секторы на флопаке

BPBRec
  Offset Size Contents
  ▀▀▀▀▀▀ ▀▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
   +0      2  wSectSize    bytes per sector (usually 512; 200H)
   +2      1  bClustSects  sectors per allocation unit (cluster)
   +3      2  wResSects    boot and reserved sectors
   +5      1  bFatCnt      number of File Allocation Tables.  See FAT.
   +6      2  wRootEntries max number of 32-byte DirEntryRecs in root
   +8      2  wTotSects    total number of sectors in media
                           0000H means >32 MB, so use lBigTotSects
 +0aH      1  bMedia       media descriptor (same as 1st byte in FAT)
 +0bH      2  wFatSects    number of sectors in one FAT
                           ───────────────────────── Extended BPB additions
 +0dH      2  wSectsPerTrk sectors per track
 +0fH      2  wHeads       number of read/write heads
 +11H      4  lHidSects    hidden sectors (ignore hiword in pre-DOS 4.0)
 +15H      4  lBigTotSects 32-bit TotSects in volume (partitions > 32M)
          25               Length of a BPBRec (was 13 in pre-DOS 4.0)