More fun with understanding the pi's GPIO using python, and the breadboard (solderless circuit board for prototyping electronics) kit from SK Pang:

• Read http://wrightrocket.blogspot.co.uk/2012/07/python-on-raspberry-pi-gpio.html to get a better understanding of the naming conventions used.

• Connect GPIO18 (pin position 12 - yellow wire in the image) to breadboard connected to LED's positive anode (longer leg). The LED's cathode is connected to a resistor, which is connected to ground on the breadboard. The red wire connects breadboard ground with the GPIO header pin 6, which is ground.

• Install python RPi.GPIO via: sudo apt-get install python3-rpi.gpio

• Pilfer simple python program from https://github.com/wrightrocket/PythonOnTheRaspberryPy, and save as e.g. led.py

import time
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM) # use formal names, not pin positions
GPIO.setup(18, GPIO.OUT) # set GPIO18 to be output rather than input

for TIMES in range(10):
     GPIO.output(18, True) # enable GPIO18
     time.sleep(1)
     GPIO.output(18, False) # disable GPIO18
     time.sleep(1)

• run script (as root: GPIO is privileged) sudo python3 led.py
• the LED will flash on for a second and off for a second in a loop 10 times.

Takeaway: GPIO allows programmatic control of the input/output pins on the Pi. There are python, C, Java and assembler (any more?) options for controlling GPIO on the Pi.