An indicator of the format/operating system on this partition.
Some common values of interest include (symbolic names are defined in lvm_data.h):
0x00 UNUSED_INDICATOR 0x01 FAT12_INDICATOR 0x04 FAT16_SMALL_PARTITION_INDICATOR 0x05 EBR_INDICATOR or EBR_FORMAT_INDICATOR 0x06 FAT16_LARGE_PARTITION_INDICATOR 0x07 IFS_INDICATOR 0x0A BOOT_MANAGER_INDICATOR 0x0E FAT16X_LARGE_PARTITION_INDICATOR 0x0F WINDOZE_EBR_INDICATOR or EBR_FORMAT_INDICATORX 0x10 BOOT_MANAGER_HIDDEN_PARTITION_FLAG 0x35 LVM_PARTITION_INDICATOR
See the description of the OS_Flag field under Partition_Information_Record for various other possible values.
Note: When creating a new partition, the LVM Engine will set the value of Format_Indicator to either 0x16 (for inactive or 'hidden' primary partitions), or 0x06 (for all other primary or logical partitions).