Appledouble header file
A separate file in a filesystem containing the Apple resource fork for a related data file, developed by Apple for A/UX and therefore compatible with other filesystems including those mounted remotely. They are heavily used under Mac OS X.
This file is named the same as the data file, with "
._" prepended to
the original name. These header files are automatically included in ZIP
files under a hierarchy starting with "
__MACOSX" when utilizing the
Finder's "Archive as..." function.
http://users.phg-online.de/tk/netatalk/doc/Apple/v1/ from "A/UX Toolbox: Macintosh ROM Interface manual", Chapter 6 File Systems and File Formats
identifies the magic number
0x00051607 for AppleDouble files as the
first 4 bytes in the file
http://en.wikipedia.org/wiki/AppleDouble background and additional information
http://www.ietf.org/rfc/rfc1740.txt MIME Encapsulation of Macintosh files - MacMIME