作用：用于根据表达式的值返回真值或假值

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<string>
using namespace std;
int main()
{
	//逻辑运算符	非！
	int a = 10;
	int b = 20;
	//在c++中除了0都是真
	cout << !a << endl;		//0

	cout << !!a << endl;	//1

	//逻辑运算符	与&&
	a = 10;
	b = 10;
	cout << (a&&b) << endl;		//1

	a = 0;
	b = 10;
	cout << (a && b) << endl;		//0

	a = 0;
	b = 0;
	cout << (a && b) << endl;		//0

	//逻辑运算符	或||	
	a = 0;
	b = 10;
	cout << (a && b) << endl;	//1

	system("pause");

	return 0;
}

运行结果：

0
1
1
0
0
1
1
0

注：

与：同真为真，其余均为假

或：同假为假，其余均为真