Creating a Button Outside a Dialog Box
The following example shows how to use the CreateWindow function to create a default push button.
hwndButton = CreateWindow(
"BUTTON", // predefined class
"OK", // button text
WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON, // styles
// Size and position values are given explicitly, because
// the CW_USEDEFAULT constant gives zero values for buttons.
10, // starting x position
10, // starting y position
100, // button width
100, // button height
hwnd, // parent window
NULL, // No menu
(HINSTANCE) GetWindowLong(hwnd, GWL_HINSTANCE),
NULL); // pointer not needed