tailieunhanh - Typical Real - Time Applications

From its title, you can see that this book is about real-time (computing, communication, and information) systems. Rather than pausing here to define the term precisely, which we will do in Chapter 2, let us just say for now that a real-time system is required to complete its work and deliver its services on a timely basis. Examples of real-time systems include digital | Integre Technical Publishing Co. Inc. Liu January 13 2000 8 45 . chap1 page 1 CHAPTER 1 Typical Real-Time Applications From its title you can see that this book is about real-time computing communication and information systems. Rather than pausing here to define the term precisely which we will do in Chapter 2 let us just say for now that a real-time system is required to complete its work and deliver its services on a timely basis. Examples of real-time systems include digital control command and control signal processing and telecommunication systems. Every day these systems provide us with important services. When we drive they control the engine and brakes of our car and regulate traffic lights. When we fly they schedule and monitor the takeoff and landing of our plane make it fly maintain its flight path and keep it out of harm s way. When we are sick they may monitor and regulate our blood pressure and heart beats. When we are well they can entertain us with electronic games and joy rides. Unlike PCs and workstations that run nonreal-time applications such as our editor and network browser the computers and networks that run real-time applications are often hidden from our view. When real-time systems work correctly and well they make us forget their existence. For the most part this book is devoted to real-time operating systems and communication protocols in particular how they should work so that applications running on them can reliably deliver valuable services on time. From the examples above you can see that malfunctions of some real-time systems can have serious consequences. We not only want such systems to work correctly and responsively but also want to be able to show that they indeed do. For this reason a major emphasis of the book is on techniques for validating real-time systems. By validation we mean a rigorous demonstration that the system has the intended timing behavior. As an introduction this chapter describes several representative .