Monday, October 31, 2011

What is disk partition table?

Disk partition table (DPT) is used to record the information of small amount of space in the disk partitions. It is located at track 0, cylinder 0, and sector 1 on the hard disk.

The 1 sector, 0 cylinder, 0 track (0 sector) on the hard disk is the hidden sector (all sectors on 0 track, 0 cylinder are hidden sectors. Common command would lead no access to these hidden sectors. The other 62 sectors on this track are also hidden. Multiple boot programs would locate all program code on other hidden sectors; some boot virus also put its code in other hidden sectors). Of all 512 byte of this sector, main boot record, MBR, will take up 446 byte (offset address 00H to 1BDH) another 64 byte ( offset address 1BEH to 1FDH) is the DPT and the last 2 byte 55AA is the symbol of the end of the partition.

DPT starts from 1BEH byte takes up 64 byte including four partition table items. Each partition table item would take up 16 byte. It always contains boot symbol, system symbol, cylinder number for start and end, sector number, head number, number of sectors before the partition, and numbers of sectors this partition takes up. Of which, the boot symbol shows whether the partition can be booted and whether the partition is active partition. When the boot symbol is 80, this partition is active partition. System symbol will show the type of partitions. Such as 06 stands for partitions with FAT 16 format, 0B stands for FAT 32 Partitions, 07 stands for NTFS partition, and 63 stands for UNIX partitions. The cylinder number marks end and start, sector number, head number defines the starting point and ending point of the partitions.

Partition Wizard is a partition manager that works perfectly well with MBR. It allows you to rebuild MBR and makes your disk management easy.

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