Why does scanf() need "%lf" for doubles, when printf() is okay with just "%f"?

Question

Why is it that `scanf()` needs the `l` in "`%lf`" when reading a `double`, when `printf()` can use "`%f`" regardless of whether its argument is a `double` or a `float`?Example code: double d; scanf("%lf", &d); printf("%f", d);

Answer 1

On input, scanf matches %f with the address of the double, rather than float.

The type mismatch causes unpredictable results.

It will compile.

Output does not do this type checking.