This is an easy one. It prints out what you want it to print out, and before you see what it says, the screen is cleared. Try this:
Code:
#include<iostream.h>
#include<conio.h> //change to conio.c if you're using Dev

int main (void)
{
    cout << "hello world";
    getch();  //pauses until you press somthing
    clrscr ();
    return 0;
}