联合体，和枚举

#include <iostream>

union data{
    int i;
    char c;
    float f;
};

enum weekday{sun,mon,tue,wed,thu,fri,sat};


int main()
{
    union data a; // 联合体，共用体所有成员共用一块空间
    a.i = 10; 
    a.c = 'a';
    a.f = 98.5;
    // 枚举
    enum weekday workday; // 枚举变量
    printf("%d\n",tue); // 枚举常量

    workday=mon;                                                                                            
    printf("%d\n",workday);
    return 0;
}