We develop a simulation executor and modeling framework for automated manufacturing systems. An automated manufacturing system is decomposed into a number of subsystems where each system interacts with each other. Each subsystem corresponds to an object in the simulation program that each object has its own data structure and processes. A process is an appropriate abstraction of the primitive events and activities that are performed by an object; Interactions among the subsystems are modeled as interactions among concurrent processes of the corresponding objects. A simulation executor that handles process interactions is developed using a single-thread programming language, C++, and the coroutine programming techniques. A modeling framework that is compatible with the executor is proposed. Several modeling examples are presented.