C / C++ / MFC

// C++ only

class SavingsAccount
{
public:
   static void setInterest( float newValue )  // Member function
      { currentRate = newValue; }             //    that accesses
                                              //    only static
                                              //    members
private:
   char name[30];
   float total;
   static float currentRate;    // One copy of this member is
                                //    shared among all instances
                                //    of SavingsAccount
};

// Static data members must be initialized at file scope, even
//    if private.
float SavingsAccount::currentRate = 0.00154;

Tracker.obj : error LNK2005: "private: static float  SavingsAccount::currentRate" (?currentRate@SavingsAccount@@0MA) already defined in Capture.obj
Tracker.obj : error LNK2005: "protected: static int  CTracker::a" (?a@CTracker@@1HA) already defined in Capture.obj
Tracker.obj : warning LNK4006: "private: static float  SavingsAccount::currentRate" (?currentRate@SavingsAccount@@0MA) already defined in Capture.obj; second definition ignored

long WINAPI WindowProc(HWND hWnd, UINT wMessage, WPARAM wParam, LPARAM lParam)
{
    return DefWindowProc(hWnd, wMessage, wParam, lParam);
}

void CreateLogWindow()
{
	static char szAppName[] = "LogWindow" ;
	
	HWND		hWnd;
	WNDCLASS	WndClass;

	WndClass.style = CS_HREDRAW | CS_VREDRAW;
	WndClass.lpfnWndProc = WindowProc;
	WndClass.cbClsExtra = 0;
	WndClass.cbWndExtra = 0;
	WndClass.hbrBackground = (HBRUSH) GetStockObject(LTGRAY_BRUSH);
	WndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
	WndClass.hIcon = 0;
	WndClass.hInstance = hInstance;
	WndClass.lpszClassName = "Testprogramm";
	WndClass.lpszMenuName = NULL;

	RegisterClass(&WndClass);

	hWnd = CreateWindow(
		"LogWindow",
		"LogWindow",
		WS_CAPTION | WS_THICKFRAME | WS_VISIBLE,
		0,
		0,
		250,//GetSystemMetrics(SM_CXSCREEN),
		250,//GetSystemMetrics(SM_CYSCREEN),
		NULL,
		NULL,
		hInstance,
		NULL
	);

	ShowWindow(hWnd, SW_SHOW);
	UpdateWindow(hWnd);
	SetFocus(hWnd);
}