Why the screen can only show 6 numbers even though I have used datatype "long double"?

Question

I am trying to input the first term, the second term and the terms number of a geometric sequence to find the geometric series.

#include <iostream>
using namespace std;

int main() {

double a,b,n,s,p,r;
cin >> a >>b>>n;
r= b/a;
p=1;
for(int i=0;i<n;i++) {
p=p*r;
};
s=(a-a*p)/(1-r);
cout<< s <<endl;

return 0;
}

Answer 1

I find that the printf function is a little nicer than cout for precision output. You could replace the cout statement with this:

printf("%lf\n", s);

There is a way to control precision in cout, but once you set it, you cannot reset cout's properties within the program back to the default automatic formatting.

#include <iomanip>
.
.
.
cout << setprecision(42) << s <<endl;

Answer 2

It helps. Thank you