To interrupt program execution during a debugging session, click on the
  Stop push button on the push-button view in the main window.  This is
  useful if, for example, the program is in an infinite loop.

  To abort a debugger operation in progress, click on Stop.  This is
  useful if, for example, the debugger is displaying a long stream of
  data.

  Clicking on Stop does not end the debugging session.  Clicking on Stop
  when the program is not running or when the debugger is not doing an
  operation has no effect.