To apeman(网络猩猩),
The DOS-C source code describled everything about how to boot from disc.
Don't you have DOS-C source code ? The file boot.asm will tell you everything.
You can also get information from DR-DOS.
BIOS loads boot sector(0 head, 0 cilynder, 0 Sector. if you boot from a floppy disk) to physical addresss 0x07c00. Then PC will excute instructions from 0x07c00. DOS first looks for io.sys, if found, loads it. io.sys looks for msdos.sys, if found loads it, msdos.sys looks for command.exe, if found, loads it.
这些问题不是一两句话就可以说得清楚的。你最好找一本书看看。
Disk Partition Table (Fixed disk boot record)
Offset Represents: (see format below)
01BE Partition 1 data table (16 bytes)
01CE Partition 2 data table (16 bytes)
01DE Partition 3 data table (16 bytes)
01EE Partition 4 data table (16 bytes)
01FE Signature (hex 55 AA, 2 bytes)
Offset from beginning of partition data shown above:
Offset Size Description
00 byte boot indicator
01 byte beginning sector head number
02 byte beginning sector (2 high bits of cylinder #)
03 byte beginning cylinder# (low order bits of cylinder #)
04 byte system indicator
05 byte ending sector head number
06 byte ending sector (2 high bits of cylinder #)
07 byte ending cylinder# (low order bits of cylinder #)
08 dword number of sectors preceding the partition
0B dword number of sectors in the partition
00 - unknown operating system
01 - DOS with 12 bit FAT, 16 bit sector number
02 - XENIX
04 - DOS with 16 bit FAT, 16 bit sector number
05 - DOS Extended partition (DOS 3.3+)
06 - DOS 4.0 (Compaq 3.31), 32 bit sector number
51 - Ontrack extended partition
64 - Novell
75 - PCIX
DB - CP/M
FF - BBT
Signature
Hex 55AA marks the end of valid boot sector. This is also
required in each of the partition boot records.