C语言--输出a的二进制（补码）中1的个数

1、写一个函数输出a的二进制（补码）中1的个数。

int count_(int a)
{
	int count = 0;
	for (int i = 0; i < 32; i++)
	{
		if (((a >> i) & 1) == 1)
			count++;
	}
	return count;
}
int main()
{
	int count = 0;
	int a = 0;
	scanf("%d", &a);
	count=count_(a);
	printf("count = %d\n", count);
}