"?", ASCII character 63.

Common names: query; ITU-T: question mark; ques. Rare: whatmark; INTERCAL: what; wildchar; huh; hook; buttonhook; hunchback.

Question mark is used, along with colon for C's lazy triadic "if" operator (similar to the IIF function in Visual Basic). The expression x?y:z evaluates x, then if x is true it returns y else it returns z.

In Unix shell file name patterns, question mark matches any single character.