Programming language • Add parallel composition to Hongseok’s sequential language: • Interleaving semantics:

Concurrent programming is hard “If you can get away with it, avoid using threads. Threads can be difficult to use, and they make programs harder to debug.” Java Sun Tutorial “Threads and Swing” Multi-core means concurrency everywhere! Verifying concurrent programs is even harder • Later this week: several logics for this • Bottom-line: Informal reasoning principles that you can use to develop correct concurrent programs • This talk: background on concurrenc