Windows API C++ Hello World Application

#define WIN32_LEAN_AND_MEAN
#include 

int WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR, int);
bool CreateMainWindow(HINSTANCE, int);
LRESULT WINAPI WinProc(HWND, UINT, WPARAM, LPARAM);

HINSTANCE hinst;

const char CLASS_NAME[] = "WinMain";
const char APP_TITLE[] = "Hello World";
const int WINDOW_WIDTH = 400;
const int WINDOW_HEIGHT = 400;

int WINAPI WinMain(HINSTANCE hInstance,
       HINSTANCE hPrevInstance,
       LPSTR lpCmdLine,
       int nCmdShow) {
  
  MSG msg;

  if(!CreateMainWindow(hInstance, nCmdShow)) {
   return false;
  }

  int done = 0;
  while(!done) {
   if(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
    if(msg.message == WM_QUIT) {
     done = 1;
    }

    TranslateMessage(&msg);
    DispatchMessage(&msg);
   }
  }

  return msg.wParam;
}

LRESULT WINAPI WinProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) {
 switch(msg) {
  case WM_DESTROY:
   PostQuitMessage(0);
   return 0;
 }
 return DefWindowProc(hWnd, msg, wParam, lParam);
}

bool CreateMainWindow(HINSTANCE hInstance, int nCmdShow) {
 WNDCLASSEX wcx;
 HWND hwnd;

 wcx.cbSize = sizeof(wcx);
 wcx.style = CS_HREDRAW | CS_VREDRAW;
 wcx.lpfnWndProc = WinProc;
 wcx.cbClsExtra = 0;
 wcx.cbWndExtra = 0;
 wcx.hInstance = hInstance;
 wcx.hIcon = NULL;
 wcx.hCursor = LoadCursor(NULL, IDC_ARROW);

 wcx.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
 wcx.lpszMenuName = NULL;
 wcx.lpszClassName = CLASS_NAME;
 wcx.hIconSm = NULL;

 if(RegisterClassEx(&wcx) == 0) {
  return false;
 }

 hwnd = CreateWindow(CLASS_NAME,
       APP_TITLE,
       WS_OVERLAPPEDWINDOW,
       CW_USEDEFAULT,
       CW_USEDEFAULT,
       WINDOW_WIDTH,
       WINDOW_HEIGHT,
       (HWND) NULL,
       (HMENU) NULL,
       hInstance,
       (LPVOID) NULL);
 if(!hwnd) {
  return false;
 }

 ShowWindow(hwnd, nCmdShow);
 UpdateWindow(hwnd);
 return true;
}