The Await Event Occurrence routine blocks the caller until an
    event occurs.

    Format

      PPL$AWAIT_EVENT  event-id [,output]

1  –  Arguments

 event-id

    OpenVMS usage identifier
    type          longword (unsigned)
    access        read only
    mechanism     by reference
    Identifier of the event. The event-id argument is the address of
    an unsigned longword containing the identifier.

    The event-id is returned by PPL$CREATE_EVENT.

 output

    OpenVMS usage user_arg
    type          longword (unsigned)
    access        write only
    mechanism     by reference
    Receives the event-param argument from PPL$TRIGGER_EVENT. The
    output argument is the address of an unsigned longword that
    receives the value of event-param. The value of event-param is
    copied to output when an event is triggered.