| Bit | Meaning when set |
|---|---|
| 0 | Not changed |
| 1 | Maybe changed |
| 2 | Changed |
| 3 | Empty |
| 4 | Ready |
| 5 | Drive is 40 track |
| 6 | Empty works |
| 7 | Changed works |
| 8 | Disc in drive is high density |
| 9 | Density sensing works |
| 10 | Ready works |
| 11 – 31 | Reserved, must be zero |
Exactly one of the bits 0-3 must be set. Once bit 6 or 7 is returned set for a given drive, they must always be so.