What exactly do zippers and backfills mean in the compilation principle?

Backfilling technology means that when Boolean expressions in control statements are translated into quaternary sequences, some transfer addresses are unknown while generating these quaternary sequences, so it is necessary to backfill this address at an appropriate time. Zipper technology refers to in order to record the quaternary address that needs to be backfilled, e? The quaternion of Ture is drawn as a chain, which is called "true chain"; Basu ...