The Reserve Event Flag routine allocates a local event flag
    number specified by event-flag-number.

    Format

      LIB$RESERVE_EF  event-flag-number

1  –  Returns

    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

2  –  Argument

 event-flag-number

    OpenVMS usage:ef_number
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference

    Event flag number to be allocated by LIB$RESERVE_EF. The event-
    flag-number argument contains the address of a signed longword
    integer that is this event flag number.