When to use a void pointer?

Question

I understand the use of void pointer for malloc implementation.

void* malloc  ( size_t size );

Can anyone suggest other reasons or provide

Answer 1

It is commonly used in numerical code, for example a C root solver function might look like that:

double find_root(double x0, double (*f)(double, void*), void* params)
{
/* stuff */
y = f(x, params);
/* other stuff */
}

params is cast by f to some structure it knows about, but find_root doesn't.