Including header files

**Emeighty** · 08-09-2008

Hi all,

This may seem like an easy question to many of you, but this is troubling me a little. How do u include a header file. Can anyone spell it out like i have never seen c++ before. The books i have dont say much about it.

heres what i have made in dev C++

heres sample.h

Code:

#include<iostream>
using namespace std;

void sample(){

cout << "help" << endl;

}

and here i would assume is the implementation file trial.cpp

Code:

#include<iostream>

using namespace std;
#include "sample.h"

int main() 
{
    
    sample();
    
    
    system("Pause");
    
    return 0;
    
}

i get an error that says main is being redifined and its being defined here, but in the sample.h its not there.

also is there a certain location that need to have the files for this to work?

**Salem** · 08-09-2008

Are you sure that's the only sample.h you have?

Also, the code should be in sample.cpp, and the header file should just have
void sample( );

Header files are like the index of a book. They tell you what's available.

Then you have main.cpp and sample.cpp as files in the project.

**Emeighty** · 08-09-2008

Thanks a lot
I got it to work, but its a little unclear to me still. Here is the code that I changed to look like what you mentioned earlier

Sample.h

Code:

void sample();

sample.cpp

Code:

#include<iostream>
#include<sample.h>

using namespace std;
void sample(){

cout << "help" << endl;

}

trial.cpp

Code:

#include<iostream>

using namespace std;
#include "sample.cpp"

int main() 
{
    
    sample();
    
    
    system("Pause");
    
    return 0;
    
}

And one list thing. in order to include a file does it have to be after the namespace std; ? because when i put it in before it gives errors.
So this follows the spltting of files into 3 separate ones. implement, the code, and i forget the last one.

**Salem** · 08-09-2008

> #include "sample.cpp"
No, this is sample.h as well.

Then you add sample.cpp to the project.
Project->settings->source files.... (kinda thing)

If it were at the command line, it would be
g++ main.cpp sample.cpp

**Emeighty** · 08-09-2008

ahh, this was silly,

I had to create a project in dev C++, then i added trial.cpp and added sample.h to the project .

this it what i got.

trial.cpp

Code:

#include<iostream>

using namespace std;
#include "sample.h"

int main() 
{
    
    sample();
    
    
    system("Pause");
    
    return 0;
    
}

Code:

#include<iostream>


using namespace std;
void sample(){

cout << "help" << endl;

}

**cpjust** · 08-09-2008

Another thing to note (although in this simple example it doesn't matter), you should never put using statements in header files or before an #include statement; otherwise you could be changing the meaning of some of the code.

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