Library /sys$common/syshlp/dbg$uihelp.hlb DEBUGUI, windows_menus  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  By default, the debugger starts up in the main window, which includes a
  source view, a push-button view, and a command view.

  When you start the debugger with the command DEBUG/KEEP from DCL level,
  the source view is initially empty.  You can then bring a program under
  debugger control.