1.AsyncTasks are executed serially on a single background thread on all versions of Android.
2.AsyncTasks execute on a single thread by default from Eclair to Ice Cream Sandwich, and default to thread pool from Jellybean onwards unless programmatically forced to use a single thread. The number
3.AsyncTasks are executed on parallel threads in all cases, but the maximum number of concurrent instances is restricted to 8 up until KitKat.
4.AsyncTasks execute on a single thread by default from Cupcake to Donut, and default to a single thread from Honeycomb onwards unless forced to use a thread pool.