Layered Systems

 Layered Systems:

In the layered system structure, operating system is organized as hierarchy of layers, each of the layers is constructed upon one another. The first system constructed in this way was the THE system built at the Technische Hogeschool Eindhoven in the Netherlands by E. W. Dijkstra and his students. The THE system was a simple batch system for a Dutch computer. Layer 0 assign with allocation of the processor, switching between processes when timers expired. 

 

Above layer 0, the system consisted of sequential processes, each of which could be programmed without having to worry about the fact that multiple processes were running on a single processor. In other words, layer 0 provided the basic multiprogramming of the CPU.

Layer 1 was used to the memory management. It distributed space for processes in main memory used for holding parts of processes. Layer 1 was taking care of making sure pages are transport into memory whenever they are needed.

Layer 2 handled communication between each process and the operator console. On top of this layer each process effectively had its own operator consol.

Layer 3 It takes care of managing the input/ output devices and buffering the information streams to and from them.

Layer 4 This is the highest layer in the layered operating system. This layer deals with the many user programs and applications that run in an operating system such as word processors, games, browsers etc.