Processes
An entity that can be assigned to and executed on a processes,
Multiprogramming, time-sharing and real-time transaction systems lead to the refinement of the concept of process.
A process can be defined by its attributes and behaviors : it can be viewed as an Abstract Data Type (ADT).
When instances of this ADT co-exist we have concurrent processing.
Issues in concurrent processing : synchronization, mutual exclusion, deadlock, communication.