These vectors (0:0104 and 0:0118) are pointers to hard disk operating
parameter structures on AT-class and better computers.

See Hard Disk Parameter Table for a layout of the data at these vectors.

XT: Depending upon switch settings, one of four addresses are copied to
these vectors.

AT: At Boot time, the AT BIOS reads the CMOS Memory to learn which type(s)
of hard disk drives are attached.  It then points the vectors...

INT 41H  --> first hard disk
INT 46H  --> second hard disk

...to tables in ROM.  Many recent BIOSes are able to handle "user-defined"
hard-disk types.  They store the necessary parameters in non-volatile RAM
and copy them into memory at boot time.

See Also: BIOS Data Area
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INT 41H and INT 46H: Hard Disk Parameter Pointers