I really don’t think Open-AT / ADL is a good platform for learning ‘C’ 
I would strongly suggest that you take time first to learn programming in ‘C’ then, once you are proficient, move on to applying that in Open-AT / ADL.
Some suggestions here: blog.antronics.co.uk/2011/08/08/
Have you studied the ADL User Guide 
In particular, the Flow Control Manager (FCM) section - which explains AT and Data modes?
Save to where?