if u want to run the programm in backgrond by using the
standard program RSBDCSUB by executing .

loop at itab with control itab_tc.

Yes,You are right.If we write statement as :
Select-options : vbeln for vbrk-vbeln obligatory.
then low value gets mandatory.

We have to write as :
Select-options : vbeln for vbrk-vbeln.
Now vbeln field is not mandatory.
Now we have to explicitly write code for making high value 
mandatory in AT SELECTION-SCREEN event.

At selection-screen.
loop at vbeln where high is initial.
endloop.
IF SY-SUBRC ne 0.
 MESSAGE 'HIGH VALUE CAN NOT BE BLANK' TYPE 'E'.
ENDIF.

There is only one change required in the given code and 
that is IF SY-SUBRC eq 0.
Then the code will look like this

At selection-screen.
loop at vbeln where high is initial.
endloop.
IF SY-SUBRC EQ 0.
 MESSAGE 'HIGH VALUE CAN NOT BE BLANK' TYPE 'E'.
ENDIF.

SELECT-OPTIONS s_matnr for mara-matnr.

AT SELECTION-SCREEN.
  if s_matnr-high is INITIAL.
    message  'high cant be empty' TYPE 'E'.
  ENDIF.

use set parametr id for the mater number and then use call 
transaction 'MM01' statement your value that was captured 
will be passed to MM01 transaction.

this is for to open purchase order.
VAR contain PO no. BES is the parameter ID for PO no. field.

SET PARAMETER ID 'BES' FIELD VAR.
CALL TRANSACTION 'ME23N' AND SKIP FIRST SCREEN.

read table with key Numerics = '9'.
table-words = 'twenty'.
modify table.
clear table.

In case of Call transaction method, up to 74 all the 
records are processed and on 75 th row user has to correct 
error then only it will process further and finally updates 
the database.
In case of Session method all the non error rows will be 
processed by leaving 75th row. The error row will be shown 
in the error message list.

in CT method upto 74th record all the records will be updated to the database and we have to correct the the 75th row and then we can update it to database whereas in SM not a single record will be updated to database unless and until you clear the error.

You Can get smart form output in PDF format by writing a 
executable program with HTML Viewver.

Steps:
1. Create a Screen '100' for your program and create a 
Custom Control with name PDF.

2. Data diclaration for HTML Container:
data:g_html_container type ref to cl_gui_custom_container,
     g_html_control   type ref to cl_giu_htm_viewer,
     lv_url type char(255).

DATA : l_job_output_info TYPE ssfcrescl.
DATA : ls_control_param  TYPE ssfctrlop.


3. Fill ur data in internal table and call your smart form.
    Pass Values to Smartform
 CALL FUNCTION '/1BCDWB/SF00000166'
    EXPORTING
     control_parameters     = ls_control_param
     e_tpseg_start_date     = lv_e_tpseg_start_date
     e_tpseg_end_date       = lv_e_tpseg_end_date
   IMPORTING
     job_output_info        = l_job_output_info
   TABLES
     et_trip                = lt_trip
   EXCEPTIONS
     formatting_error       = 1
     internal_error         = 2
     send_error             = 3
     user_canceled          = 4
     OTHERS                 = 5.

You will Get data into OTF Format in "l_job_output_info".

3. You have to convert Data in PDF Format so, Call Function 
Module 'CONVERT_OTF' and pass "l_job_output_info-otfdata".

CALL FUNCTION 'CONVERT_OTF'
    EXPORTING
      format                = 'PDF'
    IMPORTING
      bin_filesize          = pdf_fsize
      bin_file              = p_c_ztr_reports-report_pdf
    TABLES
      otf                   = l_job_output_info-otfdata
      lines                 = lt_pdf
    EXCEPTIONS
      err_max_linewidth     = 1
      err_format            = 2
      err_conv_not_possible = 3
      OTHERS                = 4.

     
4 . You can use c_ztr_reports-report_pdf to load PDF Data 
into HTML Control by converting Xstring to binary table by 
function module 'SCMS_XSTRING_TO_BINARY'.

* Convert xstring to binary table to pass to the LOAD_DATA 
*method
  CALL FUNCTION 'SCMS_XSTRING_TO_BINARY'
    EXPORTING
      buffer     = p_c_ztr_reports-report_pdf
    TABLES
      binary_tab = lt_data.

You Will Get converted data into a internal table "lt_data".

5. Call Your Screen '100'.

 CALL SCREEN 100.

6. In PBO Module of 100 Screen.

7. Create object for HTML Container 
  Create Object g_html_container
     exporting 
      Container_name = 'PDF' " Name You have mentioned 
                               for Control Conatiner Screen.

8. Pass you defined html container to HTMl Control
    Create OBJECT g_htnl_contol
        exporting
          parent = g_html_container.

9. call intance method load data and pass your converted 
table into this method.
  * Load the HTML

  CALL METHOD g_html_control->load_data(
     EXPORTING
       type         = 'application'
       subtype      = 'pdf'
     IMPORTING
       assigned_url         = lv_url
     CHANGING
       data_table           =  lt_data
     EXCEPTIONS
       dp_invalid_parameter = 1
       dp_error_general     = 2
       cntl_error           = 3
       OTHERS               = 4 ).  
         
From this Method u will get URL in lv_url.

10. call method to show ur url at Your Screen.
 call method g_html_control->show_url( url = lv_url
                                        in_place ='X').


You Will Get your Smartform output in PDF at your screen..

Enjoy!!!!!!!!!!!!!!!

enhancement catagory used for applying restrictions 
on fields .i.e. if you you have selected enhancement cat. 
as  can be enhanced char type only ,
 then fields with char data type only you can
 create in table .

ece 4.7 password small ece 6.0 password big

E.C.C 6.0 is said to be the advanced version right now, 
inorder to reduce the more code and use more 
funcationalities, and for high performance testing we go 
with E.C.C 6.0..... It is said to support all type of 
functionalities in any conditions.

It also incorporates new technologies such as Enhancement 
framework and Switch Framework which were not supported in 
4.6/4.7.