OSDev.org

I try to make a OS but I'm allmost bold!!
I compile my files with FASM the only tool i've got is DEBUG.EXE tot write to SECTOR 0

When I load a file it starts with offset 100 so i have FDH bytes to make my bootloader or OS.

COPY FILE TO DOS BOOT USB
THEN BOOT FROM DOS
START "DEBUG.EXE OS.COM"
MAKE CHANGES FOR THE BIOS LOADER TO UNDERSTAND IT IS A BOOTABLE.
CHANGE USB.
W 0 2 0 1
REBOOT
AND SEE THE NEXT LITTLE TEST I DID, WORKED (OR NOT)

Is there a tool that loads a EXE or COM in memory and write it with offset 0 to SECTOR 0 of a (other) DISK??

Man, your question is on one side and the TOPIC is on the other side.
Advice: Edit your Topic as not to go unnoticed.

Sorry dudes,.. Had to post it before i was bold.
But finaly I made my own tool and it works fine.

But thanks fot the replay.

Now i've got your attention. Is the 55AA at [0FEH] only because Microsoft or can I set it at [FFFEH]?

Holus wrote:Sorry dudes,.. Had to post it before i was bold.
But finaly I made my own tool and it works fine.

But thanks fot the replay.

Now i've got your attention. Is the 55AA at [0FEH] only because Microsoft or can I set it at [FFFEH]?

No you cannot. 55AA is the boot signature. It's simply a signal to the BIOS that this media is bootable. It must be there at offset 0x1FE at the bootsector.Some BIOS may ignore this signature but it is always wise to put it there for compatibility.

Best Regards,
Chandra

I understand it now. Little bit late!! These are the last 2 byte of the first sector. 512 bytes = 200H bytes. The BIOS only loads 1 sector in memory.

It is a little bit old fashion to do this I think.
I hoped BIOS just stop loading till he found the signature, but that is not the case.

Thanks.