Confusion with gmp_printf

[Bruce M. Axtens]

    mpf_t f;
    int n;
    gmp_printf ("fixed point mpf %.*Ff with %d digits\n", n, f, n);


In section 10.1 of the 4.2.4 manual, the above is given as an example of 
how to print an mpf number. What I don't understand is how that works 
given that 'n' is either zero or undefined (depending on C or compiler).

How do I get gmp_printf (or, in my case, gmp_sprintf) to output 
everything that's in an mpf_t without rounding.

Kind regards,
Bruce