int pascal GetClassName(HWND hWnd, char *buf, int nMaxChars)

  This function retrieves the class name of a window.

Parameters
  hWnd is the handle of the window to query.
  Buf is a pointer to the user-defined buffer which the class name will
      be copied into.
  nMaxChars is the length of the user buffer.

Returns
  The number of characters copied into the buffer, or 0 if the
function fails.