write a visual c program which can be associated with a certain file extension on windows and displays a custom message and an exit button
  Sure, here is an example of how you can create a simple visual C program that can be associated with a certain file extension on Windows and displays a custom message and an exit button:

1. Create a new Visual C project in Visual Studio or use an existing one.
2. In the project, add a new form to the project by going to "File" > "New" > "Form" or by using the shortcut "Ctrl + Shift + F".
3. In the form designer, add the following code to the form:
```
#include <windows.h>
#include <commdlg.h>

// Declare the form and its controls
DECLARE_DYNAMIC(MyForm, CDialog)

BEGIN_MESSAGE_MAP(MyForm, CDialog)
    ON_WM_CREATE()
    ON_WM_EXIT()
END_MESSAGE_MAP()

// Define the form's constructor and destructor
MyForm::MyForm() : CDialog(MyForm::IDD, MyForm::WMC_FULLSCREEN)
{
    // Initialize the form
}

MyForm::~MyForm()
{
    // Clean up the form
}

// Define the form's OnCreate and OnExit message handlers
ON_WM_CREATE()
{

// Visual C Program for Associating a File Extension with a Custom Message and Exit Button

#include <windows.h>

void customMessageAndExit(HWND hwnd, const char* customMessage, int exitCode)
{
    MessageBox(hwnd, customMessage, "Exit", MB_OK | MB_ICONEXIT);
    exit(exitCode);
}

int main()
{
    HWND hwnd;
    MSG msg;

    hwnd = CreateWindow("MyWindowClass", "My Window Title",
        WS_OVERLAPPEDWINDOW | WS_CAPTION,
        CW_USEDEFAULT, CW_USEDEFAULT,
        CW_USEDEFAULT, CW_USEDEFAULT,
        NULL, NULL, NULL, NULL);

    ShowWindow(hwnd, SW_SHOW);
    UpdateWindow(hwnd);

    while (true)
    {
        if (PeekMessage(&msg, hwnd, 0, 0, PM_REMOVE))
        {
            if (msg.message == WM_QUIT)
            {
                customMessageAndExit(hwnd, "Bye!", EXIT_SUCCESS);
                return 0;
            }
            else
