Official Name: lFont_record
Memory Address: 845A
Length: 7 bytes.
These seven bytes contain a bitmap of the space of the cursor - it can be the cursor itself or whatever is under the cursor. Only the rightmost 6 bits are used, 1 byte per row.
Writing to this area does not seem to have any visible effect, so you might use this to store temporary variables. Remember that, if you do so, they will be destroyed as soon as the cursor does anything.