I first zeroed out the first 512 bytes of the USB flash drive using
dd if=/dev/zero of=/dev/sdb bs=512 count=1
Then i saw that the output of
hexdump -n 512 /dev/sdb
and from within fdisk (the raw dump of the partition table) is different.
Specifically, hexdump shows that all bytes are really zeroed out. But, in fdisk I see that the 441-444th bytes have random values each time you restart fdisk. Also, the last 2 bytes have the boot signature AA55. This boot signature doesn't change each time i restart fdisk. All the other bytes are zeroed out even in fdisk.
Why this discrepancy?