The exchange BASIC program switches item-IDs of the two specified items following the file reference.
exchange file.reference item-ID1 item-ID2
Swaps the item-IDs for program 1 and program 2. After exchanging the body of program 2, it is associated with the item-ID program 1 and vice-versa.
exchange bp program1 program2 Item 'program1' exchanged with 'program2' in file 'bp'