begin;
  dcl c  char       (1);
  dcl sx char       (1) based(px);
  dcl sy char       (1) based(py);
  dcl i  fixed bin (31);
  dcl px ptr            init (addr(C1));
  dcl py ptr            init (addr(C2));
  do i = 1 to min(stg(C1), stg(C2));
    c  = sx;
    sx = sy;
    sy = c;
    px = px + 1;
    py = py + 1;
  end;
end;