Percent sign
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The percent sign (%) is the symbol used to indicate a percentage (that the preceding number is divided by one hundred). It is represented in Unicode by U+0025.
Related signs include the permille sign ‰ (Unicode: U+2030) and the per ten thousand sign ‱ (Unicode: U+2031; also known as a basis point), which indicate that a number is divided by one thousand or ten thousand respectively. Higher proportions use parts-per notation.
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[edit] Spacing
There is no consensus as whether or not to include a space between the number and percent sign. The ISO 31-0 standard requires a space and the TeX typesetting system encourages it [1][2]. This is in accordance with the general rule of adding a non-breaking space between a numerical value and its corresponding unit of measurement. However, style guides – such as the Chicago Manual of Style, commonly prescribes to write the number and percent sign without any space in between [3].
[edit] Evolution
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The factual accuracy of this section is disputed. Please see the relevant discussion on the talk page |
The symbol evolved from a symbol similar except for a horizontal line instead of diagonal (c. 1650), which in turn evolved from an abbreviation of "P cento" (c. 1425, from the Italian per cento "for a hundred")[4].
 "%" in the 15th century, an abbreviation of per cento |
 "%" in the 17th century, with only the o from cento remaining |
 "%" as soon as the 18th century; note the diagonal line |
A different reference[5] tells a similar story. The phrase "per cento" had several different abbreviations (e.g. "per 100", "p 100", "p cento", etc.). At some point a scribe of some sort used the abbreviation "pc" with a tiny loop (used in Italian numeration for primo, secondo, etc.). The "pc" with a loop eventually evolved a horizontal fraction sign and lost the "per". In modern times, we use a solidus instead of the horizontal fraction bar.
[edit] Usage in computers
In Unicode, there is also an "ARABIC PERCENT SIGN" ("٪"U+066A), which has the circles replaced by square dots set on edge.
In computing, the percent character is also used for the modulo operation in programming languages that derive their syntax from the C programming language, which in turn acquired this usage from the earlier B programming language.[6] The ASCII code for the percent character is 37, or 0x25 in hexadecimal. In the textual representation of URIs, a % immediately followed by a 2-digit hexadecimal number denotes an octet specifying (part of) a character that might otherwise not be allowed in URIs (see percent-encoding). Names for the percent sign include percent sign (in ITU-T), mod, grapes (in hacker jargon), and the humorous double-oh-seven (in INTERCAL).
In SQL, the percent sign is a wildcard character in "LIKE" expressions, for example SELECT * FROM table WHERE fullname LIKE 'Lisa %' will fetch all records whose names start with "Lisa "
In TeX and PostScript, a % denotes a line comment.
In Basic, a trailing % after a variable name marks it as an integer.
In the command processors COMMAND.COM (DOS) and CMD.EXE (OS/2 and Windows), %1, %2,... stand for the first, second,... parameters of a batch file. %VAR1% represents the value of an environment variable named VAR1. Thus:
set PATH=c:\;%PATH%
sets a new value for PATH, the old value preceded by "c:\;".
[edit] Usage in linguistics
In linguistics, the percent sign is prepended to an example string to show that it is judged well-formed by some speakers and ill-formed by others. This may be due to differences in dialect or even individual idiolects. This is similar to the asterisk to mark ill-formed strings, the question mark to mark strings where well-formedness is unclear, and the number sign to mark strings that are syntactically well-formed but semantically nonsensical.
[edit] See also
[edit] References
- ^ Quantities and units -- Part 0: General principles. International Organization for Standardization (1999-12-22). Retrieved on 2007-01-05.
- ^ Heldoorn, Marcel (2002-08-01). The SIunits package (PDF). Comprehensive TeX Archive Network. Retrieved on 2007-01-05.
- ^ The Chicago Manual of Style. University of Chicago Press (2003). Retrieved on 2007-01-05.
- ^ Weaver, Douglas. The History of Mathematical Symbols. Retrieved on 2006-07-18.
- ^ U+0025 PERCENT SIGN.
- ^ Thompson, Ken (1996). Users' Reference to B.
