The Raspberry Pi (A/B model) has 26 GPIO 1) soldered pins and 5 GPIO pins that you need to solder. These may be used to control electronics connected to the Raspberry Pi. Among the things that can be done are:
It is important to know how these pins can be accessed. For the Raspberry Pi, Wyliodrin uses the WiringPi pins layout described in the picture below. Place the Raspberry Pi with the SD Card faceing upwars.
As it can be seen, not all the pins may be used for anything. There are:
Out of these pins, only one pin has hardware PWM.