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Backslash
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The backslash ( \ ) is a typographical mark (glyph) used chiefly in computing. It was first introduced to computers in 1960 by 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.
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.
lass="link1" onMouseover='showByLink("m805056",this)' onMouseout='hide("m805056")'href="http://www.absoluteastronomy.com/topics/Bob_Bemer">Bob Bemer introduced the \ character into ASCII, on September 18, 1961, as the result of character frequency studies.
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Encyclopedia
The backslash ( \ ) is a typographical mark (glyph) used chiefly in computing. It was first introduced to computers in 1960 by 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.
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.
Usage
Bob Bemer introduced the \ character into ASCII, on September 18, 1961, 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.
In many programming languages such as C and Perl and in Unix scripting languages, 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 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 Haskell, the backslash is used both to introduce special characters and to introduce lambda functions (since it is a reasonable approximation in ASCII of the Greek letter lambda, ?).
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
We split each long line into two lines using backslash-newline; this is like using one long line, but is easier to read.
The Microsoft Windows system API can accept either the backslash or slash to separate directory and file components of a path, but the Microsoft convention is to use a backslash, and APIs that return paths put backslash in. The slash would have been the preferred path delimiter, but MS-DOS 2 added the backslash to allow paths to be typed into the command shell while retaining compatibility with CP/M—before directories were supported—where the slash was chosen as the command-line option indicator. For instance you could still use the "wide" option to the "dir" command by typing "dir/w", yet you can run the program "w" in the subdirectory "dir" with "dir\w". World Wide Web URL paths always exclusively contain slashes, sometimes referred to as "forward" slashes for clarity.
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 in Korean encoding, the code point for backslash is the won currency symbol (? or W). Computer programs (such as Windows filenames) still treat it as a backslash in these environments, causing confusion. Due to extensive use of the backslash code to represent the yen mark in text, some Unicode fonts like MS Mincho render the backslash character as a ¥, so the Unicode characters 00A5 (¥) and 005C (\) look 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.
External links
- Larry Osterman (2005-06-24),
- Bob Bemer,
- by The Linux Information Project (LINFO)
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