Page 22 - OS | TOPIC 1 | INTRODUCTION TO OPERATING SYSTEM
P. 22

Layered Structure








































             Operating system that groups the related functionality together

             and separates those unrelated.

             Each layer (level) of the operating system is constructed on top

             of  a  lower  layer.  The  user  interface  is  layer  N,  whereas  the


             hardware is layer 0, at the bottom.

             Layers  are  chosen  with  modularity,  only  lower-level  layers'

             functions and services are used by each layer.

             Hiding information at each layer.

             Guidelines for applying the layers are as follows:


             i. user interface layer will be the outermost layer.

            ii. the hardware layer will be the innermost layer.

           iii. certain layer has access to every layer below it, but having no

      access to any layer above it.

             Examples  of  layered-based  operating  systems:  UNIX,  THEOS,

             VMS












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