For background on the semantics of statecharts and a bit of computer science history, see the following papers and book by Prof. David Harel (the inventor of statecharts) and his collaborators:

The STATEMATE Semantics of Statecharts, 1996

http://www.wisdom.weizmann.ac.il/~harel/SCANNED.PAPERS/Seman...

Modeling Reactive Systems with Statecharts: The STATEMATE Approach, 1998

http://www.wisdom.weizmann.ac.il/~harel/reactive_systems.htm...

The Rhapsody Semantics of Statecharts (or, On the Executable Core of the UML), 2004

http://www.wisdom.weizmann.ac.il/~harel/papers/RhapsodySeman...

Statecharts in the Making: A Personal Account, 2007

http://www.wisdom.weizmann.ac.il/~harel/papers/Statecharts.H...