TABLE OF CONTENTS A real-time operating system (RTOS) is key to many embedded systems today and, provides a software platform upon which to build applications. Not all embedded systems, however, are designed with an RTOS. Some embedded systems with relatively simple hardware or a small amount of software application code might not require an RTOS. Many embedded systems, however, with moderate-to-large software applications require some form of scheduling, and these systems require an RTOS.
This chapter sets the stage for all subsequent chapters in this section. It describes the key concepts upon which most real-time operating systems are based. Specifically, this chapter provides
a brief history of operating systems,
a definition of an RTOS,
a description of the scheduler,
a discussion of objects,
a discussion of services, and
the key characteristics of an RTOS.
In the early days of computing, developers created software applications that included low-level machine code to initialize and interact with the system s hardware directly. This tight integration between the software and hardware resulted in non-portable applications. A small change in the hardware might result in rewriting much of the application itself. Obviously, these systems were difficult and costly to maintain.
As the software industry progressed, operating systems that provided the basic software foundation for computing systems evolved and facilitated the abstraction of the underlying hardware from the application code. In addition, the evolution of operating systems helped shift the design of software applications from large, monolithic applications to more modular,...
