Query on WRITE_FORM ----TOP, BOTTOM areas

Question

What is the difference between the following 2 scenarios:: where there is a text element in SE71 Form with some text and in first scenario we are using the write form usi:ng export parameters TYPE and FUNCTION and in Second scenario we are we are using WRITE_FORM but without using Export parameters TYPE and FUNCTION, but using script contorl commands TOP and ENDTOP in the Form
1)Using a Text element 'TE'
CALL FUNCTION WRITE_FORM
    EXPORTING
         TEXT_ELEMENT   =  'TE'
          TYPE                  =  'TOP'
          FUNCTION           =  'SET'
2)In se71 form
/E  TE
/:   TOP
This is the sample text for Text element TE
/:    ENDTOP

Answer 1

A SAMPLE SUBROUTINE************************
DATA : A TYPE I VALUE 10.
PERFORM SUB.
*&      Form  SUB
      text
-->  p1        text
<--  p2        text
form SUB .
WRITE : A.
endform.                    " SUB
*************************A SUB-ROUTINE USING USING EXTENSION************
DATA : A TYPE I VALUE 10.
PERFORM SUB USING A.
WRITE : A.
*&      Form  SUB
      text
     -->P_A  text
form SUB  using    p_a.
P_A = P_A * 10.
WRITE : P_A.
endform.                    " SUB
ARUN REDDY I