Disk Drive Functions

 19H query DOS default disk           0eH select DOS default disk
 47H query current default directory  3bH set default directory
 2fH query DTA (Disk Transfer Addr)   1aH set DTA
 54H query disk verify status         2eH set disk verify status

 36H get total and free disk space
 32H get DPB disk info                1bH 1cH get disk info 

 3305H query ID of boot drive

 0dH reset disk (flush buffers)       DS IOCTL 'F' flush DoubleSpace cache
                                      DS IOCTL 'I' invalidate Dblspace cache
 INT 13H BIOS Disk services
 INT 24H critical error handler address
 INT 25H/26H DOS direct disk read/write

 DoubleSpace API (see if disk is compressed, swap IDs, real free space,etc.)

 440dH 60H get device parameters      440dH 40H set device parameters
 440dH 61H read track                 440dH 41H write track
 440dH 62H verify track               440dH 42H format and verify track
 440dH 66H query media ID             440dH 46H set media ID
 440dH 68H sense media type

 4408H removable media query
 440eH get logical drive              440fH set logical drive
 4411H query IOCTL device
 INT 13H BIOS disk I/O                        Service Groups   DOS Functions