Flow control: loop (while)

data: NUM type I,
      STR(1).

while SY-INDEX < 10.
  STR = SY-INDEX.
  NUM = NUM + SY-INDEX.
  if SY-INDEX > 1.
    write '+'.
  endif.
  write STR.
endwhile.

write: '=', NUM.

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 =          45