Simple Question About Extern

Hi, I'm trying to use extern for the first time, and it's not working. Here's the code:

test1.cpp:
------------------------------------
#include "test2.cpp"

int main(void)
{
hi();

return 0;
}
------------------------------------



and test2.cpp
------------------------------------
#include<iostream.h>

extern void hi(void)
{
cout << "hi" << endl;
}
------------------------------------

Thanks!

I have never seen extern used with functions. Usually, if you have a function declared in another file, you just use a prototype and thats the end of it. extern is usually when you have a variable declared in another file, but you want to use it somewhere else. For example:

test.cpp

void hello(void); // prototype

int my_extern_int = 0;

int main()
{
my_extern_int++;

hello();

return 0;
}

// test2.cpp

extern int my_extern_int; // now we can use it in this file too

void hello(void)
{
my_extern_int--;
}