Header Files for DLLArith

//DLLArith - These are all in the Header Files or DLLArith
//Add.h
#ifndef __ADD_H__
#define __ADD_H__

#include "IArith.h"

class Add : public IArith
{
public:
    // Only declare member function
    int Calc(int v1, int v2);
};


#endif
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//DLLArith.h
#ifndef __DLLTEST_H__
#define __DLLTEST_H__

#ifdef DLL_EXPORT
#define DLLTEST_API __declspec (dllexport)
#else
#define DLLTEST_API __declspec (dllimport)
#endif

#include "IArith.h"

extern "C"
{
    DLLTEST_API IArith* NewObject(int operation);
    DLLTEST_API void DelObject(IArith *pObject);
}

#endif
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//IArith.h
#ifndef __IARITH_H__
#define __IARITH_H__

class IArith
{
public:
    virtual int Calc(int v1, int v2) = 0;
};


#endif
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// subtract.h
#ifndef __SUBTRACT_H__
#define __SUBTRACT_H__

#include "IArith.h"

class Subtract : public IArith
{
public:
    // Only declare member function
    int Calc(int v1, int v2);
};
#endif