Hi. I'm completely new to C++ (and to this site) and I am having trouble with the following code:
Code:
#include <iostream>
#include <fstream>
using namespace std;

long cnum=1;
const unsigned long fin = 100000;
const unsigned long group = 100;
unsigned long cursec=0;


ofstream destination("results.txt");



bool checkPrime (unsigned long num)
{
      for (int i=2;i<num;++i)
      {
            if ((num % i) == 0)
                   return false;
      }
            return true;
}


class sector
{
      public:
      sector ()
             {
                   destination << (cursec*group)+1 << " - " << (cursec+1)*group << " ";
                   ++cursec;
             }

      ~sector ()
              {
                    destination << "/n";
              }
};

void fill ()
{
     int primes=0;
     int a;
     a = (int) group;
     bool sector[a];
     for (int i=0;cnum<=(cursec*(group+1));++i)
     {
         if (checkPrime(cnum))
         {
                 ++primes;        
                 sector[i]=true;
         }
     }
     destination << primes;
}
         
         

int main ()
{
    for (;cnum<=fin;)
    {
       sector asect;
       fill();
    }
}
What I want the program to do is write a file that shows how many prime numbers are in a given size of numbers (100) over a large amount of numbers (100000).
I can compile the program but when I run it it crashes.
There is no real purpose to tis program other than being a learning exercise and helping me understand why this doesn't work would be much appreciated (along with tips on my coding style).