Statement                     Description
AT FIRST ... END AT           The statement in this block will be executed 
                              if that record is a first record of internal table.
AT LAST ... END AT            The statement in this block will be executed
                              if that record is a last record of internal table.

AT NEW  ... END AT     The statement is this block will be executed
                              if the record contains value of the beginning group. 
AT END OF  ... END AT  The statement is this block will be executed
                              if the record contains value of the ending group.