const Pointer

Consider

      const float pi = 3.1415;
      float pdq = 1.2345;
      const float *p = π
      float* const d = π    /* WRONG */
      float* const q = &pdq;
      const float *const r = π

      *p = 3.0;    /* WRONG */
      p = &pdq;    /* OK */
      *p = 3.0;    /* still WRONG */

      *q = 3.0;    /* OK */
      q = &pdq;    /* WRONG */

      *r = 3.0;    /* WRONG */
      r = &pdq;    /* WRONG again */

• const qualifier can refer to what is pointed at (frequent usage)

• const qualifier can refer to pointer itself (rare usage)

• const qualifier can refer to both (infrequent usage)