#include <stdio.h>
#include <stdlib.h>
#include <math.h>

/*This program will generate a list of prime numbers up to UPPERLIMIT*/
int IsPrime(int);

#define UPPERLIMIT 2000000

FILE *file;
char *filename = "C:\\Users\\chris\\Documents\\primelist.txt";

int main()
{
    int x;
    unsigned long long total = 2;

    printf("Opening file %s\n", filename);

    file = fopen(filename,"a");

    if (file == NULL)
    {
        printf("File could not be open\n");
        return 0;
    }

    printf("Generating list of primes to %s\n", filename);
    /*fprintf(file, "---Starting Generation---\n");*/
    printf("2\n");
    fprintf(file, "%i\n", 2);
    for (x = 3; x <= UPPERLIMIT; x+=2)
    {
        if (IsPrime(x))
        {
            printf("%i\n", x);
            total = total + x;
            fprintf(file, "%i\n", x);
        }
    }

    printf("%llu\n", total);
    fclose(file);
    return 0;
}

int IsPrime(int x)
{
    int index;

    if (x % 2 == 0) {return 0;}

    for (index = 3; index < x; index++)
        {
            if ((x % index) == 0)
            {
                return 0;
            }
        }
    return 1;
}