Distribution Media Format
Distribution Media Format is a format for floppy disks that Microsoft used to distribute software. It allowed the disk to contain 1680 KiB of data on a 3-inch disk, instead of the standard 1440 KiB. As a side effect, utilities had to specifically support the format in order to read and write the disks, which made copying of products distributed on this data storage medium more difficult. An Apple Macintosh computer running Disk Copy 6.3.3 on Mac OS 7.6 or later can copy and make DMF disks. The first Microsoft software product that uses DMF for distribution were the "c" revisions of Office 4.x. It also was the first software product to use CAB files, then called "Diamond".
Comparison of standard 1440 KiB and DMF 3-inch diskettes:
| Feature | Standard | DMF |
| Tracks | 80 | 80 |
| Sectors per track | 18 | 21 |
| Cluster size, in bytes | 512 | 1024 or 2048 |
| Root directory entries | 224 | 16 |
DMF, in the form of a 1680 KiB Virtual Floppy Disk image, and IBM Extended Density Format images are supported by Windows Virtual PC.