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The concept of a modern hierarchical state machine introduced in Part I is to event-driven programming as the invention of a wheel is to transportation. But just as wheels are useless without the infrastructure of roads, state machines are useless without an event-driven infrastructure that provides, at a minimum, a run-to-completion execution context for each state machine, queuing of events, and event-based timing services.

In Part II of this book, I describe such a reusable infrastructure for executing concurrent state machines in the form of a real-time framework called QF. QF is tailored specifically for developing real-time embedded (RTE) applications and in many respects resembles a real-time operating system (RTOS). Part II begins with Chapter 6, which introduces the real-time framework concepts. Chapter 7 describes the QF structure and implementation. Chapter 8 is devoted to porting and configuring QF, providing examples of using QF in a bare-metal system, with a traditional RTOS, and with a conventional OS (Linux). Chapter 9 describes how to develop QP applications that utilize both the QF framework and the QEP event processor described in Part I of this book. Chapter 10 presents a tiny preemptive, run-to-completion, real-time kernel called QK that beautifully complements QF. Chapter 11 describes a testing and debugging strategy based on software-tracing instrumentation built into all QP components. Chapter 12 concludes the book by presenting an ultralight version of the framework and the hierarchical event processor called QP-nano.