this code creates a window

// test4c.cpp : Defines the entry point for the application.
//
#define _CRT_SECURE_NO_WARNINGS

#include "framework.h"
#include "test4c.h"
#include <stdio.h>

#define MAX_LOADSTRING 100
#define ID_EDIT1 1
#define ID_EDIT2 2
#define ID_BUTTON 3

// Global Variables:
HINSTANCE hInst;                                // current instance

HWND hEditBox1;
HWND hEditBox2;
HWND hButton;

// Forward declarations of functions included in this code module:
ATOM                MyRegisterClass(HINSTANCE hInstance);
BOOL                InitInstance(HINSTANCE, int);
LRESULT CALLBACK    WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK    About(HWND, UINT, WPARAM, LPARAM);

int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
                     _In_opt_ HINSTANCE hPrevInstance,
                     _In_ LPWSTR    lpCmdLine,
                     _In_ int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    // TODO: Place code here.

    // Initialize global strings
    MyRegisterClass(hInstance);

    // Perform application initialization:
    if (!InitInstance (hInstance, nCmdShow))
    {
        return FALSE;
    }


    MSG msg;

    // Main message loop:
    while (GetMessage(&msg, nullptr, 0, 0))
    {
        if (!TranslateMessage(&msg))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }

    return (int) msg.wParam;
}

//
//  FUNCTION: MyRegisterClass()
//
//  PURPOSE: Registers the window class.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
    WNDCLASSEXW wcex;

    wcex.cbSize = sizeof(WNDCLASSEX);

    wcex.style          = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc    = WndProc;
    wcex.cbClsExtra     = 0;
    wcex.cbWndExtra     = 0;
    wcex.hInstance      = hInstance;
    wcex.hIcon          = LoadIcon(hInstance, IDI_WINLOGO);
    wcex.hCursor        = LoadCursor(nullptr, IDC_ARROW);
    wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW);
    wcex.lpszMenuName   = 0;
    wcex.lpszClassName  = L"MYWINDOW";
    wcex.hIconSm        = LoadIcon(hInstance, IDI_WINLOGO);

    return RegisterClassExW(&wcex);
}

//
//   FUNCTION: InitInstance(HINSTANCE, int)
//
//   PURPOSE: Saves instance handle and creates main window
//
//   COMMENTS:
//
//        In this function, we save the instance handle in a global variable and
//        create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
    hInst = hInstance; // Store instance handle in our global variable

    HWND hWnd = CreateWindowW(
        L"MYWINDOW",
        L"MYWINDOW",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, 0,
        319, 85,
        nullptr, nullptr,
        hInstance,
        nullptr
    );

    if (!hWnd)
    {
        return FALSE;
    }

    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);

    //ShowWindow(hEditBox1, nCmdShow);

    return TRUE;
}

//
//  FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
//  PURPOSE: Processes messages for the main window.
//
//  WM_COMMAND  - process the application menu
//  WM_PAINT    - Paint the main window
//  WM_DESTROY  - post a quit message and return
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_CREATE: {
        // edit box 1
        hEditBox1 = CreateWindowEx(
            WS_EX_CLIENTEDGE,
            L"EDIT",
            NULL,
            WS_BORDER | WS_VISIBLE | WS_CHILD | ES_LEFT,
            12, 12,
            89, 23,
            hWnd,
            (HMENU)ID_EDIT1,
            NULL,
            NULL
        );

        // text
        CreateWindow(
            L"STATIC",
            L"+",
            WS_VISIBLE | WS_CHILD | SS_LEFT,
            108, 15,
            15, 15,
            hWnd,
            NULL,
            NULL,
            NULL
        );

        // edit box 3
        hEditBox2 = CreateWindowEx(
            WS_EX_CLIENTEDGE,
            L"EDIT",
            NULL,
            WS_BORDER | WS_VISIBLE | WS_CHILD | ES_LEFT,
            125, 12,
            89, 23,
            hWnd,
            (HMENU)ID_EDIT2,
            NULL,
            NULL
        );

        // button
        hButton = CreateWindow(
            L"BUTTON",
            L"=",
            WS_VISIBLE | WS_CHILD,
            220, 12,
            75, 23,
            hWnd,
            (HMENU)ID_BUTTON,
            NULL,
            NULL
        );

        break;
    }
    case WM_PAINT:
        {
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hWnd, &ps);
            // TODO: Add any drawing code that uses hdc here...
            EndPaint(hWnd, &ps);
        }
        break;
    case WM_COMMAND: {
        if (LOWORD(wParam) == ID_BUTTON && HIWORD(wParam) == BN_CLICKED) {
            int len;
            wchar_t* wtext;
            char* text;

            len = GetWindowTextLengthW(hEditBox1);
            wtext = new wchar_t[len + 2];
            GetWindowTextW(hEditBox1, wtext, len + 1);
            text = new char[len + 1];
            sprintf(text, "%ws", wtext);
            int number1 = atoi(text);
            delete[] wtext;
            delete[] text;

            len = GetWindowTextLengthW(hEditBox2);
            wtext = new wchar_t[len + 2];
            GetWindowTextW(hEditBox2, wtext, len + 1);
            text = new char[len + 1];
            sprintf(text, "%ws", wtext);
            int number2 = atoi(text);
            delete[] wtext;
            delete[] text;

            char buf[256];
            sprintf(buf, "%d", number1 + number2);
            MessageBoxA(hWnd, buf, "Hi :)", MB_OK);
        }
        break;
    }
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}