The "X" marker/button at the extreme upper right hand corner of all windows is provided by the window manager software. Clicking "X" on RunControl will close the RunControl session. You should only close the RunControl session while in the START state. Exiting RunControl while not in the START state may lead to unpredictable system behaviour, and should be avoided at all costs. If you are not in the START state, you will be prompted to confirm the exit. If you do not close the partition before exiting the RunControl session, then your partition will be closed for you. You can also exit RunControl via the Exit option in the File pull-down menu.