The symbol is sometimes thought to originate from the Latin quaestiō (that is, qvaestio), meaning "question", which was abbreviated during the Middle Ages to Qo. The uppercase Q was written above the lowercase o, and this mark was transformed into the modern symbol.
Another hypothesis about the origin of the question mark proposes that it originated in the 9th century, when it appeared as an exclamation point with a curved bar (like a tilde written slantwise) in order to reflect the intonation of the speaker. Lynne Truss attributes an early form to Alcuin of York. Truss describes the punctus interrogativus of the late 700s as "a lightning flash, striking from right to left." The name "question mark" was coined in the late 1800s.
Yet another view is that the question mark simply inverts the semicolon, which marked interrogative clauses in Ancient Greek (while enlarging the upper portion).
The origin of the question mark has also been associated with early musical notation like neumes. 
An American superstition that movies or television shows with question marks in the title do poorly at the box office has made many studios shy away from the punctuation mark. This has caused many works to be retitled when adapted for American cinema, such as the book Who Censored Roger Rabbit?, which was retitled Who Framed Roger Rabbit (without the question mark) for the big screen.
In some languages, such as Spanish and Galician, typography since the 18th century has required opening and closing question marks, as in "¿Qué hora es?" (What time is it?); an interrogative sentence or phrase begins with an inverted question mark (¿) and ends with the question mark (?). This orthographical rule is often disregarded in quick typing, although its omission is always considered a mistake.
In Greek and Church Slavonic, a semicolon (;) is used as a question mark.
In Armenian the question mark (՞ ) has a form of an open circle and is placed over the last vowel of the question word.
In Arabic, which is written from right to left, the question mark "؟" is mirrored right-to-left from the English question mark. (Some browsers may display the character in the previous sentence as a forward question mark due to font or text directionality issues.) Hebrew is also written right-to-left, but uses a question mark that appears on the page in the same orientation as the English "?".
The question mark is also used in modern writing in Chinese, Korean, and Japanese, though it is not always required in Japanese. Usually it is written as fullwidth form (?; Unicode: U+FF1F) in Chinese and Japanese. Japanese sentences that are a question will usually end with the sound "ka," in addition to having a rising intonation. Such sentences will typically omit the question mark.
Rhetorical questions in some (informal) situations can use a bracketed question mark, eg. "Oh, really(?)", for example in 888 subtitles.
Some have adapted the question mark into various irony marks, but these are very rarely seen.
The question mark can also be used as a "meta" sign to signal uncertainty regarding what precedes. It is usually put between brackets (?). The uncertainty may concern either a superficial (unsure spelling) or a deeper (truth, real meaning) level.
The question mark is often utilized as a wildcard character: a symbol that can be used to substitute for any other character or characters in a string. In particular "?" is used as a substitute for any one character as opposed to the asterisk, "*", which can be used as a substitute for zero or more characters in a string. The inverted question mark corresponds to Unicode code-point 191 (U+00BF), and can be accessed from the keyboard in Microsoft Windows on the default US layout by pressing Shift-/ or by holding down the Alt key and typing either 1 6 8 (ANSI) or 0 1 9 1 (Unicode) on the numeric keypad. In GNOME applications, it can be entered by typing the hexadecimal Unicode character while holding ctrl-shift, i.e.: ctrl-shift BF - ¿. In recent XFree86 and X.Org incarnations of the X Window System, it can be accessed as a compose sequence of two straight question marks, i.e. pressing The question mark is used in ASCII renderings of the International Phonetic Alphabet, such as SAMPA in place of the glottal stop symbol, ʔ, (which resembles "?" without the dot), and corresponds to Unicode code point U+0294, Latin letter glottal stop. In computer programming, the symbol "?" has a special meaning in many programming languages. In C, "?" is part of the ?: operator, which is used to evaluate simple boolean conditions. In C# 2.0, the "?" modifier and the "??" operator are used to handle nullable data types. In the POSIX syntax for regular expressions, such as the one used in Perl and Python, ? stands for "zero or one instance of the previous subexpression", i.e. an optional element. In many web browsers, "?" is used to show a character not found in the program's character set. This commonly occurs for apostrophes and quotation marks when they are written with software that uses its own proprietary non-standard code for these characters. Some fonts will instead use the Unicode Replacement Glyph (U+FFFD, �), which is commonly rendered as a white question mark in a black diamond. The generic URL syntax allows for a query string to be appended to a resource location in a web address so that additional information can be passed to a script; the query mark, ?, is used to indicate the start of a query string. A query string is usually made up of a number of different field/value pairs, each separated by the ampersand symbol, &, as seen in this url: Here, a script on the page login.php on the server www.example.com is to provide a response to the query string containing the pairs "username=test" and "password=blank".
The Batman anti-hero Riddler wears costumes including a green leotard decorated with question marks and a suit with a tie embellished with a single question mark on it. The DC hero Question (comics) often uses the question mark as a symbol and leaves notes with a "?" on them to show he was involved.
http://www.example.com/login.php?username=test&password=blankLinguistics
In linguistics, the question mark is prepended to strings to show that the linguist cannot determine whether they are well-formed or not. It is used similarly to the asterisk, which marks strings that are clearly ill-formed. It may be doubled to show greater uncertainty, or combined with the asterisk to show that the string is most likely ill-formed but that there is room for doubt.
Chess
In algebraic chess notation, "?" denotes a bad move, and "??" a blunder, "?!" a dubious move and "!?" an interesting move. For details of all of the chess punctuation see punctuation (chess).
Mathematics
In mathematics "?" commonly denotes Minkowski's question mark function.
Comics, cartoons and emoticons
In comic vignettes and strips, in cartoons and in anime, the symbol "?" over a character's head denotes ignorance, doubt or the sudden surprise of the subject, and with the same meaning is used with emoticons.See also
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