In
telecommunicationTelecommunication is transmission over a distance for the purpose of communication. In earlier times, this may have involved the use of smoke signals, drums, semaphore, flags or heliograph. In modern times, telecommunication typically involves the use of electronic devices such as the telephone,...
s, a
wildcard character is a
characterIn computer and machine-based telecommunications terminology, a character is a unit of information that roughly corresponds to a grapheme, grapheme-like unit, or symbol, such as in an alphabet or syllabary in the written form of a natural language....
that may be substituted for any of a defined subset of all possible characters.
- In high-frequency (HF) radio
Radio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
automatic link establishmentAutomatic Link Establishment, commonly known as ALE, is the worldwide de facto standard for digitally initiating and sustaining HF radio communications. ALE is a feature in an HF communications radio transceiver system, that enables the radio station to make contact, or initiate a circuit, between...
, 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
In mathematics, a string is an sequence of symbols that are chosen from a set or alphabet.In computer programming, a string is, essentially, a sequence of characters...
of characters must be specified.
In
computerA computer is a machine that manipulates data according to a set of instructions.Although mechanical examples of computers have existed through much of recorded human history, the first electronic computers were developed in the mid-20th century . These were the size of a large room, consuming as...
(software) technology, a
wildcard character can be used to substitute for any other character or characters in a string.
When specifying file names (or paths) in
CP/MCP/M is an operating system originally created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...
,
DOSDOS, short for "Disk Operating System", is a shorthand term for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions Windows 95, 98, and ME.Related systems...
,
Microsoft WindowsMicrosoft Windows is a series of software operating systems and graphical user interfaces produced by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces...
and
Unix-likeA Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
operating systemAn operating system is an interface between hardware and user which is responsible for the management and coordination of activities and the sharing of the resources of the computer that acts as a host for computing applications run on the machine. As a host, one of the purposes of an operating...
s,
the asterisk character ("*")An asterisk is a typographical symbol or glyph. It is so called because it resembles a conventional image of a star. Computer scientists and mathematicians often pronounce it as star...
substitutes for any zero or more characters, and the
question markThe question mark , also known as an interrogation point, interrogation mark, question point, query, or eroteme, is a punctuation mark that replaces the period at the end of an interrogative sentence...
(?) substitutes for any one character.
Telecommunication
In
telecommunicationTelecommunication is transmission over a distance for the purpose of communication. In earlier times, this may have involved the use of smoke signals, drums, semaphore, flags or heliograph. In modern times, telecommunication typically involves the use of electronic devices such as the telephone,...
s, a
wildcard character is a
characterIn computer and machine-based telecommunications terminology, a character is a unit of information that roughly corresponds to a grapheme, grapheme-like unit, or symbol, such as in an alphabet or syllabary in the written form of a natural language....
that may be substituted for any of a defined subset of all possible characters.
- In high-frequency (HF) radio
Radio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
automatic link establishmentAutomatic Link Establishment, commonly known as ALE, is the worldwide de facto standard for digitally initiating and sustaining HF radio communications. ALE is a feature in an HF communications radio transceiver system, that enables the radio station to make contact, or initiate a circuit, between...
, 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
In mathematics, a string is an sequence of symbols that are chosen from a set or alphabet.In computer programming, a string is, essentially, a sequence of characters...
of characters must be specified.
Computing
In
computerA computer is a machine that manipulates data according to a set of instructions.Although mechanical examples of computers have existed through much of recorded human history, the first electronic computers were developed in the mid-20th century . These were the size of a large room, consuming as...
(software) technology, a
wildcard character can be used to substitute for any other character or characters in a string.
Files and directories
When specifying file names (or paths) in
CP/MCP/M is an operating system originally created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...
,
DOSDOS, short for "Disk Operating System", is a shorthand term for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions Windows 95, 98, and ME.Related systems...
,
Microsoft WindowsMicrosoft Windows is a series of software operating systems and graphical user interfaces produced by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces...
and
Unix-likeA Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
operating systemAn operating system is an interface between hardware and user which is responsible for the management and coordination of activities and the sharing of the resources of the computer that acts as a host for computing applications run on the machine. As a host, one of the purposes of an operating...
s,
the asterisk character ("*")An asterisk is a typographical symbol or glyph. It is so called because it resembles a conventional image of a star. Computer scientists and mathematicians often pronounce it as star...
substitutes for any zero or more characters, and the
question markThe question mark , also known as an interrogation point, interrogation mark, question point, query, or eroteme, is a punctuation mark that replaces the period at the end of an interrogative sentence...
(?) substitutes for any one character. In
Unix shellA Unix shell is a command-line interpreter and script host that provides a traditional user interface for the Unix operating system and for Unix-like systems...
s and
Windows PowerShellWindows PowerShell is an extensible automation engine, consisting of a command-line shell and associated scripting language from Microsoft...
, 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. Matching wildcard patterns to multiple files or paths is referred to as glob expansion.
Databases
In
SQLSQL is a database computer language designed for managing data in relational database management systems , and originally based upon Relational Algebra. Its scope includes data query and update, schema creation and modification, and data access control. SQL was one of the first languages for...
, wildcard characters can be used in "LIKE" expressions; the percent sign (%) matches zero or more characters, and
underscoreThe underscore [ _ ] is a character that originally appeared on the typewriter. Prior to the advent of word processing, the underscore character was the only method of underlining words...
(_) a single character. In
Microsoft AccessMicrosoft Office Access, previously known as Microsoft Access, is a relational database management system from Microsoft that combines the relational Microsoft Jet Database Engine with a graphical user interface and software development tools...
, wildcard characters can be used in "LIKE" expressions; the
asteriskAn asterisk is a typographical symbol or glyph. It is so called because it resembles a conventional image of a star. Computer scientists and mathematicians often pronounce it as star...
sign (*) matches zero or more characters, and
question markThe question mark , also known as an interrogation point, interrogation mark, question point, query, or eroteme, is a punctuation mark that replaces the period at the end of an interrogative sentence...
(?) a single character.
Regular expressions
In many
regular expressionIn computing, regular expressions provide a concise and flexible means for identifying strings of text of interest, such as particular characters, words, or patterns of characters...
implementations, the
periodA full stop or period is the punctuation mark commonly placed at the end of several different types of sentences in English and many other languages...
(.) is the wildcard character for a single character.
External links