A DCF, short for Disk Copy Fast is a now outdated file archiving software that creates disk images from floppy drives.
DCF is the file format used to encode the image files, as well as the extension on the file.
All DCF files contain file headers and the raw image of the floppy disk. DCF is not compatible with IMA or IMG files.
The software was abandoned in 1996, and does not work well with Windows XP or higher.
To extract old DCF files, you can use WinImage.