C++中 关于自定义数据类型

关于自定义数据类型
typedef 用于为已有的数据类型另外命名。一般这些命名是有意义的名字，从而提高了程序的可读性。类型申明的语句为 typedef 已有类型名 新类型名

#include <iostream>using namespace std;typedef double Area,Volume;typedef int Natural;int main(int argc, char *argv[]){    Natural i1=1,i2;    Area a;    Volume v;    cout<<"i1="<<i1;}

enum 为枚举类型，将该变量可取的值一一列举出来，便构成了一个枚举类型。需要注意的是1.枚举类型的取值只能是其枚举元素其中的一个。2.枚举元素按常量处理，不可以对其赋值，但可以在声明是另行定义枚举元素的值。3.枚举元素赋值给整形变量时不用强制类型转换，会自己调用隐含类型转换。但在整形变量赋值给枚举变量时，需要显示类型转换如：
A=week(fri);

#include <iostream>using namespace std;typedef double Area,Volume;typedef int Natural;enum weekday {    sun=7,mon=1,tue,wed,thu,fri,sat};int main(int argc, char *argv[]){    weekday week1;   enum  weekday week2=mon;   enum  weekday week3=weekday(1);   for(int count=mon; count<=sun;count++)   {       week1=weekday(count);       switch (week1)         {        case 1:cout<<"today is monday"<<endl;break;         case 2:cout<<"today is tuesday"<<endl;break;                case 3:cout<<"today is wednesday"<<endl;break;                case 4:cout<<"today is thusday"<<endl;break;                case 5:cout<<"today is friday"<<endl;break;                case 6:cout<<"today is satarday"<<endl;break;                case 7:cout<<"today is sunday"<<endl;break;   }   }   return 0;}

输出结果:

today is monday
today is tuesday
today is wednesday
today is thusday
today is friday
today is satarday
today is sunday