A powerful feature of the Raspberry Pi is the row of GPIO (general-purpose input/output) pins along the top edge of the board. A 40-pin GPIO header is found on all current Raspberry Pi boards although it is unpopulated on Raspberry Pi Zero, Raspberry Pi Zero W, and Raspberry Pi Zero 2 W. The GPIO headers on all boards have a 0.1-inch (2.54 mm) pin pitch. Any of the GPIO pins can be designated in s
![Raspberry Pi Documentation - Raspberry Pi hardware](https://cdn-ak-scissors.b.st-hatena.com/image/square/7ed6aef5c23961f2d8437ff1525a2dd813d92a31/height=288;version=1;width=512/https%3A%2F%2Fwww.raspberrypi.com%2Fdocumentation%2Fimages%2Fopensocial.png)