Figure C-1 shows the pinouts for the current 40-pin GPIO Raspberry Pi.
If you have an Raspberry Pi, it is most likely the model B rev. 2 board shown in Figure C-2.
The very first released version of the Raspberry Pi model B (rev. 1) has some minor pinout differences from the rev. 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 C-3.