程序代码：

//求平均值（无限for循环）

#include <iostream>
using namespace std;

int main( )
{
    double value = 0.0;
    double sum = 0.0;
    int i = 0;
    char indicator = 'n';

    for( ; ;)                                   //无任何表达式，只有两个分号
    {
        cout << endl
            << "Enter a value: ";
        cin >> value;
        ++i;
        sum += value;

        cout << endl
            << "Do you want to enter anolther value ( enter y or n) ? ";
        cin >> indicator;
        if ((indicator != 'y') && (indicator != 'n'))
            cout << endl <<"Your enter is worng !" << endl;
        if((indicator == 'y') || (indicator == 'Y'))
            cout << endl << "ok!";
        if((indicator == 'n')|| (indicator == 'N'))
            break;
    }
    cout << endl
        << "The average of the " << i
        << " Values you entered is " << sum / i << endl;
   
    system("pause");
    return 0;
}