Distribution Media Format
Distribution Media Format (DMF) is a formatting standard for IBM PC diskettes. The format used for 3½ " floppy disks differs from the standard format mainly in that 21 sectors are used per track instead of 18 sectors. This means that 16.7% more data can be used, a total of around 1.68 MB instead of the usual 1.44 MB can be saved on 3½ "floppy disks.
Since only a few programs can create DMF disks, the format also serves as a copy protection .
The DMF format was mainly used by Microsoft , for example for the Windows 95 installation disks .