class definition error

I am writting a simply inheritance test program. Master class is dad class. class son and daughter is derieved from dad.

my code :
dad.h

Code:

---

#include <iostream>
using namespace std;
class dad{
protected:
    string name;
public:
    dad(string);
        dad();
};

---

dad.cpp

Code:

---

#include <iostream>
#include "dad.h"
using namespace std;
dad::dad(){
}
dad::dad(string r){
    name=r;
}

---

son.h

Code:

---

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

class son:public dad{
private:
    int age;
public:
    son(string,int);
};

---

son.h

Code:

---

#include <iostream>
#include "dad.h"
using namespace std;
class son:public dad{
private:
    int age;
public:
    son(string,int);
};

---

son.cpp

Code:

---

#include <iostream>
#include "son.h"
using namespace std;
son::son(string r,int x){
    name=r;
    age=x;
}

---

daughter.h

Code:

---

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

using namespace std;

class daughter:public dad{
private:
    int age;
public:
    daughter(string,int);
};

---

daughter.cpp

Code:

---

#include <iostream>
#include "daughter.h"
using namespace std;
daughter::daughter(string r,int x){
    name=r;
    age=x;
}

---

main.cpp

Code:

---

#include <cstdlib>
#include <iostream>

#include "son.h"
#include "daughter.h"


using namespace std;

int main(int argc, char *argv[])
{       
        system("PAUSE");
    return EXIT_SUCCESS;
}

---

i compile the project in visual c++. i get this error::
"Error 1 error C2011: 'dad' : 'class' type redefinition"

how to over come it? looks like a small error,but i aint able to figure it out.pls help.thanks,.

If the contents of a source file is #include'd more than once (directly or indirectly) the compiler seems multiple definitions of any classes. That's a violation of the one-definition rule.

Common practice is to employ include guards on all headers of the form;

Code:

---

#ifndef SOME_MACRO_UNIQUE_TO_THIS_HEADER_FILE
#define SOME_MACRO_UNIQUE_TO_THIS_HEADER_FILE

//  the content you have in the header file

#endif

---

You need to employ some consistent approach to ensure no two header files use the same macro for their include guard.

Your header don't have include guards. So, if you include both "daughter.h" and "son.h", the declaration of the dad class gets included twice.

Code:

---

#ifndef SOME_IDENTIFIER_EG_HEADERS_FILENAME_H
#define SOME_IDENTIFIER_EG_HEADERS_FILENAME_H

class X
{
...
};

#endif

---

You may also be misunderstanding what inheritance is in programming. Does it make sense to say that "son is a kind of dad" and "daughter is a kind of dad"?

Quote:

---

Originally Posted by anon

You may also be misunderstanding what inheritance is in programming. Does it make sense to say that "son is a kind of dad" and "daughter is a kind of dad"?

---

However, legally, sons and daughters expect to inherit from their parents. And they can also be said to inherit characteristics.

But, yeah, these meanings of inheritence differ from the meaning employed in object oriented design, in which "inherits" means "is a kind of".

Another problem is that you are including the wrong header file.
std::string uses the <string> header file, not the <iostream> header file.
It's also bad practice to put "using namespace" lines in a header file.