Question

Consider the below code:

#include <iostream>
using namespace std;

int main ()
{
  int a;
  double b;
  cout << "Enter a number to be divided by three" << endl;
  cin >> a;
  b = a / 3.0;
  cout << "The result of this is:" << b << endl;
  return 0;
}

How can I set how many variables I would like to store after the decimal point? This includes above 20 digits.

Answer 1

double is a fixed-size type (8 bytes on most systems). So it only stores numbers to a certain precision. There’s no need to fear “infinite division” (in the sense that 1/3.0 has no finite decimal representation).

Edit (based on comments below)

If you are actually looking for an arbitrary-precision real number representation, you have to use a library for that, such as Boost.Multiprecision.