Figure B-1 shows the pinout for the current 40-pin general-purpose input/output (GPIO) Raspberry Pi.
If you have a Raspberry Pi, it is most likely to be a model B revision 2 board, as shown in Figure B-2.
The very first released version of the Raspberry Pi model B (revision 1) has some minor pinout differences to the revision 2 that followed. This is the only version of the Raspberry Pi that is not compatible with later pinouts. The incompatible pins that changed are highlighted in bold in Figure B-3.