Cam flaps back into his classroom, collects his seventh-years, and hauls them out to the edge of the lake too.

Slightly farther than the replica of his house.

He doesn't have a building set up here. Just mud and weeds.

"Who here wants to guess what things will be different between now and the year 2159?"

The seventh years had much higher uptake of the name tags. Daniel Hornbeam raises a hand and guesses, "Different countries? I mean, some countries will split up and combine and stuff."

"Excellent guess! Yes!"

His freshly-reinstalled-AGAIN chip commands the hologram projector he mostly hid under the mud to activate and now they are standing around a projection of a political globe of Earth.

"Any other guesses?"

"Well apparently the muggles are going to invent illusions," says another student (Mallory) while she sticks her hand in the globe. "And probably some other things too, I reckon. Like spaceships?"

"Yes, a little farther into the term we will be going on a field trip to the moon." Slide. Now they are in an illusory spaceship.

Everyone is immediately distracted by the illusory spaceship controls! Except Percy Weasley, who asks, "Is this illusion made with a computer? I heard muggles are working on better computers."

"Yes, there are computers involved! I'm controlling them with a device in my brain. Now in this universe, computer engineers don't have the benefit of magical help, so you can expect the trajectory to be a bit different from the one in my universe - the device in my brain was invented by a demon, like me, not a regular human - but I can nonetheless assure you that computers will be big."

"You have a device in your brain?"

"Doesn't that hurt?"

"Can humans get those? I'm not saying I want one, mind."

"I have a device in my brain! It looks like this." He makes one outside his brain for them to pass around. "It doesn't hurt, because all the nerves that register pain are outside of your brain sending messages to your brain; the brain itself can't feel a thing. People are usually awake the whole time if they're getting brain surgery even if it's the kind where they have their skulls cut open. Humans can get these, but I don't know if wizards can - even if you planned never to set foot anywhere as interferingly magical as Hogwarts again in your life, I'm not a neuroscientist and have no way to find out confidently if your brains are just like Muggle brains in the relevant respects."

This sparks some speculation about whether wizards' brains are different from muggles' brains, but none of them are neuroscientists either and it doesn't go anywhere. What else can computers do, besides being controlled by thoughts and making illusions?

"Let's see if I can make it relevant to, not your lives, but your fields. Somebody tell me what you wanna do when you grow up."

"I want to work at the Ministry!" says Percy excitedly. "Probably in the Department of Magical Law Enforcement but the Department of International Magical Cooperation does excellent work too."

"Lot of filing, meetings, looking things up and writing things down?"

"Yes!" he says like that's the coolest and most important thing in the world.

"Well, let's see. A Muggle office in this calendar year probably looks like this," cube farm. "That's a current-year computer over there. Have you guys covered computers yet?"

"A bit? They use electricity and can do sums and I think they're related to typewriters?"

"You can write things on them that you can write on a typewriter."

"Yeah, that was it."

"And that over there is a printer! Once you've written something on it you can make the printer make a copy, as many as you have the paper and ink for. But you can also cause the file you've written to appear on another computer! Some offices use little to no paper."

Percy's brow furrows. "No paper? Wouldn't you have to carry your computer around to all your meetings, then? And how do you keep it all organized on there?"

"Well, computers take up less space as they get more advanced. This is mine." He waves his little stick of a computer. "They get small enough to fit in a briefcase soon. Also, instead of sending it to a printer, you could send it to be copied to a little computer-readable storage item, so another computer at your destination can read it from there. How are you imagining it being disorganized, exactly?"

"What's the computer equivalent of having all your papers alphabetized in the correct folders in a filing cabinet, and new incoming papers in your in-tray?"

Slide. Now they are being presented with a blown-up computer interface. "Computers can be programmed to act like they're a filing cabinet! But there are some advantages over that. Within a notional 'folder', you can sort stuff by several different parameters - date created or date edited, file type in case some of them aren't text but are pictures or audio or something, alphabetical by name. Also, you can have the computer look through every single file you have, looking for, say, the word 'Paraguay', or, if you're really fancy, you can have it find you all files that were created in a specific month and have a photo in them and say Paraguay in the file name, that kind of thing."

Percy stares. "How efficient! I look forward to computers getting small enough that the Ministry starts using them." (He also kind of wants one for his homework, but of course it would die as soon as he went back to the castle.)

"Oh, do electronics work there? That's great! They'll be getting both less bulky and better at what they do basically indefinitely. You do want to watch out for that, because if a big institution adopts computers early and then computers get better and they don't keep up, they wind up with legacy systems that interface poorly with everything else. Banks and governments had this problem a lot in my turn of this century. Okay, who else has a career in mind?"

"I want to work on the wizarding wireless!" says Mallory. I don't mean as one of the people who go on the wireless, I mean one of the people who keep the spells for it working."

"The wireless is like the radio only it doesn't use radio frequency?"