What is the diff. between as 1.0 and as 2.0

1

Learning a actionscript 1.0 (i m working in flash mx) but there is alos as 2.0.
Which is better for learn.

What is the diff between 1.0 and 2.0 as.

or first i learn 1.0 and then 2.0…

expecting a same reply from great scripter…