C语言小白求助！！！！！！！！！！！！！！

{
int n_odd = 0;
int n_even = 0;
int sum_odd = 0;
int sum_even = 0;
int input = 0;

printf("Please enter integer to be analyzed(0 to terminate):");
while (scanf_s("%d", &input)) //这里的scanf函数是什么意思？为什么可以这样用？
{
if (0 == input)
{
break;
}
else if (0 == (input % 2))
{
n_even++;
sum_even += input;
}
else
{
n_odd++;
sum_odd += input;
}
}

printf("the average value of %d even is: %f; the average value of %d odd is: %f\n", n_even, (float)(sum_even/n_even), n_odd, (float)(sum_odd/n_odd));

return;

}