".dcmd" is a filename extension of "DiskCatalogMaker catalog with thumbnails" format.
The catalog file format is compatible with all editions of DiskCatalogMaker 5 or later.
How to read the format?
On Mac OS X:
DiskCatalogMaker (v5.5 or later) can read the file format. You can get the latest version of DiskCatalogMaker for Mac.
On other platforms:
There is no way to read the file format. You can export the contents as a text file using DiskCatalogMaker for Mac.