proc iml;                            /* begin IML session */

      start approx(x);                          /* begin module */
         y=1;                                   /* initialize y */
         do until(w<1e-3);                     /* begin do loop */
            z=y;                                     /* set z=y */
            y=.5#(z+x/z);               /* estimate square root */
            w=abs(y-z);           /* compute change in estimate */
         end;                                    /* end do loop */
         return(y);                     /* return approximation */
      finish approx;                              /* end module */

      t=approx({3,5,7,9});             /* call function APPROX  */
      print t;                                  /* print matrix */

     
  quit;