I have a Mac. It has a power adapter: The plug that goes into the power outlet looks like this: I am in Oslo. Their power outlets look like this: I brought a universal adapter with a double-round mode: but its input looks like this: Whoops: a North American plug with a round ground pin won't fit. My old Mac adapter fit—it didn't have the ground pin, just two flat power pins that folded down into the brick. That's why I thought this would work, but no, I upgraded my power adapter, and it broke backward compatibility. Luckily, the shop at Heathrow Airport sells gadgets that have UK output pins: and three-pin round-ground North American input slots: which means I can cobble this together to recharge my laptop: Tomorrow, I will show this to students in the workshop I'm teaching and ask, "Does your software look like this?"