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 WinMain

The WinMain function is called by the system as the initial entry point for a Win32-based application.

    int WINAPI WinMain(
      HINSTANCE hInstance,      // handle to current instance
      HINSTANCE hPrevInstance,  // handle to previous instance
      LPSTR lpCmdLine,          // command line
      int nCmdShow              // show state
    );

Parameters

• hInstance
  [in] Handle to the current instance of the application.
• hPrevInstance
  [in] Handle to the previous instance of the application. For a Win32-based application, this parameter is always NULL. If you need to detect whether another instance already exists, create a uniquely named mutex using the CreateMutex function. CreateMutex will succeed even if the mutex already exists, but the GetLastError function will return ERROR_ALREADY_EXISTS. This indicates that another instance of your application exists, because it created the mutex first.
• lpCmdLine
  [in] Pointer to a null-terminated string specifying the command line for the application, excluding the program name. To retrieve the entire command line, use the GetCommandLine function.
• nCmdShow
  [in] Specifies how the window is to be shown. This parameter can be one of the following values. Value Meaning
  SW_HIDE Hides the window and activates another window. SW_MAXIMIZE Maximizes the specified window. SW_MINIMIZE Minimizes the specified window and activates the next top-level window in the Z order. SW_RESTORE Activates and displays the window. If the window is minimized or maximized, the system restores it to its original size and position. An application should specify this flag when restoring a minimized window. SW_SHOW Activates the window and displays it in its current size and position. SW_SHOWMAXIMIZED Activates the window and displays it as a maximized window. SW_SHOWMINIMIZED Activates the window and displays it as a minimized window. SW_SHOWMINNOACTIVE Displays the window as a minimized window. This value is similar to SW_SHOWMINIMIZED, except the window is not activated. SW_SHOWNA Displays the window in its current size and position. This value is similar to SW_SHOW, except the window is not activated. SW_SHOWNOACTIVATE Displays a window in its most recent size and position. This value is similar to SW_SHOWNORMAL, except the window is not actived. SW_SHOWNORMAL Activates and displays a window. If the window is minimized or maximized, the system restores it to its original size and position. An application should specify this flag when displaying the window for the first time.

Return Values

If the function succeeds, terminating when it receives a WM_QUIT message, it should return the exit value contained in that message's wParam parameter. If the function terminates before entering the message loop, it should return zero.

Remarks

Your WinMain should initialize the application, display its main window, and enter a message retrieval-and-dispatch loop that is the top-level control structure for the remainder of the application's execution. Terminate the message loop when it receives a WM_QUIT message. At that point, your WinMain should exit the application, returning the value passed in the WM_QUIT message's wParam parameter. If WM_QUIT was received as a result of calling PostQuitMessage, the value of wParam is the value of the PostQuitMessage function's nExitCode parameter. For more information, see Creating a Message Loop.

ANSI applications can use the lpCmdLine parameter of the WinMain function to access the command-line string, excluding the program name. The reason that WinMain cannot return Unicode strings is that lpCmdLine uses the LPSTR data type, not the LPTSTR data type. The GetCommandLine function can be used to access Unicode strings in the command line, because it uses the LPTSTR data type.

Requirements

• Windows NT/2000 or later: Requires Windows NT 3.1 or later.
• Windows 95/98/Me: Requires Windows 95 or later.
• Header: Declared in Winbase.h; include Windows.h.

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Notebook exported on Monday, 7 July 2008, 18:56:50 PM Eastern Daylight Time