If you need to download the internal table into an Excel document in ABAP program, you can use the class cl_salv_export_tool_xls to achieve it. Please check below for the sample code.

report z_gary_test1.

data: gt_t000 like table of t000.
data: gt_fieldcat type lvc_t_fcat,
      gs_fieldcat type lvc_s_fcat.
data: gv_length   type i.
data: gt_stream   type salv_xml_xline_tabtype.
data: gv_filename type string.

data: gr_data      type ref to   data,
      go_tool_xls  type ref to   cl_salv_export_tool_xls,
      go_config    type ref to   if_salv_export_configuration,
      gv_content   type          cl_salv_export_tool=>y_file_content,
      go_exception type ref to   cx_salv_export_error.

start-of-selection.
  select *
    into table gt_t000
    from t000.

* Create an instance of the export tool for table a given table gt_t000
  get reference of gt_t000 into gr_data.
  go_tool_xls = cl_salv_export_tool=>create_for_excel( gr_data ).

* Configure export properties
  go_config = go_tool_xls->configuration( ).

* Get fieldcat by ABAP structure
  call function 'LVC_FIELDCATALOG_MERGE'
    exporting
      i_structure_name       = 'T000'
      i_bypassing_buffer     = 'X'
    changing
      ct_fieldcat            = gt_fieldcat[]
    exceptions
      inconsistent_interface = 1
      program_error          = 2
      others                 = 3.
  if sy-subrc <> 0.
    clear gt_fieldcat[].
    exit.
  endif.

  "Complete fieldcatalog
  call function 'LVC_FIELDCAT_COMPLETE'
    changing
      ct_fieldcat = gt_fieldcat[].

  loop at gt_fieldcat into gs_fieldcat.
    go_config->add_column( header_text  = |{ gs_fieldcat-coltext }|
                           field_name   = |{ gs_fieldcat-fieldname }|
                           display_type  = if_salv_export_column_conf=>display_types-text_view ).
  endloop.

* Create the excel document
  try.
      go_tool_xls->read_result(
        importing content = gv_content ).
    catch cx_salv_export_error into go_exception.
      message id go_exception->if_t100_message~t100key-msgid
              type 'E'
              number go_exception->if_t100_message~t100key-msgno .
  endtry.

* Set Filename
  gv_filename = 'H:\Downloads\t000.xlsx'.

* Convert to Binary
  call function 'SCMS_XSTRING_TO_BINARY'
    exporting
      buffer        = gv_content
    importing
      output_length = gv_length
    tables
      binary_tab    = gt_stream.

* Download
  cl_gui_frontend_services=>gui_download(
    exporting
      bin_filesize = gv_length
      filetype     = 'BIN'
      filename     = gv_filename
    changing
      data_tab     = gt_stream
    exceptions
      file_write_error        = 1
      no_batch                = 2
      gui_refuse_filetransfer = 3
      invalid_type            = 4
      no_authority            = 5
      unknown_error           = 6
      header_not_allowed      = 7
      separator_not_allowed   = 8
      filesize_not_allowed    = 9
      header_too_long         = 10
      dp_error_create         = 11
      dp_error_send           = 12
      dp_error_write          = 13
      unknown_dp_error        = 14
      access_denied           = 15
      dp_out_of_memory        = 16
      disk_full               = 17
      dp_timeout              = 18
      file_not_found          = 19
      dataprovider_exception  = 20
      control_flush_error     = 21
      not_supported_by_gui    = 22
      error_no_gui            = 23
      others                  = 24 ).
  if sy-subrc <> 0.
    message e000(zdev) with 'Fail to download the file' space space space.
  else.
    message s000(zdev)  with 'Download the file successfully' space space space.
  endif.