Used in conjunction with the contents of 32727. Holds the identifier of the blackboard ERIC wrote on (see 24133), or the descent table entry pointer (160-180; see 64460), or the MSB of the address of a routine (or an entry point to a routine) for dealing either with ERIC or with the result of an action by ERIC (see 57669, and 32727 for a list of the routine and entry point addresses).