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

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

14