Partition / partition sector / boot sector
Partition:
A partition is a set of adjoined sectors on a hard disk.
Any sector of the hard disk belongs either to no partition or it belongs to
a specific partition, but it must not belong to more than one partition at the same time.
In other words, partitions must not overlap each other.
Typically, different
operating systems are installed on separate partitions. An operating system
can access all sectors of its partition, while access to sectors of other
primary partitions is not possible in many cases. On the other hand, sectors
of supported logical drives can be accessed without any problems.
There is the convention that partitions should always start and end on
cylinder boundaries. No rule is without exception: since the first sector of
a hard disk (C/H/S=0/0/1) is always reserved for the MBR and one does not want
to leave the complete zeroth cylinder empty, the first partition does not begin
on the next cylinder boundary (C/H/S=1/0/1) but directly after the track 0
at C/H/S=0/1/1. Hence only the sectors of the track 0 are left empty (with
the exception of the first sector). There is no compelling technical reason
for this convention. Linux and Windows NT/2000/XP/2003 seem to have no problems when partitions
do not start or end on cylinder boundaries. However other operating systems
(e.g. DOS) expect that this convention is obeyed.
Partition sector:
Every partition requires an accompanying partition sector. The partition sector
describes this partition, i.e. it contains the information about begin and end
of the partition and the type of the partition. All partition sectors have the
same structure, see format of partition sector.
The MBR is the common partition sector for primary and extended partitions.
On the contrary, to every logical drive belongs a separate
partition sector, which describes on one hand the logical partition and
on the other hand contains the position of the partition sector for the next
logical drive.
Boot sector:
The boot sector is the sector at the beginning of a bootable operating system partition.
The boot sector contains a small program. When this program is loaded and executed the
corresponding operating system is booted. The contents and the format of the boot
sector depends on the operating system. A certain boot sector can therefore
be used only for booting a particular operating system but not for booting any other
operating systems.
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