The CREATESTRUCT structure defines the initialization parameters passed to the window procedure of an application.

typedef struct tagCREATESTRUCT {  
    LPVOID lpCreateParams;  
    HANDLE hInstance;  
    HMENU hMenu;  
    HWND hwndParent;  
    int cy;  
    int cx;  
    int y;  
    int x;  
    LONG style;  
    LPCSTR lpszName;  
    LPCSTR lpszClass;  
    DWORD dwExStyle;  
} CREATESTRUCT;  

lpCreateParams
Points to data to be used to create the window.

hInstance
Identifies the module-instance handle of the module that owns the new window.

hMenu
Identifies the menu to be used by the new window. If a child window, contains the integer ID.

hwndParent
Identifies the window that owns the new window. This member is NULL if the new window is a top-level window.

cy
Specifies the height of the new window.

cx
Specifies the width of the new window.

y
Specifies the y-coordinate of the upper left corner of the new window. Coordinates are relative to the parent window if the new window is a child window; otherwise coordinates are relative to the screen origin.

x
Specifies the x-coordinate of the upper left corner of the new window. Coordinates are relative to the parent window if the new window is a child window; otherwise coordinates are relative to the screen origin.

style
Specifies the new window's style.

lpszName
Points to a null-terminated string that specifies the new window's name.

lpszClass
Points to a null-terminated string that specifies the new window's Windows class name (a WNDCLASS structure; for more information, see the Windows SDK).

dwExStyle
Specifies the extended style for the new window.

Header: winuser.h

Structures, Styles, Callbacks, and Message Maps
CWnd::OnCreate