You are referring to partition tables. The first 512 byte sector contains the following:
master boot record: 446bytes of boot code
primary partition table: 64 bytes ( 4 entries, 16 bytes each)
"signature": 2 bytes (55aa hex)
If the disk has more than 4 partitions, then one of the primary entries will describe an "extended" partition. The partition tables for "logical partitions" ---which are tied to the extended partition---are elsewhere on the drive.
Here is a useful link:
To copy data like this, use the low-level routine--"dd" For example, to copy the first 512 byte sector described above:
dd if=/dev/hda of=<filename> bs=512 count=1 (assumes that your drive is hda)