Abstract

Introduction In a real-time system, many jobs are time-critical. Here, by job, we mean a unit of work to be scheduled and executed. A job may be the computation of a control law, the transmission of an operator command, the retrieval of a file, and so on. To execute, it requires a computer, a data link, a console, and a disk; we refer to them all as processors. The processors are identical if they can be used interchangeably. Otherwise they are functionally dedicated, as exemplified by the processors listed above. The length of time a job requires to complete if it were to execute alone is called its execution time. The execution of a time-critical job cannot begin until its release time and must complete by its deadline. To validate a real-time system, its builder must demonstrate convincingly that all time-critical jobs will always complete by their deadlines, after making sure that the scheduler

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