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On the https://processing.org/tutorials/gettingstarted/ page, it says:
So far we've covered only the Run button, though you've probably guessed what the **Stop **button next to it does...
Change Show to Stop.
This is a volunteer forum. We aren't the Processing overlords.
I'm not convinced that's a typo. The whole section is admittedly rather poorly worded, but I could see that being the "Show" section, with both the "Stop" and "Present" buttons being discussed.
But Processing is open-source, including its tutorial pages. So you can make this change yourself: https://github.com/processing/processing-docs/blob/master/content/static/tutorials/gettingstarted/index.html