The type attribute of a file is unique to the Macintosh file system.
A file's type:
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is always a four-byte (character) code such as 'TEXT'. |
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Even file types that appear to contain less than four characters when displayed actually have four. The file type of an Abobe Acrobat PDF file appears to be 'PDF', but is actually 'PDF ', where the last character is a space. |
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Most file types 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 because the file was not given the correct file type when it was created on your computer. Files downloaded from the web, received via e-mail, or copied from a non-Macintosh computer may not have their file types set correctly. |
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is only a kind of label, and does not determine the file's format. This means that changing the file type of a file does not affect the contents of a file or the format of its data. |
When set correctly, a file's type:
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can be used by applications to determine if the file should be displayed in file selection windows. |
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tells applications the format of the file's contents. |
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is used in conjunction with the file's creator signature to determine what icon should be displayed in the Finder. |
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is used by the Finder to determine if applications should hilite when the file is dragged onto the application's icon. |