The FDL$PARSE routine parses an FDL specification, allocates
    OpenVMS RMS control blocks (FABs, RABs, or XABs), and fills in
    the relevant fields.

    Format

      FDL$PARSE  fdl_desc ,fdl_fab_pointer ,fdl_rab_pointer [,flags]

                 [,default_fdl_desc] [,stmnt_num]