如何得到系统table和自定义type的信息

How to get info of system table or the type we defined in program?
Please refer follwing codes i wrote, we can leverage two FM.

REPORT  zdavid_component                        .

TYPES: BEGIN OF t_typ,
         line TYPE char100,
       END OF t_typ.
DATA: wa_typ TYPE t_typ,
      it_typ TYPE TABLE OF t_typ,
      it_data TYPE TABLE OF t_typ.

wa_typ-line = '1111'.
APPEND wa_typ TO it_typ.

DATA: tbl_name TYPE x030l-tabname,
      it_flds  TYPE TABLE OF rfc_fields.
tbl_name = 'MARA'.

CALL FUNCTION 'DP_GET_FIELDS_FROM_TABLE'
  EXPORTING
    tabname          = tbl_name
  TABLES
    data             = it_data
    fields           = it_flds
  EXCEPTIONS
    dp_invalid_table = 1
    OTHERS           = 2.
IF sy-subrc <> 0.
* MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
*         WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
ENDIF.

DATA: it_components TYPE TABLE OF rstrucinfo.
CALL FUNCTION 'GET_COMPONENT_LIST'
  EXPORTING
    program    = sy-repid
    fieldname  = 'wa_typ'
  TABLES
    components = it_components.

WRITE 'End'.