After Effects - How do I create animated coding
I dont know of any tutorials off hand (you will need to do a google) but to animate text to make it look as if its typing on isnt too hard:


Create your text layer
Expand the later (clicking the white triangle next to the name)
Click on the animate button > select Opacity
Now you can use the range selectors to animate what is changed.


There is also a typewriter preset in the Effects and Presets panel which does the same thing.