C++ 联合，枚举，类型

联合

Union类型和结构有很多相似之处

联合Union存放一个，就要顶替之前那个

#include <iostream>
using namespace std;

union AAA
{
unsigned long birthday;
unsigned short ssn;
char* pet;
};

int main()
{
AAA AAA_1;
AAA_1.birthday = 19911120;
cout << AAA_1.birthday << "\n";

AAA_1.pet = "Lucky";
cout << AAA_1.pet << "\n";
cout << AAA_1.birthday << "\n";
//实际上这里输出了一个上面Lucky字符串的地址

system("pause");
return 0;
}

枚举

枚举的值不是一个字符串，所以不需要引号。枚举生成的是按照顺序转化的从0开始的数字顺序

nt main()
{
enum weekdays { Monday, Tuesday, Wednesday, Friday };

weekdays today;

today = Monday;
cout << today << "\n";

today = Friday;
cout << today << "\n";
system("pause");
}

类型

如果不喜欢用int*来创建指针，可以像下面一样定义一个类型的别名

typedef int* intPtr；

之后就可以用intPtr 来定义整形指针