When you want to download internal table to PC file in ABAP/4, you can apply function module "WS_DOWNLOAD".

Example

  CALL FUNCTION ’WS_DOWNLOAD’
       EXPORTING
            FILENAME                = LV_TEXT   "PC File Name and Location
            FILETYPE                = ’DAT’
       TABLES
            DATA_TAB                = I_MESG    "Internal Table
       EXCEPTIONS
            FILE_OPEN_ERROR         = 1
            FILE_WRITE_ERROR        = 2
            INVALID_FILESIZE        = 3
            INVALID_TYPE            = 4
            NO_BATCH                = 5
            UNKNOWN_ERROR           = 6
            INVALID_TABLE_WIDTH     = 7
            GUI_REFUSE_FILETRANSFER = 8
            CUSTOMER_ERROR          = 9
            OTHERS                  = 10.