Alias (Mac OS)

In System 7 and later, an alias is a small file that represents another object in the file system.

Related Topics:
System 7 - File system

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A typical alias is small, between 1 and 5 KB. It acts as a stand-in for any object in the file system, such as a document, an application, a folder, a hard disk, a network share or removable medium or a printer. When double-clicked, the computer will act the same way as if the original file had been double-clicked. Likewise, choosing an alias file from within a 'File Open' dialog box would open the original file. The purpose of an alias is to assist the user in managing large numbers of files by providing alternative ways to access them without having to copy the files themselves.

Related Topics:
Document - Application - Folder - Hard disk - Network share - Printer - Dialog box

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An alias is a dynamic reference to an object. The original may be moved to another place in the file system, without breaking the link. The operating system stores several pieces of information about the original in the resource fork of the alias file. Examples of the information used to locate the original are:

Related Topics:
Operating system - Resource fork

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• path
• file ID
• directory ID
• name
• file size

Since any of these properties can change behind the OS' back as a result of user activity, various search algorithms are used to find the most plausible target. This fault-tolerance sets the alias apart from similar functions in other operating systems, such as the Unix symbolic link or the Microsoft Windows shortcut, at the expense of increased complexity. For example, an application can be moved from one directory to another, but an existing alias would still launch the same application when double-clicked.

Related Topics:
Unix - Symbolic link - Microsoft Windows

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Alias (Mac OS): Distinguishing marks ►