constructor mismatch parameter and argument

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VisualC++

I have a doubt that CIAlert has constructor with more than one parameters, but while executing the constructor only one argument is passed. How is it possible , Can any one explain how the below program works?

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#ifdef _ASGDLL
#define ASGDLL_EXP __declspec(dllexport)
#else
#define ASGDLL_EXP __declspec(dllimport)
#endif

class ASGDLL_EXP CIAlert
{

// Constructors
public:
    CIAlert(WORD wCategoryParam, LPCTSTR lpszSourceName = PROJECT_ERROR_SOURCE,  LPCTSTR lpszMsgsModuleName = PROJECT_ERROR_MSG_SOURCE);

// Destructors
public:
    virtual ~CIAlert();

}


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#define C_STOREUPD_MAIN                  ((DWORD)0x000000FAL)

int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
{
    CIAlert alert(C_STOREUPD_MAIN);
    int nRetCode = 0;
}

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