Each server process has its lown address space and

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Unformatted text preview: arious components of an operating system in the sections above. We will now have a look at how these components are put together to form an operating system. Layered Structure Most modern operating systems organize their components into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0) is the hardware, and the highest layer (layer n) is the user interface. The number of inbetween layers and their contents vary from one operating system to another. How this is decided is explained below. The main advantage of the layered approach is modularity. The layers are selected such that each layer uses the functions and services provided by its immediate lower layer. This approach greatly simplifies the design and implementation of the system because each layer is implemented using only those operations provided by its immediate lower level layer. Kernel The kernel of an operating system is its central controlling part that implements the most primitive of the system's functions. It is the only part of an operating system that a user cannot replace or modify. The precise interpretation of the system's functions that are part of the kernel varies from one operating system to another. However, typical operating system kernels contain basic functions that are required for process management, memory management, device management, and low-level security features like access control. In some systems, the kernel is larger and provides for more than these functions, whereas in others, it is smaller. Monolithic Kernel versus Microkernel The two commonly used models for kernel design in operating systems are the monolithic kernel and the microkernel. In the monolithic kernel model, most operating system services such as process management, memory management, device management, file management, and security are provided by the kernel. As a result, the kernel has a large, monolithic structure. On the other hand, in the microkernel model, the main goal is to keep the kernel as small as possible. Therefore, in this model, the kernel is a very small nucleus of software that provides...
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This document was uploaded on 04/07/2014.

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