Managed C++/CLI

extern int var1=0;
thread1
{
var1=10;
}
thread2
{
read var1;
}

// SieveOfErathostenes.cpp : main project file.

#include "stdafx.h"
#include <bitset>
#include <iostream>
#include <ctime>

using namespace System;

int main(array<System::String ^> ^args)
{
    const int N = 2000000;
    clock_t cstart = clock();

    bitset<N + 1> b;
    int count = 0;
    int i;
    for (i = 2; i <= N; i++)
        b.set(i);
    i = 2;

    while (i * i <= N)
    {
        if (b.test(i))
        {
            count++;
            int k = 2 * i;
            while (k <= N)
            {
                b.reset(k);
                k += i;
            }
        }
        i++;
    }

    while (i <= N)
    {
        if (b.test(i))  count++;
        i++;
    }

    clock_t cend = clock();
    double millis = 1000.0 * (cend - cstart) / CLOCKS_PER_SEC;

    cout << count << " primes \n" << millis << " milliseconds\n";

    return 0;
}