Making a header file(something I dont get)

I want to make some header files so I can organize my program a bit better. But im a little confused by it. Ive read the FAQ, some topics here on the forum,s and googled it. Everything I read says to make a new project with the extension '.h'. This is where i'm sonfused. It says to add like prototypes and stuff like that in here, and then the actual code to it in a .cpp file. Im confused because, how do you add prototypes to a file without giving it a .cpp file?

Are you supposed to make the '.h' file, add a .cpp and give it prototypes. Then make an empty project, give it a .cpp file, include the '.h' file and then just put the code that goes in your prototypes into the newly made .cpp file?

The stuff I read kept saying to put certain things in the '.h' file and other things in the .cpp file. But since nothing ever said that you have to make another project or anything I had no clue what to do heh.

(Im using DevC++ btw)

For Dev-C++, choose File->New source file and call it something.h. Add it to the same project.

As for what to put into a header file: basiclly you put prototypes in the header file, so that multiple .cpp files can include the header file and get the prototypes for the functions. You usually put the actual functions in a .cpp file.

A graphic example

Code:

---

// header file
#ifndef HEADER_H
#define HEADER_H

class Cat
{
public:
    Cat();
    ~Cat();

    int getAge() const;
    void setAge ( int age );

private:
    int *m_age;
};

#endif

---

Class implement file, note it will be the same name but uses .cpp not .h

Code:

---

#include "header.h"  // needed to acsess class

Cat::Cat()
{
    m_age = new int(2);
}

Cat::~Cat()
{
    delete m_age;
    m_age = NULL;
}

int Cat::getAge() const
{
    return *m_age;
}

void Cat::setAge ( int age )
{
    *m_age = age;

    return age;
}

---

main file follows

Code:

---

#include "header.h"
#include <iostream>

int main ( void )
{
    Cat *kitten = new Cat;

    std::cout << "My cat is " << kitten->getAge() << std::endl;

    kitten->setAge(3);

    std::cout << "Now my cat is " << kitten->getAge() << " years old" << std::endl;

    delete kitten;
    kitten = NULL;

    return 0;
}

---

Yoi can see that using header files you can split a large program up into more
managle peices

I tried doing this:

Code:

---

// header file
#ifndef HEADER_H // Im using HEADER just as an example, i gave it my own name
#define HEADER_H

void shop();

#endif

---

Code:

---

// .cpp for the shop()

#include "header.h"
#include <iostream>

// code for shop()

---

Code:

---

// Main .cpp

#include "header.h"
#include <iostream>

// Along with a few other includes and rest of program.

---

But that didnt work. Im guessing I did something wrong, but it looks basically the same to me.

That is the same. You must have done something different without realizing it.

What kind of errors are you getting? Or what?

Quote:

---

Originally Posted by FingerPrint

I tried doing this:

Code:

---

// header file
#ifndef HEADER_H // Im using HEADER just as an example, i gave it my own name
#define HEADER_H

void shop();

#endif

---

Code:

---

// .cpp for the shop()

#include "header.h"
#include <iostream>

// code for shop()

---

Code:

---

// Main .cpp

#include "header.h"
#include <iostream>

// Along with a few other includes and rest of program.

---

But that didnt work. Im guessing I did something wrong, but it looks basically the same to me.

---

WHAT didn't work? it failed to compile? the program crashed? it ran but sent porn to your girlfriend? DETAILS!!!

Well, I may have seen what I did wrong. But ill ask you guys real quick.

I make the header file IN my main program and just name it 'header.h' right?

When I try to compile and run it, it gets about a 1/3 of the way through the compilation then says:

Code:

---

Compiler: Default compiler
Building Makefile: "C:\Documents and Settings\Pamela Rowley\My Documents\My Pictures\b's folder\LoC\Makefile.win"
Executing  make...
make.exe -f "C:\Documents and Settings\Pamela Rowley\My Documents\My Pictures\b's folder\LoC\Makefile.win" all
g++.exe -D__DEBUG__ -c ../FirstGame/LoC2.0.cpp -o ../LoC/LoC2.0.o -I"C:/Dev-Cpp/lib/gcc/mingw32/3.4.2/include"  -I"C:/Dev-Cpp/include/c++/3.4.2/backward"  -I"C:/Dev-Cpp/include/c++/3.4.2/mingw32"  -I"C:/Dev-Cpp/include/c++/3.4.2"  -I"C:/Dev-Cpp/include"    -g3

../FirstGame/LoC2.0.cpp:11:25: myfunctions.h: No such file or directory
../FirstGame/LoC2.0.cpp: In function `int main()':
../FirstGame/LoC2.0.cpp:1631: error: `shop' undeclared (first use this function)

../FirstGame/LoC2.0.cpp:1631: error: (Each undeclared identifier is reported only once for each function it appears in.)

make.exe: *** [../LoC/LoC2.0.o] Error 1

Execution terminated

---

Also, it says shop() not declared. The original way I had it, it is declared, but with it this way it doesnt work.

Code:

---

../FirstGame/LoC2.0.cpp:11:25: myfunctions.h: No such file or directory

---

Are you sure you put

Code:

---

#include "myfunctions.h"

---

and not this?

Code:

---

#include <myfunctions.h>

---

Yes, im positive.

Well then myfunction.h doesn't exist, at least not in the same directory as the file you're including it from. Make sure it's in the right directory.

Here is what I have.

Code:

---

// Main file for entire program(beginning of it)

#include "myfunctions.h"

#include <iostream>
#include <stdlib.h>
#include <cstring>
#include <stdio.h>
#include <windows.h>
#include <fstream>
#include <time.h>
#include <string>

---

Code:

---

// the header file

#ifndef MYFUNCTIONS_H
#define MYFUNCTIONS_H 
// Im not sure on this. Since I have void shop(), should my
// #ifndef and #define both say SHOP_H instead?

void shop();

#endif

---

Code:

---

// the .cpp file for shop()
// this is only the beginning of it

#include "myfunctions.h"
#include <iostream>

---

Is that how it should be? And I am supposed to have the header file created like a .cpp file but just named header.h and it is supposed to be made in my main program file, correct? I dont make it as a seperate project or anything do I?

EDIT: I saved them all to the same folder(which is basically the same as the directory, no?)

Quote:

---

Is that how it should be? And I am supposed to have the header file created like a .cpp file but just named header.h and it is supposed to be made in my main program file, correct? I dont make it as a seperate project or anything do I?

---

That's right, it should be a file with a .h extension in the same directory as your .cpp file(s).

The only thing I can think of is that maybe your editor added an extension like .cpp to your file (to make it "myfunctions.h.cpp").

Code:

---

// the header file

#ifndef MYFUNCTIONS_H
#define MYFUNCTIONS_H 
// Im not sure on this. Since I have void shop(), should my
// #ifndef and #define both say SHOP_H instead?

void shop();

#endif

---

You can call the inclusion guards whatever you like, although it's usually related to the name of the file.

BTW, in C++, <stdlib.h> is <cstdlib>, and the same for all the standard .h files (excluding ones like windows.h).

Hmmm...I dont know what else to do. I dont get it, if the code is correct why isnt it working? Well, thanks for your help. Ill continue to work on it. If anyone happens to get a bright idea on whats wrong and how to fix it, please post! Thanks.

This error

Code:

---

../FirstGame/LoC2.0.cpp:11:25: myfunctions.h: No such file or directory

---

means that the compiler can't open the file. It (probably) doesn't exist. Whether it has the wrong extension or its sitting in the wrong directory or something else that I can't fathom, I don't know.

Open explorer and see if the .h file is in the right place with the right name.

If all else fails try putting the full path in your #include. (Don't keep it this way in case you move it or something, but it might be a good way to tell if it's working.) Something like this:

Code:

---

#include "c:/projects/myfunctions.h"

---

AHA! WOOT! I figured it out. I hadnt noticed it before, but they were actually saved in different directories. At some point I made the same file in 2 different places, and saved myfunctions.h to one and shop.cpp along with my main .cpp to the other one.

Its all good now heh.

wow this really helped

I am glad we could help - remeber practise makes perfect.

Once you get to understand how to create and link your own header files, you can organise
large projects much better, and not have to bung all the code in the one file. This makes it much easier to maintain and organise, and of course, other people will be able to find functions. classes better.

also,
<stdio.h> and <iostream> are the c and c++ versions of console output. You probably only want to use one of those and not both.

Or at least use the C++ namespace version, <cstdio>. (That applies for all the standard C header files, like <time.h> -> <ctime>.)