Database created in versions of 4D prior to 2004 on Mac OS are often comprised of two files; the structure file and the data file:



Databases created in 4D 2004 are made up of 4 files:



In fact older, 2-file database contain the same information. The structure resources are in the "resource fork" of the structure file and the data resources are in the resource fork of the data file. For more information on data and resource forks see:

https://developer.apple.com/documentation/mac/MoreToolbox/MoreToolbox-11.html

In order to move a Mac OS database to Windows in previous versions of 4D it was necessary to use the 4D Transporter application (or another comparable application) to "split" the resource forks out of the Mac files. This is necessary because, in most cases, the resource fork of the files will be lost when copying to Windows. The result was a 4-file database that could be used on either platform.

There is no version of 4D Transporter for 4D 2004. In order to split the resources for a 4D 2004 database that is still a 2-file database, 4D Tools can be used. The "repair" or "compact" option in 4D Tools can be used to split both the structure file and data file into their component parts. Note that 4D Tools will create 4 new files, rather than modifying the original files. The new, 4-file database can be copied back and forth from Mac OS to Windows without the worry of stripping the resources.