The B-tree index project can be maintained on a disk rather than in dynamic memory. The first record on the index file should contain metadata about the index, including the location of the root entry in the file and the address of the compare function for the data. Modify the B-tree ADT to maintain the B-tree on a disk. In this version of the ADT, the create B-tree function is replaced by an open file function. The compare function must be defined when the file is opened.