(BIBOP) Where data objects are tagged with some kind of descriptor (giving their size or type for example) memory can be saved by storing objects with the same descriptor in one "page" of memory. The most significant bits of an object's address are used as the BIBOP page number. This is looked up in a BIBOP table to find the descriptor for all objects in that page.
[David R. Hanson. "A portable storage management system for the Icon programming language". Software - Practise and Experience, 10:489-500 1980].