Wildcard character

Also know as Asterisk (disambiguation) and * (disambiguation).

• An asterisk is a typographical symbol or glyph.
• The * comes from Late Latin asteriscus, from Ancient Greek ἀστερίσκος, asteriskos, "little star". It is so called because it resembles a conventional image of a star.
• Computer scientists and mathematicians often vocalize it as star (as, for example, in the A* search algorithm or C*-algebra).
• In English, an asterisk is usually five-pointed in sans-serif typefaces, six-pointed in serif typefaces, and six- or eight-pointed when handwritten.
• It can be used as censorship.
• It is also used on the Internet to correct one's spelling, in which case it appears after or before the corrected word.

• In computer science, the asterisk is commonly used as a wildcard character, or to denote pointers, repetition, or multiplication.

Insights

Competitive sports and games

• In colloquial usage, an asterisk is used to indicate that a record is somehow tainted by circumstances, which are putatively explained in a footnote referenced by the asterisk. This usage arose after the 1961 baseball season in which Roger Maris of the New York Yankees broke Babe Ruth's 34-year-old single-season home run record. Because Ruth had amassed 60 home runs in a season with only 154 games, compared to Maris's 61 over 162 games, baseball commissioner Ford Frick announced that Maris' accomplishment would be recorded in the record books with an explanation (often referred to as "an asterisk" in the retelling). In fact, Major League Baseball had no official record book at the time, but the stigma remained with Maris for many years, and the concept of a real or figurative asterisk denoting less-than-official records has become widely used in sports and other competitive endeavors. A 2001 TV movie about Maris' record-breaking season was called 61* (pronounced sixty-one asterisk) in reference to the controversy.
• In recent years, the asterisk has come into use on baseball scorecards to denote a "great defensive play."
• In February 2011 the United States Olympic Committee and the Ad Council launched an anti-steroid campaign called "Play Asterisk Free" aimed at teens. The campaign, whose logo uses a heavy asterisk, first launched in 2008 under the name Don't Be An Asterisk.

Barry Bonds

Fans critical of Barry Bonds, who has been accused of using performance-enhancing drugs during his baseball career, invoked the asterisk notion during the 2007 season, as he approached and later broke Hank Aaron's career home run record. Opposing fans would often hold up signs bearing asterisks whenever Bonds came up to bat. After Bonds hit his record-breaking 756th home run on August 7, 2007, fashion designer and entrepreneur Marc Ecko purchased the home run ball from the fan who caught it, and ran a poll on his Web site to determine its fate. On September 26, Ecko revealed on NBC's Today show that the ball will be branded with an asterisk and donated to the Baseball Hall of Fame. The ball, marked with a die-cut asterisk, was finally delivered to the hall on July 2, 2008 after Marc Ecko unconditionally donated the artifact rather than loaning it to the hall as originally intended.

Cricket

• In cricket, it signifies a total number of runs scored by a batsman without losing his wicket; e.g. 107* means '107 not out'. When written before a player's name on a scorecard, it indicates the captain of the team.
• It is also used on television when giving a career statistic during a match. For example, 47* in a number of matches column means that the current game is the player's 47th.

Computing

Computer science

• In computer science, the asterisk is used in regular expressions to denote zero or more repetitions of a pattern; this use is also known as the Kleene star or Kleene closure after Stephen Kleene.
• In the Unified Modeling Language, the asterisk is used to denote zero to many classes.

Computer interfaces

• In some command line interfaces, such as the Unix shell and Microsoft's CMD, the asterisk is the wildcard character and stands for any string of characters. This is also known as a wildcard symbol. A common use of the wildcard is in searching for files on a computer. For instance, if a user wished to find a document called Document 1, search terms such as Doc* and D*ment* would return this file. Document* would also return any file that begins with Document.
• In some graphical user interfaces an asterisk is pre- or appended to the current working document name shown in a window's title bar to indicate that unsaved changes exist. In Windows versions before XP the asterisk was also used as a mask to hide passwords being entered into a text box; later this was changed to a bullet.
• In Commodore (and related) filesystems, an asterisk appearing next to a filename in a directory listing denotes an improperly closed file, commonly called a "splat file."
• In travel industry Global Distribution Systems, the asterisk is the display command to retrieve all or part of a Passenger Name Record.
• In HTML web forms, an asterisk can be used to denote required fields.
• Chat Room etiquette calls on one asterisk to correct a misspelled word that has already been submitted. For example, one could post lck, then follow it with luck* to correct the word's spelling, or if it's someone else that notices the mistake, they would use *luck. Here's another example. The typo in trugger could go to trigger*. Template:Citation needed
  • Enclosing a phrase between two asterisks is used to denote an action the user is "performing", e.g. *pulls out a paper*, although this usage is also common on forums, and less so on most chat rooms due to /me or similar commands. Hyphens (-action-) and double colons (::action::) as well as the operator /me are also used for similar purposes.

Adding machines and printing calculators

• Some international models of adding machines and printing calculators use the asterisk to denote the total, or the terminal sum or difference of an addition or subtraction sequence, respectively, sometimes on the keyboard where the total key is marked with an asterisk and sometimes a capital T, and on the printout.

Programming languages

Many programming languages and calculators use the asterisk as a symbol for multiplication. It also has a number of special meanings in specific languages, for instance:

• In some programming languages such as the C, C++, and Go programming languages, the asterisk is used to dereference or to declare a pointer variable.
• In the Common Lisp programming language, the names of global variables are conventionally set off with asterisks, *LIKE-THIS*.
• In the Ada, Fortran, Perl, Python, Ruby programming languages, in some dialects of the Pascal programming language, and many others, a double asterisk is used to signify exponentiation: 5**3 is 5*5*5 or 125.
• In the Perl programming language, the asterisk is used to refer to the typeglob of all variables with a given name.
• In the programming languages Ruby and Python, * has two specific uses. First, the unary * operator applied to a list object inside a function call will expand that list into the arguments of the function call. Second, a parameter preceded by * in the parameter list for a function will result in any extra positional parameters being aggregated into a tuple (Python) or array (Ruby), and likewise in Python a parameter preceded by ** will result in any extra keyword parameters being aggregated into a dictionary.
• In the APL language, the asterisk represents the exponential and exponentiation functions.
• In IBM Job Control Language, the asterisk has various functions, including in-stream data in the DD statement, the default print stream as SYSOUT=*, and as a self-reference in place of a procedure step name to refer to the same procedure step where it appears.
• In Haskell, the asterisk represents the set of well-formed, fully applied types - that is a 0-ary kind of types.

Comments in computing

Main article: block comments

In the B programming language and languages that borrow syntax from it, like C, PHP, Java, or C#, comments (parts of the code not intended to be compiled into the program) are marked by an asterisk combined with the slash:

/* Here is a comment.
   The compiler will ignore it. */

Some Pascal-like programming languages, for example, Object Pascal, Modula-2, Modula-3, and Oberon, as well as several other languages including ML, Wolfram Language (Mathematica), AppleScript, OCaml, Standard ML, and Maple, use an asterisk combined with a parenthesis:

(* This is a comment.
   The compiler will ignore it. *)

CSS, while not strictly a programming language, also uses the slash-star comment format.

body {
  /* This ought to make the text more readable for far-sighted people */
  text-size:24pt;
}

Economics

• In economics, the use of an asterisk after a letter indicating a variable such as price, output, or employment indicates that the variable is at its optimal level (that which is achieved in a perfect market situation). For instance, p* is the price level p when output y is at its corresponding optimal level of y*.
• Also in international economics asterisks are commonly used to denote economic variables in a foreign country. So, for example, "p" is the price of the home good and "p*" is the price of the foreign good, etc.

Education

• In the GCSE and A-Level examinations in the United Kingdom and the PSLE in Singapore, A* ("A-star") is a special top grade that is distinguished from grade A.
• In the Hong Kong Diploma of Secondary Education (HKDSE) examination in Hong Kong, 5** (5-star-star) and 5* (5-star) are two special top grades that are distinguished from Level 5. Level 5** is the highest level a candidate can attain in HKDSE.

Fluid Mechanics

In fluid mechanics, an asterisk in superscript is sometimes used to mean a property at sonic speed.

Games

• Certain categories of character types in role-playing games are called splats, and the game supplements describing them are called splatbooks. This usage originated with the shorthand "*book" for this type of supplement to various World of Darkness games, such as Clanbook: Ventrue (for Vampire: The Masquerade) or Tribebook: Black Furies (for Werewolf: The Apocalypse), and this usage has spread to other games with similar character-type supplements. For example, Dungeons & Dragons Third Edition has had several lines of splatbooks: the "X & Y" series including Sword & Fist and Tome & Blood prior to the "3.5" revision, the "Complete X" series including Complete Warrior and Complete Divine, and the "Races of X" series including Races of Stone and Races of the Wild.
• In many MUDs and MOOs, as well as "male", "female", and other more esoteric genders, there is a gender called "splat", which uses an asterisk to replace the letters that differ in standard English gender pronouns. For example, h* is used rather than him or her. Also, asterisks are used to signify doing an action, for example, "*action*".
• Game show producer Mark Goodson used a six-pointed asterisk as his trademark. It is featured prominently on many set pieces from The Price Is Right.
• Scrabble players put an asterisk after a word to indicate that an illegal play was made.

Human genetics

• In human genetics, * is used to denote that someone is a member of a haplogroup and not any of its subclades (see * (haplogroup)).

Linguistics

In linguistics, an asterisk is placed before a word or phrase to indicate that it is not used, or there are no records of it being in use. This is used in several ways depending on what is being discussed.

Historical linguistics

In historical linguistics, the asterisk marks words or phrases that are not directly recorded in texts or other media, and that are therefore reconstructed on the basis of other linguistic material (see also comparative method).

In the following example, the Proto-Germanic word ainlif is a reconstructed form.

• *ainlif → endleofan → eleven

A double asterisk indicates a form that would be expected according to a rule, but is not actually found. That is, it indicates a reconstructed form that is not found or used, and in place of which another form is found in actual usage:

• For the plural, **kubar would be expected, but separate masculine plural akābir أكابر and feminine plural kubrayāt كبريات are found as irregular forms.

Generative linguistics

In generative linguistics, especially syntax, an asterisk in front of a word or phrase indicates that the word or phrase is not used because it is ungrammatical.

• wake her up / *wake up her (in Standard American English)

An asterisk before a parenthesis indicates that the lack of the word or phrase inside is ungrammatical, while an asterisk after the opening bracket of the parenthesis indicates that the existence of the word or phrase inside is ungrammatical.

• go *(to) the station - Here, "go the station" would be ungrammatical.
• go (*to) home - Here, "go to home" would be ungrammatical.

Ambiguity

Since a word marked with an asterisk could mean either "unattested" or "impossible", it is important in some contexts to distinguish these meanings. In general, authors retain asterisks for "unattested", and prefix ˣ, **, or a superscript "?" for the latter meaning.

Marketing

Asterisks (or other symbols) are commonly used in advertisements to refer readers to special terms/conditions for a certain statement, commonly placed below the statement in question. For example: an advertisement for a sale may have an asterisk after the word "sale" with the date of the sale at the bottom of the advertisement, similar to the way footnotes are used.

Mathematics

The asterisk has many uses in mathematics. The following list highlights some common uses and is not exhaustive.

stand-alone

• An arbitrary point in some set. Seen, for example, when computing Riemann sums or when contracting a simply connected group to the singleton set { Template:Unicode }.

as a unary operator, denoted in prefix notation

• The Hodge dual operator on vector spaces $*:A^{k}\rightarrow A^{n-k}$.

as a unary operator, written as a subscript

• The pushforward (differential) of a smooth map f between two smooth manifolds, denoted f_{Template:Unicode}.
• And more generally the application of any covariant functor, where no doubt exists over which functor is meant.

as a unary operator, written as a superscript

• The complex conjugate of a complex number (the more common notation is $\bar{z}$).
• The conjugate transpose, Hermitian transpose, or adjoint matrix of a matrix.
• Hermitian adjoint.
• The multiplicative group of a ring, especially when the ring is a field. E.g. $\mathbb {C} ^{*}=\mathbb {C} -\{0\}.$
• The dual space of a vector space V, denoted V*.
• The combination of an indexed collection of objects into one example, e.g. the combination of all the cohomology groups H^k(X) into the cohomology ring H*(X).
• In statistics, z* and t* are given critical points for z-distributions and t-distributions, respectively.

as a binary operator, in infix notation

• A notation for an arbitrary binary operator.
• The free product of two groups.
• f Template:Unicode g is a convolution of f with g.

The asterisk is used in all branches of mathematics to designate a correspondence between two quantities denoted by the same letter – one with the asterisk and one without.

Mathematical typography

In fine mathematical typography, the Unicode character Template:Unichar (in HTML, ∗) is available. This character also appeared in the position of the regular asterisk in the PostScript symbol character set in the Symbol font included with Windows and Macintosh operating systems and with many printers. It should be used in fine typography for a large asterisk that lines up with the other mathematical operators.

Music

• In musical notation the sign indicates when the sustain pedal of the piano should be lifted.
• In liturgical music, an asterisk is often used to denote a deliberate pause.

Religious texts

• In the Geneva Bible and the King James Bible, an asterisk is used to indicate a marginal comment or scripture reference.
• In the Leeser Bible, an asterisk is used to mark off the seven subdivisions of the weekly Torah portion. It is also used to mark the few verses to be repeated by the reader of the Haftara.
• In American printings of the Book of Common Prayer, an asterisk is used to divide a verse of a Psalm in two portions for responsive reading. British printings use a spaced colon (" : ") for the same purpose.

Star of Life

Replacement for cross/crescent/star on ambulances.

Ambulance in Lausanne

World War I ambulance

Statistical results

In many scientific publications, the asterisk is employed as a shorthand to denote the statistical significance of results when testing hypotheses. When the likelihood that a result occurred by chance alone is below a certain level, one or more asterisks are displayed. Popular significance levels are <0.05 (*), <0.01 (**), and <0.001 (***).