Variables in header files

My project consists of two source files and one header file.

DX.cpp

Code:

---

#include "stdafx.h"
//...
case WM_LBUTTONDOWN:
                    i+=0.1;
                    break;
//...

---

graphics.cpp

Code:

---

#include "stdafx.h"
//...
D3DXMatrixRotationX(&matRotateX, i);
//...

---

stdafx.h

Code:

---

//...
float i;
//...

---

The problem is that i need stdafx.h to be included in each of my source files, but that redefines i. Where should I put variables which I need in every souce file?

>Where should I put variables which I need in every souce file?
You can put the declarations for a variable in your header, but the definition should be placed in the implementation file:

Code:

---

//...
extern float i;
//...

---

Code:

---

#include "stdafx.h"
//...
float i;
//...
D3DXMatrixRotationX(&matRotateX, i);
//...

---

Of course, using a global name like i is flirting with disaster because it's such a common identifier. Also, stdafx.h is a well known header in Microsoft compilers, so it's unwise to reuse it.

> float i;
// put this in a header file
extern float i;

// put this in ONE source file
float i;

That is, if you insist on using global variables.

Meh - beaten by the alphabet again :(

I am wondering, what makes "stdafx.h" so popular header file name?

> what makes "stdafx.h" so popular header file name?
It's the name of the file which VC++ uses to implement "precompiled headers".

You put all the commonly used header files your project needs into stdafx.h
You then #include "stdafx.h" as the first include in all your source files.

Supposedly, it speeds up builds.
I do know one thing though, it is the single biggest PITA as almost every single noob has a question about it at some point.

Thanks guys, I can always rely on you. Now help me out with debugging :)