If you are an old Mac hand, as, young and vital as I am, I seem to be, you may have odd old files lying around, possibly on floppies.
Assuming you can get them onto your Mac OS X system (floppies? How…1984), you may find they are unreadable. You might even find they are labeled “DD”. Stuffit Expander doesn’t know how to deal with them. However, it turns out you can trust that backwards compatibility on a Mac will actually rival Windows.
Go to ye olde HyperArchive, a site you may dimly recall from the mists of time. Find the line that says:
Abstract of dd-expand-40.sea.hqx 181K (12/20/1993) Download
And click the “Download” link. Yes, the file date is 1993, and yes, that’s a 181K file. That app will browse your filesystem to this day and expand any DiskDoubler archive. This is what we used before hard drives were cheap. It used the LZW compression algorithm, apparently, which is why open source tools don’t decode it. It is now basically abandonware by Symantec. Thanks, Symantec.
But anyway, this file from 12 years ago opens and runs just fine in emulation, and it managed to get a bunch of my old files recovered.