print more numbers for "cout"

Normally for double data, the precision is quite high. But when you want to show some data like "123456789.12345", it just show you "1.2356e+09". From that, we see it just show you the data with 5 precision. In fact, it does not lose any data. This is for easy to see. If you want to show more, you can do:

#include

double a=123456789.12345;
int n=14;
cout << setprecision(n) << a << endl;


This time it shows you "123456789.12345".