As an example, consider processing a request like withdrawing money. It is a financial transaction, which requires updating accounts within an acceptable response time. Both the process control systems and transaction oriented systems are real time systems in which the response time to a request is critical. The main objective is to assure timeliness in response. The transaction oriented systems may even use the computer network extensively and often. The process control systems may be bus based or may have local area network as well. Both these systems invariably recognize an event and offer a response. In a transaction oriented system like ATM,it may be a card input. In a process control system an event may be detected when the temperature in a process vessel exceeds a certain limit. The operating system used in such real-time systems is often referred to as RTOS. In addition, to the above kind of systems, we are now witnessing emergence of a class of systems that are embedded within an application. For instance, it is not unusual to find up to four microprocessors in a car. These may be used for regulating fuel injection, cruise control or even operation of brakes. Similarly, there are microcontrollers embedded in washing machines. The presence of these systems
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