CHAPTER 20

Influential Operating Systems

Now that you understand the fundamental concepts of operating systems (CPU scheduling, memory management, processes, and so on), we are in a position to examine how these concepts have been applied in several older and highly influential operating systems. Some of them (such as the XDS-940 and the THE system) were one-of-a-kind systems; others (such as OS/360) are widely used. The order of presentation highlights the similarities and differences of the systems; it is not strictly chronological or ordered by importance. The serious student of operating systems should be familiar with all these systems.

In the bibliographical notes at the end of the chapter, we include references to further reading about these early systems. The papers, written by the designers of the systems, are important both for their technical content and for their style and flavor.

CHAPTER OBJECTIVES

  • To explain how operating-system features migrate over time from large computer systems to smaller ones.
  • To discuss the features of several historically important operating systems.

20.1 Feature Migration

One reason to study early architectures and operating systems is that a feature that once ran only on huge systems may eventually make its way into very small systems. Indeed, an examination of operating systems for mainframes and microcomputers shows that many features once available only on mainframes have been adopted for microcomputers. The same operating-system ...

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