Used in conjunction with the contents of 7FD7. Holds the identifier of the blackboard ERIC wrote on (see 5E45), or the descent table entry pointer (0xA0-0xB4; see FBCC), 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 E145, and 7FD7 for a list of the routine and entry point addresses).