The creator signature (or just "creator") attribute of a file is unique to the Macintosh file system.
A file's creator signature:
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is always a four-byte (character) code such as 'FBud'. |
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Even creator signatures that appear to contain less than four characters when displayed actually have four. |
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Most creator signatures consist of four normal printing characters, but this is not required. |
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is not visible without the use of a utility such as File Buddy, ResEdit, or other program. |
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can be changed by a program such as File Buddy, most often to change the application used to open the file from the Finder. Files downloaded from the web, received via e-mail, or copied from a non-Mac computer may not have their creators set correctly and hence fail to open when double-clicked. |
When set correctly, a file's creator signature:
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is used by the Finder to determine what application should open the file when the file is opened from the Finder. |
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is used in conjunction with the file's type to determine what icon should be displayed in the Finder. |