程序代码：

第一种
#include < iostream >
#include < cstdlib >
using namespace std;

int main ( )
{
    const int N = 100;
    double sum = 0.0;
    int x = 1;
    do sum += 1.0 / x++;
    while ( x <= N );
    cout << " The sum of the first" << N << " reciprocals is " << sum;

第二种：
//迭代意指反复执行一条或多条语句，直至某个条件为真、
#include < iostream >
#include < cstdlib >
using namespace std;

int main ( )
{
    const int N = 100;
    double sum = 0.0;
    int x = 1;

repeat: sum += 1.0 / x++;
    if ( x < N )
        goto repeat;
    cout << "The sum of the first " << N << " reciprocals is " << sum;

    system ( "pause" );

}

第三种：
#include < iostream >
#include < cstdlib >
using namespace std;

int main ( )
{
    const int N = 100;
    double sum = 0.0;
    int x = 1;

    while ( x <= N )
        sum += 1.0 / x++;
    cout << "The sum of the first " << N << " reciprocals is " << sum;

    system ( "pause" );

    return 0;
}


第四种：
#include < iostream >
#include < cstdlib >
using namespace std;

int main ( )
{
    const int N = 100;
    double sum = 0.0;

    for ( int x = 1; x <=N; x++ )
        sum += 1.0 / x;
    cout << "The sum of the first " << N << " reciprocal is " << sum << endl;

    system ( "pause" );

    return 0;
}



再发个漂亮的图案玩玩：


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

int main ( )
{
    const int N = 10;
    for ( int i = 0; i < N; i++ )
    {
        for ( int j = 0; j < 2 * N; j++ )
        if ( j < N -i || j > N + i ) cout << " ";

        else cout << "*";
        cout <<"\n";
    }
   
    system ( "pause" );

    return 0;
}



    system ( "pause" );

    return 0;
}