Operating Systems Design and Implementation (3rd Edition)

1.7. Summary

Operating systems can be viewed from two viewpoints: resource managers and extended machines. In the resource manager view, the operating system's job is to efficiently manage the different parts of the system. In the extended machine view, the job of the system is to provide the users with a virtual machine that is more convenient to use than the actual machine.

Operating systems have a long history, starting from the days when they replaced the operator, to modern multiprogramming systems.

The heart of any operating system is the set of system calls that it can handle. These tell what the operating system really does. For MINIX 3, these calls can be divided into six groups. The first group of system calls relates to process creation and termination. The second group handles signals. The third group is for reading and writing files. A fourth group is for directory management. The fifth group protects information, and the sixth group is about keeping track of time.

Operating systems can be structured in several ways. The most common ones are as a monolithic system, as a hierarchy of layers, as a virtual machine system, using an exokernel, and using the client-server model.