Hi mariya,
Within ABAP Objects, you can only use internal tables without a header line. You can always address the body of an internal table <itab> explicitly by using the following syntax: <itab>[]. This syntax is always valid, whether the internal table has a header line or not.
Example :
DATA itab1 TYPE TABLE OF i WITH OUT HEADER LINE.
DATA itab2 TYPE TABLE OF i WITH HEADER LINE.
itab1 = itab2. " Only header lines will be copied
itab1 = itab2[]. " Copies table body
Regards Ashwin