How does a tiny board work as a computer?

The full narration of the video.

How can a board the size of your palm count as a whole computer? It's called a Raspberry Pi, about as big as a bank card. No case, no hard drive. Hook up a screen and a keyboard, and you can browse the web and watch videos. To see how it works, picture the board as a tiny kitchen.

The square chip in the middle is the cook. It does the thinking, billions of steps every second. The chip beside it is the cutting board, the memory. Whatever's being cooked sits there, and it's wiped when the power goes off. The fingernail-sized memory card is the fridge plus the recipe book. The system and your files live there. They stay put when the power's off.

In a desktop PC, each of these is a big separate part, plus a large motherboard, a case and fans. The Pi borrows the phone's trick: the part that computes and the part that draws the screen share one chip. That's why it's small and cheap. On the real board, the middle chip is called a system on a chip. A Raspberry Pi 5 has four cores inside, like four cooks working at once.

So in the first second after you plug it in, who moves first? Not the cook. The graphics part of the chip wakes up first. Like a manager, it unlocks the door and turns on the lights. It reads a small startup program stored on the board, then finds the system on the memory card and carries it onto the cutting board.

Only when everything's ready does it wake the cook. The cook follows the recipe line by line, and the desktop appears on the screen. Why does the manager go first? The Pi's very first chip was designed for TV set-top boxes, where the picture mattered most. So far, it's much like any computer. What makes it special is the double row of tiny pins along the edge.

There are forty of them. A program can switch any one of them on or off. Wire up a small light, and it glows when the pin turns on. Wire up a button, and the program knows when you press it. Add a motor, and a little car rolls. These pins are the kitchen's serving window. The cook's decisions get passed out here and turn into lights and spinning wheels. Their real name is general-purpose input/output.

That's why some people call the Pi a microcontroller. Strictly speaking, that's not quite right. A microcontroller is like an automatic egg boiler: one program, loaded once, doing the same job whenever it's on. The Pi is a whole kitchen, and you can swap recipes any time. A computer that can also run lights and motors. That's why it's in weather stations, robots and little home servers, with tens of millions sold.

In one line: it squeezes a whole computer kitchen onto one card. What was the first gadget you ever took apart?