#include <iostream.h>

void main()
{
int a;
cout <<"please input a number:\n";
cin >>a;

int c1 = a%3 ==0;
int c2 = a%5 ==0;
int c3 = a%7 ==0;

switch((c1<<2)+(c2<<1)+c3){
case 0: cout <<"不能被3,5,7整除.\n"; break;
case 1: cout <<"只能被7整除.\n"; break;
case 2: cout <<"只能被5整除.\n"; break;
case 3: cout <<"可以被5,7整除.\n"; break;
case 4: cout <<"只能被3整除.\n"; break;
case 5: cout <<"可以被3,7整除.\n"; break;
case 6: cout <<"可以被3,5整除.\n"; break;
case 7: cout <<"可以被3,5,7整除.\n"; break;
}
}
在这个程序中switch内的公式不明白~!
"<<"的意思是什么?
请高手指点~!!!!!