>>656
試せばすぐ判るのに
https://ideone.com/nqxVHP

#include <stdio.h>

int main(int argc, char **argv)
{
long double f1 = 0.1;
long double f2 = 0.2;
long double f3 = 0.3;
long double f4 = f1 + f2;
printf("%.20Lf\n", f1);
printf("%.20Lf\n", f2);
printf("%.20Lf\n", f3);
printf("%.20Lf\n", f4);
printf("%d\n", f3 == f4);
return 0;
}