当我执行此操作时，每次输入7时，PC都会发出“嘟嘟”声。有人能解释一下为什么吗？我使用此标题：http://www.stroustrup.com/Programming/std_lib_facilities.h
int main()
{
double d = 0;
while (cin >> d){
int i = d;
char c = i;
int i2 = c;
cout << "d==" << d
<< " i==" << i
<< " i2==" << i2
<< " char==(" << c << ")\n";
}
}