список полей таблицы или структуры

1. Старый способ

DATA td TYPE sydes_desc.
DESCRIBE FIELD ct_to INTO td.

1 2	DATA td TYPE sydes_desc. DESCRIBE FIELD ct_to INTO td.

2. Новый способ

классы cl_abap_tabledescr и cl_abap_structdescr (для версии 4.6 и выше)

METHOD get_output_components . 
  DATA: 
    lcl_table_descr TYPE REF TO cl_abap_tabledescr, 
    lcl_struc_descr TYPE REF TO cl_abap_structdescr 
  . 
  FIELD-SYMBOLS: 
    <lt_output> TYPE STANDARD TABLE 
  . 
  ASSIGN me->output_tab->* TO <lt_output>. 
  lcl_table_descr ?= cl_abap_typedescr=>describe_by_data( <lt_output> ). 
  lcl_struc_descr ?= lcl_table_descr->get_table_line_type( ). 
  it_components = lcl_struc_descr->components. 
ENDMETHOD.

METHOD get_output_components .

DATA:

lcl_table_descr TYPE REF TO cl_abap_tabledescr,

lcl_struc_descr TYPE REF TO cl_abap_structdescr

FIELD-SYMBOLS:

<lt_output> TYPE STANDARD TABLE

ASSIGN me->output_tab->* TO <lt_output>.

lcl_table_descr ?= cl_abap_typedescr=>describe_by_data( <lt_output> ).

lcl_struc_descr ?= lcl_table_descr->get_table_line_type( ).

it_components = lcl_struc_descr->components.

ENDMETHOD.

или еще проще

DATA: lo_struct TYPE REF TO cl_abap_structdescr.
lo_struct ?= cl_abap_typedescr=>describe_by_name( structure_name ).
ASSIGN lo_struct->components TO FIELD-SYMBOL(<fields>).

DATA: lo_struct TYPE REF TO cl_abap_structdescr.

lo_struct ?= cl_abap_typedescr=>describe_by_name( structure_name ).

ASSIGN lo_struct->components TO FIELD-SYMBOL(<fields>).