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OPERATING SYSTEM STRUCTURE (:<3: MONOLITHIC (:red_flag: A monolithic…
OPERATING SYSTEM STRUCTURE
:<3: MONOLITHIC
:red_flag: A monolithic kernel is an operating system architecture where the entire operating system is working in kernel space and is alone in supervisor mode. The monolithic model differs from other operating system architectures (such as the microkernel architecture) in that it alone defines a high-level virtual interface over computer hardware. A set of primitives or system calls implement all operating system services such as process management, concurrency, and memory management. Device drivers can be added to the kernel as modules.
:red_flag:
https://en.wikipedia.org/wiki/Monolithic_kernel
:red_flag: Fundamental process management
:red_flag:File systems
:red_flag:I/O and device management
:red_flag:Interprocess communication
:red_flag: Hardware
:red_flag:
:<3:LAYERED
:black_flag: Problems
:black_flag:It can be hard to specify and maintain fixed interfaces between the layers.
:black_flag:Layers are sometimes distinguished from Tiers. But the arguments haven't really convinced me. Both layers and tiers make use of their adjacent units. Tiers are often located on different machines, but this is not essential to the architecture.
:
:black_flag:The layered are selected such that each user functions and services of only lower level layer. The first layer can be debugged wit out any concern for the rest of the system. It user basic hardware to implement this function once the first layer is debugged., it’s correct functioning can be assumed while the second layer is debugged & soon . If an error is found during the debugged of particular layer, the layer must be on that layer, because the layer below it already debugged. Because of this design of the system is simplified when operating system is broken up into layer.
:black_flag:The main disadvantage of this architecture is that it requires an appropriate definition of the various layers & a careful planning of the proper placement of the layer.
:black_flag: REFRENCE
http://www.dossier-andreas.net/software_architecture/layers.html
:black_flag: The layered Architecture of operating system was developed in 60’s in this approach; the operating system is broken up into number of layers. The bottom layer (layer 0) is the hardware layer and the highest layer (layer n) is the user interface layer as shown in the figure.
:<3: MICROKENEL
:fire: Mach
example of microkenel
Mac OS X kenel (Darwin) partly based on Mach
:fire: Communication
Takes place between user module using message passing
:fire: Moves as much from the kernel into user space
:fire: Benefits
easier to port the operating system to new architectures
more reliable (less code is running in kernel mode)
easier to extend a microkenel
more secure
:fire: Disadvantage
Perfome overhead of user space to kernel space communication
