Interview Question for Software Engineer at Google:

Recursive:
void fib(int k)
{
    if(k==0)
        return 0;
    if(k==1)
        return 1;
    return fib(k-1)+fib(k-2);
}

Iterative:
void fib(int k)
{
    if(k==0)
        return 0;
    if(k==1)
        return 1;
    int pre2Term =0;
    int preTerm =1;
    int retVal = 0;
    for(int i=2 ; i<=k;i++)
    {
        retVal += preTerm + pre2Term;
        pre2Term = preTerm;
        preTerm = retVal;
}
return retVal;
}

Test:
fibTest()
{
    int testInt = 3;
    print(fib(testInt));
}

Iterative version of course has better performance because it doesn't need multiple function calls and program stacks to save variables.