并行计算――混乱的输出?

I'm trying to learn the basics of parallel computing, but I'm running into an issue on my computer. Take a look at my code below. Basically, I want to print out the line "Hello World!" for every core my computer has. My computer has four cores, so it should print out that line four times. If I were to use the commented-out 'cout' line instead of the 'printf' line, the output would be all jumbled up. This is because the ' ' escape command is executed separately from the "Hello World!", so the new line output would occur randomly. The 'printf' line is a solution to this problem, because the line is executed all at once (not split up into parts like the 'cout' line). However, when I use 'printf', my output is still all jumbled up as if I used 'cout'. I have no idea why it does this. I tried the exact same code on another computer, and it works perfectly. It's only my computer that continues to jumble up the output with 'printf'. I've emailed my CS professor about it, and he has no idea why it's doing this on my computer. I know I set up OpenMP on my computer correctly. Does anyone with parallel computing experience know why this is messing up on my computer?

#include <omp.h>
#include <stdio.h>
#include <iostream>
#include <stdlib.h>
using namespace std;

int main()
{
    #pragma omp parallel
    {
        printf("Hello World!
");
        //cout << "Hello World!
" << endl;
    }
    return 0;
}

为了说明我在说什么，这是我在计算机上运行上述代码时的输出: