What Is Data Hierarchy?

A hierarchy is an organizational structure of an operating system that provides a model that isolates the functions of each layer of the operating system. It includes the ownership hierarchy hierarchy-attribution hierarchy dimension hierarchy hierarchy hierarchy database hierarchical database and so on.

Hierarchy

Hierarchy(

It is a group of hardware or software projects divided according to the type, level, priority, etc. of the information and arranged according to specific rules.

The biggest feature of this structure is to decompose a large and complex system into several unidirectionally dependent layers, that is, each layer provides a set of functions and these functions only depend on the layers within the layer. The innermost layer is the system core, which has the functions of primary interrupt processing, external device drivers, switching processors between processes, and implementing process control and communication. Its purpose is to provide an environment where processes can exist and move. Outside the system core are the storage management layer, the I / O processing layer, the file access layer, the job scheduling layer, and the resource allocation layer. They have various resource management functions and provide users with various services.

The hierarchical organization structure is only used as a guiding principle in some operating systems, because how to divide the functions of the operating system and how to determine the content and call order of each layer is very difficult.

The classic case of a layered operating system is the THE system of Dijkstra. The design goal of this system is to achieve an operating system that can prove its correctness, and its levels are shown in the table. The layered approach provides a model that isolates the functions of each layer of the operating system. Hierarchical structure restrictions are too strict for today's operating systems, and almost no operating system is constructed in this way. However, when designing the operating system, the layered thinking method is worthy of reference and reference.

Fifth layer user program

Layer 4 input / output management

Third level operator console

Second-tier storage management

First-tier CPU scheduling and signals

Tier 0 hardware facilities

Table: The layered architecture of the operating system