Steps to write a basic window program with C and Win32 APIs.

Basic steps in Win32 Application

A standard windows program contains the following minimal steps:

  1. Define a Custom Window Class- Define your own window class,
  2. Register the Window Class - Register your class so that you can use the name with CreateWindow() call,
  3. Create the registered window - Create the main overlapped window,
  4. Show and Update Window - Show and update the window as per user's show value,
  5. Define a WndProc() callback for this the window - This call back should handle all necessary messages and must pass those messages to DefWindowProc() which it is not handling. This message handler should also have a exit path like when user exits the window by clicking cross button or Alt+F4 from the keyboard,
  6. Wait for the user messages and dispatch - An infinite loop fetches messages from message queue and dispatch it to window procedure.

Source Code

#include <windows.h>

LRESULT CALLBACK WndProc(HWND hWnd,
                         UINT message, 
                         WPARAM wParam,
                         LPARAM lParam);

int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
{
  WNDCLASS wc;
  MSG msg;
  HWND hWnd;
  ZeroMemory(&wc, sizeof(WNDCLASS));

  wc.style           = CS_HREDRAW | CS_VREDRAW;
  wc.lpfnWndProc     = (WNDPROC)WndProc;
  wc.hInstance       = hInstance;
  wc.hCursor         = LoadCursor(NULL, IDC_ARROW);
  wc.hbrBackground   = (HBRUSH)(COLOR_BACKGROUND);
  wc.lpszClassName   = (LPCTSTR)"MyBasicWin32Class";


  RegisterClass(&wc);

  hWnd = CreateWindow("MyBasicWin32Class",
                      "Basic steps Win32 App",
                      WS_OVERLAPPEDWINDOW,
                      CW_USEDEFAULT,
                      0,
                      CW_USEDEFAULT,
                      0,
                      NULL,
                      NULL,
                      hInstance,
                      NULL);

  ShowWindow(hWnd, nCmdShow);
  UpdateWindow(hWnd);
  while (GetMessage(&msg, NULL, 0, 0)) 
  {
    DispatchMessage(&msg);
  }
  return 0;
}

LRESULT CALLBACK WndProc(HWND hWnd,
                         UINT message,
                         WPARAM wParam,
                         LPARAM lParam)
{
  switch (message) 
  {
    case WM_DESTROY:
      PostQuitMessage(0);
      break;
    default:
      return DefWindowProc(hWnd, message, wParam, lParam);
   }
   return 0;
}

Program output

basic win32 application window

About our authors: Team EQA

Further readings

Where is WinMain() function in MFC application ?

MFC hides WinMain in its framework and includes source file on WinMain(). This explains how framework calls global CWinApp::Initinstance() from entry WinMain.

What is the utility of CWinApp class?

This is constructed during global C++ objects are constructed and is already available when Windows calls the WinMain function, which is supplied by the ...

Basic steps in Win32 GUI Application with source code.

Define a custom Window class structure, Register the class name, CreateWindow, Show windows and write message get and dispatch loop statements. Define the Window CallBack procedure and write the handlers.

What is a Window CallBack procedure and what is its utility?

DispatchMessage() is a API which indirectly triggers the Window CallBack procedure. Message structure members from this function are passed to the CallBack procedure. CallBack procedure should implement event handlers depending on the need of the application.

What are LPARAM and WPARAM in window proc function?

LPARAM and WPARAM are the two parameters in Window CallBack procedure. They signifies parameters of various events. They are used in handing individual events.

What are the basic steps of a typical MFC based application?

We need to write WinMain and need to follow all these in a Win32 application. However we need not to write much if we are writing an application with MFC ...

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