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 
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