Summary

The operating system provides a number of management activities to the running processes and their needed resources such as main-memory, files, I/O devices and secondary storages. System calls are the basic functions to control and manage processes and system resources. As the operating systems were developed, different structures are adopted. Historically, the operating system structure has a simple structure. As the operating system has a large size, other structures were used such as layered and microkernels. The modular structure applies the object-oriented approach as a modern approach. The concept of virtual machine was developed to allow more than one operating system to be used on one machine. During the operating system design, a separation is needed between the mechanism and policies. When the operating system is installed for a particular machine, system generation is performed.