# More digits in output, particular digits output, output in *.txt

• 11-30-2005
Ene Dene
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!
• 11-30-2005
dimirpaw
Do you mean PI as in PIE? Well so far it's been 100% impossible to get the exact digits for pie since the Math Professers and other researchers are still getting 3.################################### ect...

Now I'm new as well but I might be able to just give my thought. The number PI= what your trying to get may be more bytes then a double can hold. Well thats just my guess.
• 11-30-2005
Ene Dene
Quote:

Originally Posted by dimirpaw
Do you mean PI as in PIE? Well so far it's been 100% impossible to get the exact digits for pie since the Math Professers and other researchers are still getting 3.################################### ect...

Now I'm new as well but I might be able to just give my thought. The number PI= what your trying to get may be more bytes then a double can hold. Well thats just my guess.

Of course that I didn't mean PI with infinite number of digits (as I stated by "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?"), it is transcedental, by definition it is imposible, but that was not the question.
• 11-30-2005
Enahs
Code:

```#include <cmath> #include <iomanip> .... ....         cout << setprecision (15) << pi; //or any # .....```
• 11-30-2005
Ene Dene
Thanks!