Prime Number Checker
Instead of hard-coding 1000000000, use a constant:

const int maxPrimes = 1000000000;


Then, use it in the loop like this:

for (int i = 3; i &lt; maxPrimes; i+=2)


This will make it clear what this value is.

Regarding the timing, you could use something from &lt;ctime&gt; or another suitable library to time certain code sections. For instance, you may time the loop in main() or just the one in primeChecker() for testing purposes.  This may be OS-dependent, so I'll let you decide on this if you wish to try it.