The FDL$GENERATE routine produces an FDL specification and writes
    it to either an FDL file or a character string.

    Format

      FDL$GENERATE  flags ,fab_pointer ,rab_pointer [,fdl_file_dst]

                    [,fdl_file_resnam] [,fdl_str_dst] [,bad_blk_addr]

                    [,retlen]