q about bindings to C (noob)

[RomanZ via Digitalmars-d-learn]

version(RefOut)
        extern(C) void fun(out int input, ref in output);
else
        extern(C) void fun( /*[out]*/ int* input, const(float)* output);
        
version = RefOut;
void main() {
        int input;
        float output;
	fun( input, output ); // work fine; is it correct binding? or 
where the trouble?
}