Disk status commands return status on the current disk in the opened unit.
These commands may be done with quick I/O and thus may be called within
interrupt handlers (such as the trackdisk disk change handler). See the
"Exec: Device Input/Output" chapter of the Amiga ROM Kernel Reference
Manual: Libraries for more detailed information on quick I/O.

 Determining The Presence Of A Disk 
 Determining The Write-Protect Status Of A Disk 
 Determining The Drive Type 
 Determining The Number Of Tracks Of A Drive 
 Determining The Current Diskchange Number