struct startup_info_disk

Contains the following:

struct startup_info_disk {
    struct startup_info_hdr     hdr;
    unsigned char               drive;
    unsigned char               zero;
    unsigned short              heads;
    unsigned short              cylinders;
    unsigned short              sectors;
    unsigned long               blocks;
};

Contains information about any hard disks detected (on a PC with a BIOS). The members are as follows:

drive

Drive number.

zero

Reserved; must be zero.

heads

Number of heads present.

cylinders

Number of cylinders present.

sectors

Number of sectors present.

blocks

Total blocksize of device. Computed by the formula heads × cylinders × sectors. Note that this assumes 512 bytes per block.