GUID Partition Table(GPT)

GPT header format (From Wiki)
Offset	Length	Contents
+0	8 bytes	Signature ("EFI PART", 45h 46h 49h 20h 50h 41h 52h 54h)
+8	4 bytes	Revision (for GPT version 1.0 (through at least UEFI version 2.3.1), the value is 00h 00h 01h 00h)
+12	4 bytes	Header size in little endian (in bytes, usually 5Ch 00h 00h 00h meaning 92 bytes)
+16	4 bytes	CRC32 of header (offset +0 up to header size), with this field zeroed during calculation
+20	4 bytes	Reserved; must be zero
+24	8 bytes	Current LBA (location of this header copy)
+32	8 bytes	Backup LBA (location of the other header copy)
+40	8 bytes	First usable LBA for partitions (primary partition table last LBA + 1)
+48	8 bytes	Last usable LBA (secondary partition table first LBA - 1)
+56	16 bytes	Disk GUID (also referred as UUID on UNIXes)
+72	8 bytes	Starting LBA of array of partition entries (always 2 in primary copy)
+80	4 bytes	Number of partition entries in array
+84	4 bytes	Size of a single partition entry (usually 128)
+88	4 bytes	CRC32 of partition array
+92	*	Reserved; must be zeroes for the rest of the block (420 bytes for a sector size of 512 bytes; but can be more with larger sector sizes)
LBA size	Total

  

GUID partition entry format
Offset	Length	Contents
0	16 bytes	Partition type GUID
16	16 bytes	Unique partition GUID
32	8 bytes	First LBA (little endian)
40	8 bytes	Last LBA (inclusive, usually odd)
48	8 bytes	Attribute flags (e.g. bit 60 denotes read-only)
56	72 bytes	Partition name (36 UTF-16LE code units)
128	Total

Partition attributes
Bit	Content
0	System partition (disk partitioning utilities must preserve the partition as is)
2	Legacy BIOS bootable (equivalent to active flag (typically bit 7 set) at offset +0h in partition entries of the MBR partition table)
60	Read-only
62	Hidden
63	Do not automount (i.e., do not assign drive letter)

From: http://en.wikipedia.org/wiki/GUID_Partition_Table