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The correctness of many systems and devices in our modern society depends not only on the effects or results they produce but also on the time at which these results are produced. These real-time systems range from the anti-lock braking controller in automobiles to the vital-sign monitor in hospital intensive-care units. For example, when the driver of a car applies the brake, the anti-lock braking controller analyzes the environment in which the controller is embedded (car speed, road surface, direction of travel) and activates the brake with the appropriate frequency within fractions of a second. . | Real-Time Systems Scheduling Analysis and Verification. Albert M. K. Cheng Copyright 2002 John Wiley Sons Inc. ISBN 0-471-18406-3 CHAPTER 1 INTRODUCTION The correctness of many systems and devices in our modern society depends not only on the effects or results they produce but also on the time at which these results are produced. These real-time systems range from the anti-lock braking controller in automobiles to the vital-sign monitor in hospital intensive-care units. For example when the driver of a car applies the brake the anti-lock braking controller analyzes the environment in which the controller is embedded car speed road surface direction of travel and activates the brake with the appropriate frequency within fractions of a second. Both the result brake activation and the time at which the result is produced are important in ensuring the safety of the car its driver and passengers. Recently computer hardware and software are increasingly embedded in a majority of these real-time systems to monitor and control their operations. These computer systems are called embedded systems real-time computer systems or simply real-time systems. Unlike conventional non-real-time computer systems real-time computer systems are closely coupled with the environment being monitored and controlled. Examples of real-time systems include computerized versions of the braking controller and the vital-sign monitor the new generation of airplane and spacecraft avionics the planned Space Station control software highperformance network and telephone switching systems multimedia tools virtual reality systems robotic controllers battery-powered instruments wireless communication devices such as cellular phones and PDAs astronomical telescopes with adaptive-optics systems and many safety-critical industrial applications. These embedded systems must satisfy stringent timing and reliability constraints in addition to functional correctness requirements. Figure shows a model of a .