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To change from ‘Normal Mode’ to ‘Full screen Mode’ in Virtual Box is very easy.
From main menu in Virtual Box, select File > Full Screen Mode.
You will have a reminding message before you switch to ‘Full screen Mode’. You can go back to ‘Normal Mode’ at any time by pressing HOST + F.
HOST button in Virtual Box is RIGHT CTRL button.
Now, I’m in ‘Full Mode’ screen.
After I press combination Host + F, now I go back to ‘Normal Mode’.