[SDL] error with 'multiple definition'

[nathayan de los valles]

Hi all,
Perhaps this is not the best place to throw my doubt... but I have no 
friends who can answer me.
I am using C++ and SDL.
I have several files .h like this:
A.h
#ifndef A_H
#define A_H
#include <iostream>
#include <sstream>
#include <string>
#include <fstream>
std::string rem = "//";
//more definitions
#endif

B.h
#ifndef B_H
#define B_H
#include "A.h"
//definitions
#endif

My compiler says me:   multiple definition of 'rem'. I think my compiler 
doesn't run properly. Any idea?

I use:
Dev C++ 4.9.9.2 (I know there is more interesting information but I don't 
remember where to find it).
Thanks in advance.

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