You need a global variable to hold the window handle of the edit control. Add the following statement to the beginning of the C-language source file:
HWND hEditWnd /* handle to edit window */
You also need a local variable in the WinMain function to hold the coordinates of the client-area rectangle. These coordinates are used to determine the size of the control. Add the following statement to the beginning of the WinMain function:
RECT Rect;