From raspberrypi.org's GPIO page:
%%blockquote
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 (unpopulated on Pi Zero and Pi Zero W).
%%
[{Image src='attach/GPIO/raspberry-pi-pinout.png' caption='The Raspberry Pi GPIO Pinout (courtesy pinout.xyz)' align='center'}]
----
You can type:
{{{
% pinout
}}}
in the Raspbian OS and it will display information about your GPIO usage.
!! Links
* [Interactive GPIO Pinout|https://pinout.xyz/#]
* [GPIO|https://www.raspberrypi.org/documentation/usage/gpio/] page on raspberrypi.org
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[{Tag Hardware GPIO}]