The MBR

The MBR(Master Boot Record) is the very first sector of a physical disk(not a floppy). If this disk is the disk of which the system will boot, this sector is also the very first sector that is being loaded to memory, and executed. This is done by the bios at startup. Because of this, this sector has to start with valid 80x86 code. This can be a few things, it can be the Linux Bootloader, Lilo, the windows bootloader -OR- the V2_OS Bootloader, or something completely different. Note that a sector is just 512 bytes, so it's first task is too study the disk, and see if it can load more sectors and pass control to them. This is done through the partition table.
When the MBR code has scanned the partition table and found a partition marked as active, it positions the HD-heads, loads the first sector of that partition into memory, and executes it. This first sector of a partition is called a 'BootSector'. The MBR is free to choose a location for this BootSector.

The MBR of the V2_FS does not necessarily have to be the V2_OS MBR as long as this MBR performs all task described above, and has a valid partitiontable, and does not rely on extra sectors.


The MBR Format:

Offset Description
0000h 1BEh 80X86 code to locate a bootable partition from the partitiontables(possibly on other disks too), load it, and execute it.
01BEh 10h Partition Table Entry #1
01CEh 10h Partition Table Entry #2
01DEh 10h Partition Table Entry #3
01EEh 10h Partition Table Entry #4
01FEh 2 MBR Signature AA55h

Partition Table Entry:

Offset Description
0000h 1h 80h means this partition has a valid BootSector. 0h means it has not.(This field corresponds to the 'active' option in fdisk under dos/windows)
0001h 1h First Head of this sector
0002h 1h First Sector of this partition
0003h 1h First Cylinder of this sector
0004h 1h FileSystem Indicator. 33h for V2_FS, for other ID's, click here
0005h 1h Last Head of this sector
0006h 1h Last Sector of this partition
0007h 1h Last Cylinder of this partition
0008h 4h DWord relative(Absolute) starting sector
000Ch 4h DWord relative(Absolute) starting sector

Extended partitions:
Some filesystems support 'Extended partitions'. This means that on the bootsector of this partition, there is no 80x86 code, but another MBR Structure, including another partition table ! Extended partitions can therefore never be Bootable or Active.

NOTE: The V2_OS MBR is not available yet, but you can use any other MBR just the same...