Калькулятор на С++

#include "Calc.h"
#include <math.h>
 
//---------------------------------------------------------------------------
 
#pragma package(smart_init)
  
 
//***************************   ADD  *********************
float CCalc::Add(float operand_1, float operand_2)
{
  return (operand_1+operand_2);
}
//************************end   ADD  *********************
 
 
//***************************   MUL  *********************
float CCalc::Mul(float operand_1, float operand_2)
{
  return (operand_1*operand_2);
}
//************************end   MUL  *********************
 
//***************************   VID  *********************
float CCalc::Vid(float operand_1, float operand_2)
{
  return (operand_1-operand_2);
}
//************************end   VID  *********************
 
//***************************   DIL  *********************
float CCalc::Dil(float operand_1, float operand_2)
{
  if (operand_2!=0)
    return (operand_1/operand_2);
  else
    return 0;
}
//************************end   DIL  *********************
 
 
//***************************   Sqrt *********************
float CSuperCalc::Sqrt(float operand_1)
{
  return (sqrt(operand_1));
}
//************************end   Sqrt *********************
 
//***************************   PlusMinus  *********************
float CSuperCalc::PlusMinus(float operand_1)
{
  return (PlusMinus(operand_1));
}
//************************end   PlusMinus  *********************
 
//***************************   Sqr  *********************
float CSuperCalc::Sqr(float operand_1)
{
  return (operand_1*operand_1);
}
//************************end   Sqr  *********************
 
//***************************   Sqr  *********************
float CSuperCalc::Sqrw(float operand_1)
{
  return (operand_1*operand_1*operand_1);
}
//************************end   Sqr  ********************

#include "stdafx.h"
#include <windows.h>
LRESULT CALLBACK HelloWorldWndProc(HWND, UNIT, UNIT, LONG);
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR IpszCmdParam, int nCmdShow)
{
    HWND hWND;
    WNDCLASS WndClass;
    MSG Msg;
    char szClassName[] = "Hello World!!";
    /*Регистрируем создаваемый класс*/
    /*заполняем структуру типа класс*/
    WndClass.style=CS_HREDRAW|CS_VREDRAW;
    WndClass.lpfnWndProc=HelloWorldWndProc;
    WndClass.cbClsExtra=0;
    WndClass.cbWndExtra=0;
    WndClass.hInstance=hInstance;
    WndClass.hIcon=LoadIcon(NULL, IDI_APPLICATION);
    WndCLass.hCursor=LoadCursor(NULL, IDC_ARROW);
    WndClass.hbrBackground=(HBRUSH) GetStockObject(WHITE_BRUSH);
    WndClass.lpszMenuName=NULL;
    WndClass.lpszClassName=szClassName;
 
    if (!RegisterClass(&WndClass))
    {
        MessageBox(NULL,"Cannot register class","Error",MB_OK);
        return 0;
    }
    hWnd=CreateWindow(szClassName, "Program No 1", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT,CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDDEFAULT,NULL,NULL,hInstance,NULL);
    if (!hWnd)
    {
        MessageBox(NULL,"Cannot create window", "Error",MB_OK);
        return 0;
    }
        /*Show our window*/
        ShowWindow(hWnd,nCmdShow);
        UpdateWindow(hWnd);
 
        /*Beginning of messages cycle*/
        while (GetMessage(&Msg, NULL,0,0))
        {
            TranseteMessage(&Msg);
            DispatchMessage(&Msg);
        }
        return Msg.wParam;
}
    LRESULT CALLBACK HelloWorldWndProc(HWND hWnd, UNIT Message, UNIT wParam, LONG IParam)
    {
        HDC hDC;
        PAINTSTRUCT PaintStruct;
        RECT Rect;
        switch(Message)
        {
        case WM_PAINT:
                hDC=BeginPaint(hWnd, &PaintStruct);
                GetClientRect(hWnd, &Rect);
                WrawText(hDC,"Hello World!!", -1, &Rect, DT_SINGLELINE|DT_CENTER|DT_VCENTER);
                EndPaint(hWnd,&PaintStruct);
                return 0;
        case WM_DESTROY:
                PostQuitMessage(0);
                return 0;
        }
        return DefWindowProc(hWnd,Message,wParam,IParam);

private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
             
             Display->Text=Display->Text+"1";
            float a;
            a=(float)atof(Display->Text);
}