C++Map称为联合容器，其中的元素是(惟一)关键字及其关联值的二元组，这些元素按照关键字有序。

例如，你可以创建一个字符串和整数的联合容器，然后在容器中插入各个月份及其天数的二元组：

 map<string, int> months;

 months.insert(make_pair("January", 31);
 months.insert(make_pair("February", 28);
 months.insert(make_pair("March", 31);
   ...
   
 months.insert(make_pair("December", 31);

 map<string,int>::iterator iter;
 for( iter = months.begin(); iter != months.end(); ++iter ) {
  cout << iter->first << " has " << iter->second << " days" << endl;
}
 

你可以想象，程序的输出是：

January has 31 days
February has 28 days
   ... 
December has 31 days.