double ++ てすと。

doublepp.c

#include<stdio.h>
int main()
{
        double n = 0.0;
        double x = 0.0;
        for (n = 0; n <= 30; n++) {
                x = 0.1 * n;
                printf("%.16e %.16g\n", x, n);
        }
        return 0;
}