Thread: custom include files

>>> Why do you need to make your own include files

You don't need to make your own include files at all. It is perfectly possible to create very large programs without. It is simply that most people, and almost all professionals do not choose to do it that way.

As your programmes get more complicated, (and larger), you will find you want to break your program up into several smaller files, not least for the fact that it compiles faster. If you change one line in a 100000 line program file, it will compile 100000 lines. If you've broken that up into 1000 line files, only one gets done. This is one reason for custom includes. Rather than re- prototyping and extern'ing your variables in each of your smaller files, your create an include with this stuff in it and #include it.

Once you get a bit more sophisticated, you'll want to start creating libraries and .DLL's. For the same reason, you'll create custom includes for each.

As with everything, there are other reasons as well, but think about these for now.

A very simple header file might look like this:
Call it: square.h

Code:

#ifndef GUARD_square_h
#define GUARD_square_h

//Function Prototype
int Square(int);

#endif

Its souce file might look this way:
Call it: square.cpp

Code:

#include "StdAfx.h"

int Square(int x)
{
   return x*x;
}

The simple implimentation program would look like this:
Call it: myprogram.cpp

Code:

#include "StdAfx.h"
#include "square.h"
#include<iostream>
using namespace std;

int main()
{
   cout << Square(10);
   return 0;
}

>>> Is this all correct...?

No. Dean's example is correct. The functions are prototyped in the header, and implemented in other .cpp files.

square.cpp doesn't need square.h.

actually no but in other cases when its expanded it may. habit forming ya know.