#define NZEROS 4
#define NPOLES 4
#define GAIN   1.009351158e+00

static float xv[NZEROS+1], yv[NPOLES+1];

static void filterloop()
  { for (;;)
      { xv[0] = xv[1]; xv[1] = xv[2]; xv[2] = xv[3]; xv[3] = xv[4];
        xv[4] = next input value / GAIN;
        yv[0] = yv[1]; yv[1] = yv[2]; yv[2] = yv[3]; yv[3] = yv[4];
        yv[4] =   (xv[0] + xv[4]) + 4 * (xv[1] + xv[3]) + 6 * xv[2]
                     + ( -0.9815567827 * yv[0]) + ( -3.9444991525 * yv[1])
                     + ( -5.9443270236 * yv[2]) + ( -3.9813846512 * yv[3]);
        next output value = yv[4];
      }
  }