Thread: More digits in output, particular digits output, output in *.txt

I've started programming 1 week ago and I use win32 console for an output.

In program which calculates pi:
Code:

Code:

#include <iostream>
#include <math.h>
using namespace std;

int main()
{
  double b=-1;
  double pi=acos(b);
  cout << pi << endl;
  
  system("PAUSE");	
  return 0;
}

The output is:
Output:

Code:

3.14159

I know that computer calculated pi with much higher precision, so how do I get, I don't know... 15 digits on the output screen?

One more related question. I'm trying to write a random number generator program, since I've noticed that the rand() function doesn't have the uniform distribution of random number values, and for that I need a function that would "cut" double variable started from some decimal value to some other decimal value. For example, if I have a double variable number pi=3.141592654... I want a new integer variable with value from 3rd to 6th digit, int a=592. How do I do that?

The final question. If I want to test relationship between many output variables it would be very usefull if program could put these values in a txt file. How do I do that? Remember (I don't know if that maters) I'm programming (or trying to ), that is, the output is in win32 console.

Thank you!