msdn.com/michkap/archive/2005/09/17/469941.aspx When is a backslash not a backslash?] ] To add to the confusion, some fonts, like MS Mincho, render the backslash character as a ¥, so the Unicodecharacters 00A5 (¥) and 005C () look identical when these fonts are selected.
mathematics, a backslash-like symbol is used for the set difference.
MATLAB, the backslash is used for left matrix divide, while the slash is for right matrix divide.
* Larry Osterman (2005-06-24), [http://blogs.msdn.com/larryosterman/archive/2005/06/24/432386.aspx Why is the DOS path character ""?]
* Bob Bemer, [http://www.trailing-edge.com/~bobbemer/BACSLASH.HTM How ASCII got its backslash]
* [http://www.bellevuelinux.org/backslash.html Backslash Definition] by The Linux Information Project (LINFO)
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