WinMain

Description

The user-provided entry point for a graphical Windows-based application.

WinMain is the conventional name used for the application entry point.

Syntax

int CALLBACK WinMain(
  _In_  HINSTANCE hInstance,
  _In_  HINSTANCE hPrevInstance,
  _In_  LPSTR lpCmdLine,
  _In_  int nCmdShow
);

Parameters

hInstance [in]

Type: HINSTANCE

A handle to the current instance of the application.

hPrevInstance [in]

Type: HINSTANCE

A handle to the previous instance of the 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 function will return ERROR_ALREADY_EXISTS. This indicates that another instance of your application exists, because it created the mutex first. However, a malicious user can create this mutex before you do and prevent your application from starting. To prevent this situation, create a randomly named mutex and store the name so that it can only be obtained by an authorized user. Alternatively, you can use a file for this purpose. To limit your application to one instance per user, create a locked file in the user's profile directory.

lpCmdLine [in]

Type: LPSTR

The command line for the application, excluding the program name. To retrieve the entire command line, use the GetCommandLine function.

nCmdShow [in]

Type: int

Controls how the window is to be shown. This parameter can be one of the following values.

Value	Meaning
SW_HIDE 0	Hides the window and activates another window.
SW_MAXIMIZE 3	Maximizes the specified window.
SW_MINIMIZE 6	Minimizes the specified window and activates the next top-level window in the Z order.
SW_RESTORE 9	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 5	Activates the window and displays it in its current size and position.
SW_SHOWMAXIMIZED 3	Activates the window and displays it as a maximized window.
SW_SHOWMINIMIZED 2	Activates the window and displays it as a minimized window.
SW_SHOWMINNOACTIVE 7	Displays the window as a minimized window. This value is similar to SW_SHOWMINIMIZED, except the window is not activated.
SW_SHOWNA 8	Displays the window in its current size and position. This value is similar to SW_SHOW, except the window is not activated.
SW_SHOWNOACTIVATE 4	Displays a window in its most recent size and position. This value is similar to SW_SHOWNORMAL, except the window is not activated.
SW_SHOWNORMAL 1	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 value

Type:

Type: int

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.

Example

#include <windows.h>

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, 
    LPSTR lpCmdLine, int nCmdShow)
{
    MessageBox(NULL, "Hello world!", "Hello", MB_OK);
    return 0;
}