#ifndef

term. Essentially the entire header file is an IF statment. Because the term MATH_H has to be unique, we ask

#ifndef

if not defined then perform all of the statements after until the next

#endif

end of if statment.

#ifndef SOME_UNIQUE_NAME_HERE
#define SOME_UNIQUE_NAME_HERE   

// your declarations here   

#endif

SO, the “MATH_H” is merely some unique name to ensure the particular header file is not included more than once. I still don’t understand the

#ifndef</PRE part though.

I still don’t understand the first two lines in the add.h file.

#ifndef MATH_H

and

#define MATH_H

My first impression was “ifndef” was a typo of “define” with “MATH_H” being a derivative of “math.h”. Apparently I’m wrong since it does in fact work. I just don’t understand the where and how of those two lines substance.

#define

makes sense

#ifndef

I don’t understand. It looks like “define” scrambled.

MATH_H

I don’t understand. “math.h” would seem to make more sense. I surmise “MATH_H” is a Microsoft addon to the standard library though I would think that would require an include statement, not a define.

{
return x + y;
}

This way, I didn’t even need the add.cpp and it compiled just fine.
I think this is a compatibility error on behalf of Alex, since this guide was made for C++03 originally.

I am using Microsoft Visual Studio 2008. Created a win32 Console Application.

I have put the 3 files below. Main.cpp Class1.cpp and Class1.h
There seems to be a problem Linking but I can not figure out why.
Thanks a lot for your help, greatly appreciate your help.

FILE: MAIN.cpp_____________________________________________

#include
#include
#include “Class1.h”
int main()
{
Class1 c;
int res=c.add(3, 4);
return 0;
}
_____________________________________________
FILE: Class1.cpp_____________________________________________
#include

class Class1
{
public:
int add(int x, int y)
{
return x + y;
}
};

_____________________________________________
FILE:Class1.h_____________________________________________
#ifndef CLASS1_H
#define CLASS1_H

class Class1
{
public:
int add(int x, int y); // function prototype
};

#endif