C++ button Edit Label

#include <fstream>
#include <iostream>
#include <sstream>
#include <Windows.h>
#include <cstdio>
#include <string>
#include <cstring>
#include <tchar.h>
#include <stdlib.h>
#include <stdio.h>

// Copyright: rhouland@epastas.lt  &  evgeniistorozhev@mail.ru

LRESULT CALLBACK WndProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam) {

    static HWND HWNDStatic; // Label OutPut
    static HWND HWNDButton;
    static HWND HWNDButton2;
    static HWND HWNDButton3;
    static HWND HWNDEdit1;
    static HWND HWNDEdit2;

    switch(Message) {

        case WM_DESTROY: {
            PostQuitMessage(0);
            break;
        }

        case WM_CREATE: {

        CreateWindow(TEXT("STATIC"),TEXT(" Enter Digit A : "),
        WS_VISIBLE | WS_CHILD | SS_CENTER | SS_CENTERIMAGE,
        110,30,170,32,hwnd,(HMENU)1,NULL,NULL );

        HWNDEdit1 = CreateWindow(TEXT("edit"),TEXT(""),
        WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER,
        310,35,170,20,hwnd,(HMENU)2,NULL,NULL);

        CreateWindow(TEXT("STATIC"),TEXT(" Enter Digit B : "),
        WS_VISIBLE | WS_CHILD | SS_CENTER | SS_CENTERIMAGE,
        110,70,170,32,hwnd,(HMENU)3,NULL,NULL );

        HWNDEdit2 = CreateWindow(TEXT("edit"),TEXT(""),
        WS_VISIBLE | WS_CHILD | WS_BORDER | SS_CENTER,
        310,75,170,20,hwnd,(HMENU)4,NULL,NULL);

        HWNDButton = CreateWindow(TEXT("button"),TEXT(" Call A + B "),
        WS_VISIBLE | WS_CHILD,
        80,120,130,35,hwnd,(HMENU) 5,NULL,NULL );

        HWNDButton2 = CreateWindow(TEXT("button"),TEXT(" Call A * B "),
        WS_VISIBLE | WS_CHILD,
        240,120,130,35,hwnd,(HMENU) 8,NULL,NULL );

        HWNDButton3 = CreateWindow(TEXT("button"),TEXT(" Call A / B "),
        WS_VISIBLE | WS_CHILD,
        390,120,130,35,hwnd,(HMENU) 9,NULL,NULL );

        HWNDStatic = CreateWindow(TEXT("STATIC"),TEXT(" .... "),
        WS_VISIBLE | WS_CHILD | SS_CENTER | SS_CENTERIMAGE,
        250,200,90,22,hwnd,(HMENU)6,NULL,NULL);

        CreateWindow(TEXT("button"), TEXT("Exit!"),
        WS_VISIBLE | WS_CHILD | SS_CENTER,
        250,300,90,35,hwnd, (HMENU) 7, NULL, NULL);

        CreateWindow(TEXT("button"), TEXT("Clear All!"),
        WS_VISIBLE | WS_CHILD | SS_CENTER,
        220,240,160,35,hwnd, (HMENU) 10, NULL, NULL);

        case WM_COMMAND: // Dead programm!
        if (LOWORD(wParam) == 7)
        {
        PostQuitMessage(0);
        }

        if (LOWORD(wParam) == 5) // Call A + B
        {

        char hhh[400];
        int vt=16;
        GetWindowText( HWNDEdit1, hhh, vt );
        double aaa = atof(hhh);

        char yyy[400];
        int vtf=16;
        GetWindowText( HWNDEdit2, yyy, vtf );
        double bbb = atof(yyy);

        double fn1=aaa, fn2=bbb, fn3=fn1+fn2;
        std::ostringstream ss;
        ss << fn3;
        SetWindowText(HWNDStatic, ss.str().c_str());
        SetWindowText(HWNDButton, "Result A + B ");
        SetWindowText(HWNDButton2, "Call A * B ");
        SetWindowText(HWNDButton3, "Call A / B ");
        }

        if (LOWORD(wParam) == 8) // Call A * B
        {

        char hhh[400];
        int vt=16;
        GetWindowText( HWNDEdit1, hhh, vt );
        double aaa = atof(hhh);

        char yyy[400];
        int vtf=16;
        GetWindowText( HWNDEdit2, yyy, vtf );
        double bbb = atof(yyy);

        double fn1=aaa, fn2=bbb, fn3=fn1*fn2;
        std::ostringstream ss;
        ss << fn3;
        SetWindowText(HWNDStatic, ss.str().c_str());
        SetWindowText(HWNDButton2, "Result A * B ");
        SetWindowText(HWNDButton, "Call A + B ");
        SetWindowText(HWNDButton3, "Call A / B ");
        }

        if (LOWORD(wParam) == 9) // Call A / B
        {

        char hhh[400];
        int vt=16;
        GetWindowText( HWNDEdit1, hhh, vt );
        double aaa = atof(hhh);

        char yyy[400];
        int vtf=16;
        GetWindowText( HWNDEdit2, yyy, vtf );
        double bbb = atof(yyy);

        double fn1=aaa, fn2=bbb, fn3=fn1/fn2;
        std::ostringstream ss;
        ss << fn3;
        SetWindowText(HWNDStatic, ss.str().c_str());
        SetWindowText(HWNDButton3, "Result A / B ");
        SetWindowText(HWNDButton, "Call A + B ");
        SetWindowText(HWNDButton2, "Call A * B ");
        }

        if (LOWORD(wParam) == 10) // Clear all
        {
        SetWindowText(HWNDStatic, " .... ");
        SetWindowText(HWNDButton3, "Call A / B ");
        SetWindowText(HWNDButton, "Call A + B ");
        SetWindowText(HWNDButton2, "Call A * B ");
        SetWindowText(HWNDEdit1, "");
        SetWindowText(HWNDEdit2, "");
        }

        }
        default:
        return DefWindowProc(hwnd, Message, wParam, lParam);
    }

    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
    setlocale(LC_ALL, "Lithuanian");
    WNDCLASSEX wc;
    HWND hwnd;
    MSG msg;

    memset(&wc,0,sizeof(wc));
    wc.cbSize        = sizeof(WNDCLASSEX);
    wc.lpfnWndProc   = WndProc;
    wc.hInstance     = hInstance;
    wc.hCursor       = LoadCursor(NULL, IDC_ARROW);

    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wc.lpszClassName = "WindowClass";
    wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
    wc.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

    if(!RegisterClassEx(&wc)) {
        MessageBox(NULL, "Window Registration Failed!","Error!",MB_ICONEXCLAMATION|MB_OK);
        return 0;
    }

    hwnd = CreateWindowEx(WS_EX_CLIENTEDGE,"WindowClass","Butt-Lbl-Out",WS_VISIBLE|WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        640,480,NULL,NULL,hInstance,NULL);

    if(hwnd == NULL) {
        MessageBox(NULL, "Window Creation Failed!","Error!",MB_ICONEXCLAMATION|MB_OK);
        return 0;
    }

    while(GetMessage(&msg, NULL, 0, 0) > 0) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}