Beginning with System 1, Macintosh operating systems have attached type codes and creator codes as part of the file metadata. These four-character codes were designed to specify both the application that created the file (the creator code) and the specific type of the file (the type code) so that other applications could easily open and process the file data.
Macintosh operating systems use file metadata, including creator codes and type codes, to identify the application that created a file and its specific type. These four-character codes facilitate other applications in opening and processing the file data.