One of the most significant changes to the Raspberry Pi Model B+ is the 40-pin header (J8). This offers and increase of 14 pins over the 26-pin header on the original Raspberry Pi.
This page aims to provide a set of information that should prove useful to anyone interfacing to these pins in their projects. It also includes a link to a printable PDF worksheet that is useful for making notes as you connect items to your header.
Here is a diagram showing all 40-pins :
The B+ offers 9 extra GPIO pins which can be configured as inputs of outputs. This brings the total number to 26 (17+9).
The extended header offers an additional 3 ground pins. So that’s a total of 8.
Referring to information on a webpage is great but when you are hardware interfacing it is still useful to be able to scribble on a piece of paper. I’ve created a printable Model B GPIO worksheet so that you can draw and write on the diagram as you build your projects.
It makes it much easier to remember what wires, sensors and components you’ve got connected to each pin.