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