HP Vectra Technical Reference Manual page 334

A partition entry consists of 16 bytes. It contains information specifying the location of the
partition, type of operating system, and a flag to indicate if the partition is active. Table 10.5
details the partition table entry.
Table 10.5
Partition Table Entry Record
Size
1 Byte
1 Byte
1 Byte
1 Byte
1 Byte
1 Byte
1 Byte
1 Byte
2 Words
2 Words
Description
Boot indicator.
Starting head number.
Starting sector number.
Starting cylinder number.
*
System indicator.
* *
Ending head number.
Ending sector number.
Ending cylinder number.
*
Number of sectors in preceding partitions.
Total number of sectors in partition.
*
The actual cylinder number is a ten bit value composed of the cylinder byte plus the two
most significant bits of the associated sector byte. These two bits are the most significant bits
of the ten bit number.
* *
System indicators are:
DOH
=
Unknown operating system
01 H
=
DOS (12 bit FAT)
04H
=
DOS (16 bit FAD
The INT 19H code will load the code module contained in the master boot record into memory,
then transfer control to it. This code scans the data in the disc partition table to determine the
active partition, and its starting cylinder. The first sector of the active partition becomes the
logical boot sector of the partition, and it contains a boot record. The boot record has the same
format as the boot record contained on a flexible disc, except that some of the parameters are
adjusted for the increased capacity of the hard disc partition. Refer to table 10.3 for the format
of a typical boot record.
System Processes 325