The term wildcard character has the following meanings:
- In high-frequency (HF) radio automatic link establishment, the wildcard character "?" may be substituted for any one of the 36 characters, "A" through "Z" and "0" through "9."
- Whether the wildcard character represents a single character or a string of characters must be specified.
Files and directories 
When specifying file names (or paths) in CP/M, DOS, Microsoft Windows and Unix-like operating systems, the asterisk character ("*") substitutes for zero or more characters. In Unix-like operating systems, the question mark ("?") substitutes for exactly one character, whereas in DOS, it substitutes for one character or less. For example, in DOS, the pattern 123??? will match 1231 or 12313 but not 1239919991. In Unix shells and Windows PowerShell, ranges of characters enclosed in square brackets ("[" and "]") substitute for all the characters in their ranges; for example, [A-Za-z] substitutes for any single capitalized or lowercase letter. Unix shells allow negation of the specified characters within brackets by using a leading "!". Matching wildcard patterns to multiple files or paths is referred to as glob expansion.
In SQL, wildcard characters can be used in "LIKE" expressions; the percent sign (%) matches zero or more characters, and underscore (_) a single character. Transact-SQL also supports square brackets ("[" and "]") to list sets and ranges of characters to match, a leading ^ matches only a character not specified within the brackets. In Microsoft Access, wildcard characters can be used in "LIKE" expressions; the asterisk sign (*) matches zero or more characters, and question mark (?) a single character.
Regular expressions 
See also 
- This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C" (in support of MIL-STD-188).