Project setup in Visual Studio

• File → New → Project
• Select "Installed" → "C++" → "Windows Desktop" → "Windows Desktop Wizard" (or "Win32 Project" on older VS)
• Name the project (for example, MinimalWin32App)
• Choose "Windows application" and check "Empty project" (no ATL/MFC, no precompiled header if you prefer manual setup)
• Add a new C++ source file (e.g., main.cpp)

Required headers

At minimum, include the Win32 API definitions.

#include <windows.h>

Modern Visual Studio defaults to Unicode. The code below uses wide-character (W) APIs.

Entry point and program flow

A GUI Win32 program starts from WinMain or wWinMain. The core steps are:

• Define and register a window class (WNDCLASSEX)
• Create the main window
• Show and udpate the window
• Run the message loop
• Handle messages in a window procedure (WndProc)

Complete minimal example

The following self-contained program creates a window and paints "Hello, Windows!" centerde in the client area.

#include <windows.h>

// Window procedure declaration
LRESULT CALLBACK WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);

int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE, PWSTR, int nCmdShow) {
    // 1) Register a window class
    const wchar_t kClassName[]   = L"MinimalWin32WindowClass";
    const wchar_t kWindowTitle[] = L"Minimal Win32 Window";

    WNDCLASSEXW wc{};
    wc.cbSize        = sizeof(wc);
    wc.style         = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc   = WindowProc;
    wc.cbClsExtra    = 0;
    wc.cbWndExtra    = 0;
    wc.hInstance     = hInstance;
    wc.hIcon         = LoadIconW(nullptr, IDI_APPLICATION);
    wc.hCursor       = LoadCursorW(nullptr, IDC_ARROW);
    wc.hbrBackground = reinterpret_cast<HBRUSH>(COLOR_WINDOW + 1);
    wc.lpszMenuName  = nullptr;
    wc.lpszClassName = kClassName;
    wc.hIconSm       = wc.hIcon;

    if (!RegisterClassExW(&wc)) {
        MessageBoxW(nullptr, L"RegisterClassExW failed", L"Error", MB_ICONERROR);
        return 0;
    }

    // 2) Create the window
    HWND hwnd = CreateWindowExW(
        0,
        kClassName,
        kWindowTitle,
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT,
        640, 240,
        nullptr,
        nullptr,
        hInstance,
        nullptr
    );

    if (!hwnd) {
        MessageBoxW(nullptr, L"CreateWindowExW failed", L"Error", MB_ICONERROR);
        return 0;
    }

    // 3) Show and update the window
    ShowWindow(hwnd, nCmdShow);
    UpdateWindow(hwnd);

    // 4) Message loop
    MSG msg{};
    while (GetMessageW(&msg, nullptr, 0, 0) > 0) {
        TranslateMessage(&msg);
        DispatchMessageW(&msg);
    }
    return static_cast<int>(msg.wParam);
}

// 5) Window procedure: handle paint and destroy
LRESULT CALLBACK WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    switch (msg) {
        case WM_PAINT: {
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hwnd, &ps);

            RECT rc;
            GetClientRect(hwnd, &rc);
            SetBkMode(hdc, TRANSPARENT);
            SetTextColor(hdc, RGB(32, 32, 32));
            const wchar_t* text = L"Hello, Windows!";
            DrawTextW(hdc, text, -1, &rc, DT_SINGLELINE | DT_CENTER | DT_VCENTER);

            EndPaint(hwnd, &ps);
            return 0;
        }
        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
        default:
            return DefWindowProcW(hwnd, msg, wParam, lParam);
    }
}

Key building blocks

• WNDCLASSEX: Describes the window type (procedure function, background brush, cursor, icons, style, and class name). Registration with RegisterClassExW makes the class available to CreateWindowExW.
• CreateWindowExW: Instantiates the top-level window using the registered class.
• ShowWindow/UpdateWindow: Makes the window visible and triggers an initial paint if needed.
• Message loop: Retrieves messages from the queue and routes them too the window procedure.
• Window procedure (WindowProc): Switches on message IDs. WM_PAINT uses BeginPaint/EndPaint to draw; WM_DESTROY posts the quit message.

Notes

• With Unicode builds, always call wide-character APIs (the W-suffixed versions) or rely on the TCHAR mapping if you prefer the generic macros.
• DrawTextW is used instead of TextOut to conveniently center text within the client rectangle.
• If project settings disable precompiled headers or additional libraries, ensure the subsystem is "Windows" and default libraries for User32/GDI32 are linked by the toolchain.