HelpPC 2.10 Quick Reference Utility Copyright 1991 David Jurgens

                         Boot Sector (since DOS 2.0)

    Offset  Size               Description

       00   3bytes     jump to executable code
       03   8bytes     OEM name and version
       0B   word       bytes per sector
       0D   byte       sectors per cluster (allocation unit size)
       0E   word       number of reserved sectors (starting at 0)
       10   byte       number of FAT's on disk
       11   word       number of root directory entries (directory size)
       13   word       number of total sectors (0 if partition > 32Mb)
       15   byte       media descriptor byte  (see MEDIA DESCRIPTOR)
       16   word       sectors per FAT
       18   word       sectors per track  (DOS 3.0+)
       1A   word       number of heads  (DOS 3.0+)
       1C   word       number of hidden sectors  (DOS 3.0+)
       20   dword      (DOS 4+) number of sectors if offset 13 was 0
       24   byte       (DOS 4+) physical drive number
       25   byte       (DOS 4+) reserved
       26   byte       (DOS 4+) signature byte (29h)
       27   dword      (DOS 4+) volume serial number
       2B  11bytes     (DOS 4+) volume label
       36   8bytes     (DOS 4+) reserved

       - implementation format not guaranteed in all OEM DOS releases
       - BIOS expects a boot sector of 512 bytes
       - DOS 3.2 began reading BIOS Parameter Block (BPB) information from
         the boot sector, previous versions used only the media byte in FAT
       - DOS 4.x added offsets 20-3Dh and offset 20h determines the number
         of sectors if offset 13h is zero
       - hard disks have a master boot record and partition boot records;
         the master boot record and Disk Partition Table (DPT) share the
         same sector

Esc or Alt-X to exit boot sector Home/PgUp/PgDn/End ←↑↓→
Converted to HTML in 2006 by Timo Bingmann