General Purpose Input Output on the Raspberry Pi

GPIO
Most models of the Raspberry Pi have 40 pins that look like this:

GPIO Pin Numbering
When programming the GPIO pins there are two different ways to refer to them: GPIO numbering and physical numbering. Throughout this course (and in all our resources) we will refer to the pins using the GPIO numbering scheme. These are the GPIO pins as the computer sees them. The numbers don’t make any sense to humans, they jump about all over the place, so there is no easy way to remember them. However, you can use a printed reference, a reference board that fits over the pins or a website guide to help you out.
Teaching Physical Computing with Raspberry Pi and Python

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