Evolving toward Ada in real time systems

The Ada view of multitasking represents a radical departure from the traditional “cyclic executive” approach to real time operating systems. Since system designers must by necessity be conservative, it would be unrealistic to expect an abrupt change of this magnitude in engineering practice. Instead, this paper outlines a sequence of intermediate steps designed so that the advantages and familiar structures of cyclic systems may be retained, while the capabilities of Ada multitasking are gradually incorporated. A scale of increasing scheduling complexity provides the justification for this sequence. The discussion of each step then briefly mentions some of the related benefits and costs. The paper draws some conclusions about the use of Ada in real time systems.