One of my "non-programmer" friends recently decided to make a C++ program to solve a complicated mechanical problem.

He wrote each function in a separate .cpp file, then included them all in the main source file, something like this:

main.cpp:

#include "function1.cpp"
#include "function2.cpp"
...
int main() 
{
...

}

He then compiled the code, with a single gcc line:

g++ main.cpp    // took about 2 seconds

Now, I know that this should work, but I'm not sure whether including .cpp files directly into the main program is a good idea. I have seen the following scheme several times, where all the function prototypes go into a header file with the extern keyword, like this:

funcs.h:

extern void function1(..);
extern void function2(..);
...

main.cpp:

...
#include "funcs.h"
...

& compiling with:

g++ -c function1.cpp
g++ -c function2.cpp
...
g++ -c main.cpp
g++ -o final main.o function1.o function2.o ...

I think that this scheme is better (with a makefile, ofcourse). What reasons can I give my friend to convince him so?

c++ g++ compilation
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