Results 1 to 5 of 5  Thread: Bootsectors    1. #1     Senior
Member     Join Date     Jun 2003       Original here:     -[El
Half -]-       When you power on your computer the BIOS does a
Power On Self-Test     (POST). It then locates the first
bootable drive (as defined     by the boot sequence in the BIOS
menu).     Then the first sector on that drive is read (cylinder
0, sector 0)     and the instruction pointer (IP) is moved to
the start of this code.     The boot sector has just been loaded
into memory.     It is located at: 0000:7C00      All this is
done in 16-bit real mode.     16-bit meaning that we have a
16-bit address space and thus we can     address only up to up
to 0xFFFFF bytes (1024 kb) in memory.     Real mode means that
we have no restrictions (obviously).      When writing a
bootsector you have to keep in mind that you cannot     use OS
interrupts. But we can use int 10h which is offered by the BIOS
to do something "useful"!      A bootsector always has to end
with 0x55AA. In your code