hex and dec 's default transfer

[Yanger_xy]

#include <iostream>
#include <iomanip>
using namespace std;

int main ()
{
int a = 21;
cout.unsetf (ios::dec);//if i delete this line ,the result is 21,
cout.setf (ios::hex);//why not it shows in hex, that is 15 ?
cout << a << endl;
return 0;
}

[Yanger_xy]

还是不明白！

[waizqfor]

ios::dec使用基数10输出
ios::hex使用基数16输出

[waizqfor]

ios::dec使用基数10输出
ios::hex使用基数16输出

[Yanger_xy]

i konw it,but i cann't understand that why the result is 21 if i delete this line :
" cout.unsetf (ios::dec); "
i think it shoud cout in hex, that is : 15

[Yanger_xy]

the "pinyin shu ru fa' on my computer has been overloaded ,but i do not konw how to setup it
so i have to use english even though my english is not very good !!

[taodm]

因为规矩是用cout << std::hex 、std::dec。
setf、unsetf是留给编译器自己用的，每个编译器下具体描述都不同。