This structure is used in the following IOCTL fns:
440dH 41H (write track on logical drive)
440dH 61H (read track on logical drive)

DvRq 13H  (generic IOCTL for block devices)

IoctlRdWrtTrackRec
Offset Size Contents
                                                                          
+0     1  rSpclFns     (always 00)
+1     2  wHead        head to read/write
+3     2  wTrack       track (cylinder) to read/write
+5     2  wStartSect   starting sector (0-based; sector 1=0, 2=1...)
+7     2  wSectCnt     sector count (0-based; use 8 for 9-sector track)
+9     4  fpBuff       32-bit addr of buffer containing data to write
(440dH 41H) or addr to hold data read (440dH 41H)
0dH (13)         size of an IoctlRdWrtTrackRec

Notes: The wStartSect field is relative to the start of the track (for
instance, to write an entire track on a 9-sector/track diskette,
set wStartSect to 0 and set wSectCnt to 9.

This is the only place I've seen where tracks are not specified
with their "hardware code" numbers (e.g. 1-9).

See Also: fn 440dH (Generic IOCTL for block devices)
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IoctlRdWrtTrackRec