why won't my turtle move

[ironsheep]

import turtle
fred=turtle.Pen()
fred=turtle.shape("turtle")
fred=turtle.color("purple")
fred.forward(100)

Error:
  My error message is Traceback (most recent call last):
  File "C:/Users/Mitesh Patel/Desktop/trash.py", line 5, in <module>
    fred.forward(100)
AttributeError: 'NoneType' object has no attribute 'forward'
>>> 

What does this all mean? My turtle should be moving