Raspberry Pi Zero was built to access the outside world. Much of this access is available through the GPIO pins. Let's start by detailing what the GPIO pins are and what they can do. Raspberry Pi Zero has 40 GPIO pins.

Here is a closeup of the 40 pins:

Here is a listing of the pins and their connection to the Raspberry Pi Zero:

The purpose of some of these pins is very clear. Pins 1 and 17 are available to supply 3.3 volts, pins 2 and 4 supply 5 volts, and pins 9, 25, 39, 6, 14, 20, 30, and 34 are all connected to ground on Raspberry Pi Zero. The rest of the pins have various capabilities, which you'll learn in this chapter. Let's start with the pins that can be used to supply a simple DC signal to the outside world.