VMS Help System Services, $SETEF  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Sets an event flag in a local or common event flag cluster.
    The condition value returned by $SETEF indicates whether the
    specified flag was previously set or clear. After the event flag
    is set, processes waiting for the event flag to be set resume
    execution.

    Format

      SYS$SETEF  efn

    C Prototype

      int sys$setef  (unsigned int efn);

1 - Argument

 efn

    OpenVMS usage:ef_number
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Number of the event flag to be set. The efn argument is a
    longword containing this number; however, $SETEF uses only the
    low-order byte.

    Two local event flag clusters are local to the process: cluster 0
    and cluster 1. Cluster 0 contains event flag numbers 0 to 31, and
    cluster 1 contains event flag numbers 32 to 63.

    There are two common event flag clusters: cluster 2 and cluster
    3. Cluster 2 contains event flag numbers 64 to 95, and cluster 3
    contains event flag numbers 96 to 127.