5.1 Introduction

Simple software applications are typically designed to run sequentially, one instruction at a time, in a pre-determined chain of instructions. However, this scheme is inappropriate for real-time embedded applications, which generally handle multiple inputs and outputs within tight time constraints. Real-time embedded software applications must be designed for concurrency.

Concurrent design requires developers to decompose an application into small, schedulable, and sequential program units. When done correctly, concurrent design allows system multitasking to meet performance and timing requirements for a real-time system. Most RTOS kernels provide task objects and task management services to facilitate designing concurrency within an application.

This chapter discusses the following topics:

· task definition,

· task states and scheduling,

· typical task operations,

· typical task structure, and

· task coordination and concurrency.