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Punctuation

apostrophe ( ' )
brackets ( ( ) ), ( [ ] ), ( { } ), ( ⟨ ⟩)
colon ( : )
comma ( , )
dashes ( , , , )
ellipses ( , ... )
exclamation mark ( ! )
full stop/period ( . )
guillemets ( « » )
hyphen ( -, )
question mark ( ? )
quotation marks ( ‘ ’, “ ” )
semicolon ( ; )
slash/stroke ( / )
solidus ( )
Word dividers
spaces ( ) () () ( ) () () ()
interpunct ( · )
General typography
ampersand ( & )
at sign ( @ )
asterisk ( * )
backslash ( \ )
bullet ( )
caret ( ^ )
copyright symbol ( © )
currency generic: ( ¤ )
specific: ฿, ¢, $, , ƒ, , , , £, , ¥, , ,
daggers ( , )
degree ( ° )
ditto mark ( )
inverted exclamation mark ( ¡ )
inverted question mark ( ¿ )
number sign/pound/hash ( # )
numero sign ( )
ordinal indicator (º, ª)
percent (etc.) ( %, ‰, )
pilcrow ( )
prime ( )
registered trademark ( ® )
section sign ( § )
service mark ( )
sound recording copyright symbol ( )
tilde ( ~ )
trademark ( )
underscore/understrike ( _ )
vertical/broken bar, pipe ( |, ¦ )
Uncommon typography
asterism ( )
falsum ( )
index/fist ( )
therefore sign ( )
because sign ( )
interrobang ( )
irony mark/percontation point ( ؟ )
lozenge ( )
reference mark ( )
tie ( )

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 (per thousand) sign ‰ (Unicode: U+2030) and the permyriad (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.

Contents

Correct style

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Spacing

There is no consensus as to whether or not to include a space between the number and percent sign in English. Many authorities prescribe that there should be no space, whilst others typographically require one for various reasons; these include The International System of Units and the ISO 31-0 standard, while the TeX typesetting system encourages it.[1][2][3] 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 prescribe to write the number and percent sign without any space in between.[4]

The brochure of SI says in chapter 5: "a space separates the number and the symbol %"[5].

In some languages, however, there are specific rules of spacing in front of the percent sign. In Czech, for example, the percent sign is spaced if the number is used as a noun, while no space is inserted if the number is used as an adjective (e.g. "a 50% increase").[6] In Finnish, the percent sign is always spaced, and a case suffix can be attached to it using the colon (e.g. 50 %:n kasvu 'an increase of 50 %'). In French, the percent sign is also always spaced because the percent is considered as a unit. In traditional Russian typography there is a set rule to space it by 3 pt but it is not that common in Russia today.

Usage in text

It is often recommended that the percent sign is only used in tables and other places with space restrictions. In running text, it should be spelled out as percent. For example, not "Sales increased by 24% over 2006", but rather "Sales increased by 24 percent over 2006".[7][8][9].

Evolution

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").[10]

A different reference[11] 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, a solidus is used instead of the horizontal fraction bar.

Usage

In computers

Names for the percent sign include percent sign (in ITU-T), mod, grapes (in hacker jargon), and the humorous double-oh-seven (in INTERCAL). The ASCII code for the percent character is 37, or 0x25 in hexadecimal. 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.[12]

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).

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 therefore also in LaTeX) and PostScript, a % denotes a line comment.

In BASIC, a trailing % after a variable name marks it as an integer.

In Perl % symbol is for hashes.

In many programming languages' string formatting operations (performed by functions such as printf) the percent sign denotes parts of the template string that will be replaced with arguments. In old versions of Python (before 3), the percent sign is also used as the string formatting operator. [13]

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.  %0 stands for the specification of the batch file itself as typed on the command line. The % sign is also used similarly in the FOR command. %VAR1% represents the value of an environment variable named VAR1. Thus:

set PATH=c:\;%PATH%

sets a new value for PATH, that being the old value preceded by "c:\;". Because these uses give the percent sign special meaning, the sequence %% (two percent signs) is used to represent a literal percent sign, so that:

set PATH=c:\;%%PATH%%

would set PATH to the literal value "c:\;%PATH%".


In the C Shell, % is part of the default command prompt.

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.

See also

References

  1. ^ "The International System of Units". International Bureau of Weights and Measures. 2006. http://www.bipm.org/utils/common/pdf/si_brochure_8.pdf. Retrieved 2007-08-06.  
  2. ^ "Quantities and units – Part 0: General principles". International Organization for Standardization. 1999-12-22. http://www.iso.org/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=3621. Retrieved 2007-01-05.  
  3. ^ Heldoorn, Marcel (2002-08-01). "The SIunits package" (PDF). Comprehensive TeX Archive Network. http://www.ctan.org/tex-archive/macros/latex/contrib/SIunits/. Retrieved 2007-01-05.  
  4. ^ "The Chicago Manual of Style". University of Chicago Press. 2003. http://www.chicagomanualofstyle.org/. Retrieved 2007-01-05.  
  5. ^ "SI brochure". International Bureau of Weights and Measures. 2006. http://www.bipm.org/en/si/si_brochure/chapter5/5-3-7.html. Retrieved 2009-04-07.  
  6. ^ "Jazyková poradna ÚJČ AV ČR: FAQ". Ústav pro jazyk český Akademie věd ČR. 2002. http://www.ujc.cas.cz/poradna/odpo.html#12st. Retrieved 2009-03-16.  
  7. ^ American Economic Review: Style Guide
  8. ^ UNC Pharmacy style guide
  9. ^ University of Colorado style guide
  10. ^ Weaver, Douglas. "The History of Mathematical Symbols". http://www.roma.unisa.edu.au/07305/symbols.htm. Retrieved 2006-07-18.  
  11. ^ "U+0025 PERCENT SIGN". http://www.decodeunicode.org/U+0025.  
  12. ^ Thompson, Ken (1996). "Users' Reference to B". http://cm.bell-labs.com/cm/cs/who/dmr/kbman.html.  
  13. ^ "String Formatting Operations". http://docs.python.org/lib/typesseq-strings.html.  

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