Describe Layered Structure of Operating System | Operating System Question & Answer

The modules of the operating system are divided into several layers stacked one above the other, thus forming a hierarchical structure. The lowest layer (Layer 0) interacts with the underlying hardware and the topmost layer (Layer N) provides an interface to the application programs/ users. Only adjacent layers can communicate with each other. A layer N can request for services only from a layer immediately below it (layer N-1).  A layer N can provide services only to the layer immediately above it (layer N + 1). A Layer only needs to know what services are offered by the layer below it. In this structure any request that requires access to hardware has to go through all layers. Bypassing of layers is not allowed.

Advantage:   

 This approach makes it easy to build, maintain and enhance the operating system.  

 Locating an error is easy as system can start debugging from 0 layer and proceed further covering entire system if required. 

Disadvantage:  

 Overall performance speed is slow as requests pass through multiple layers of software before they reach the hardware.

Or